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Foundation Repair InformationInformaton | Maintenance | Underpinning
Foundation Maintenance
By: W. Tom Witherspoon, P.E.
|| Slope Maintenance || Earth Perimeters || Flat Work || Flower Beds ||
|| Gutters And Downspouts || Sub-Surface Drains || Capillary/French Drains ||
|| Irrigation/Sprinkler Systems || Vegetation And Trees || Plumbing Leaks ||
|| Reinforcing Steel Exposure || Brick, Rock Or Cladding Cracks || Vent Covers ||
|| Animal Damage || Termite Damage || Interior Doors ||
A study of failed foundations (ADSC 2000) estimates the cost of foundation repair at over 12.5 billion
dollars annually. The most common cause of foundation failure/problems is poor maintenance, which can
normally be prevented. Considering that most remedial action will not completely keep a foundation from
moving, it becomes even more important that the homeowner complies with the required maintenance .
procedures to reduce movement and allow the house to function as originally intended. This is just as
important after repairs have been complete because the house may move in an area that has not been
repaired or is still dependent upon bearing soil stability for continued performance. Since many
foundation repair companies require homeowner maintenance as a condition of their warranty agreement,
compliance is also good business and one of the best insurance policies available.
The following categories of maintenance are the most common problem areas and should be addressed in
a scheduled sequence to reduce movement before and after foundation repairs to minimize distress in the
foundation and the structure it supports.
Slope Maintenance
The foundation should have been installed sufficiently above site grades to allow proper post-construction
surface drainage. It is the homeowner's responsibility, however, to maintain these positive drainage
conditions. The primary function of good drainage is to prevent ponding near, or intrusion of water, under
the structure, which would increase seasonal moisture fluctuations, or migration of water. Much of the
damage caused by expansive soils is due to lack of timely maintenance by the homeowner and is in some
part preventable.
Under ideal conditions the slab will maintain its original position. Unfortunately soil is not consistent and
the moisture content is seldom at an optimum level in the support soil when the slab is constructed. Many
slabs are poured on drier than normal soil that later becomes wet from capillary rise of water from below,
causing the thin floors to lift. After repeated drying and rewetting of the support soil, small amounts of
soil are squeezed from the interface of the concrete base and the soil base to lower the wall into the
ground, much like a car tire miring into a rut. If the soil has a high amount of clay con- tent, it will also
deform under pressure, much like children's putty during the swelling stage.
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Earth Perimeters
The excavated area outside the foundation is usually filled with loose soil fill when a house is constructed.
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This is usually called the "backfill area". Maintaining a positive slope in the backfill area next to the house
is the most critical aspect of slope maintenance. During the first few months or years, this material often
settles. In many cases settlement is severe enough to reverse or flatten the slope next to the foundation.
Reverse or negative drainage will cause ponding of water during precipitation or heavy irrigation.
Ponding allows an excessive amount of water to percolate into the ground" next to the foundation, which
may accelerate this settlement. To avoid this, the homeowner should periodically com- pact the backfill
area by tamping with a heavy piece of wood such as a 4 "x4 " . Hand compaction works best after a rain
or snow melt has dampened the ground or with the careful addition of small amounts of water by the
home- owner such as with a drip line. Additional soil should be added as necessary to maintain a positive
slope away from the foundation. This soil should always be clay, not sand, so moisture can be better
maintained and water will run off instead of soaking in spotty high concentrations.
Rhe minimum slope requirement should be 5% for the first 5' away from the foundation (3" of drop) and
then at a minimum discharge slope of 1% (approximately 1/8" drop for every foot of distance) from that
point on. The type of vegetation may dictate a greater slope to avoid over saturation of the critical
perimeter soil. Some type of ground cover is recommended, however, to reduce erosion and lower the
frequency of slope maintenance work.
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Flat Work
One of the beneficial functions of flat work {sidewalks and patios that are not part of the foundation)
adjacent to foundations is the prevention of evapotranspiration and fluctuation of water intrusion to the
bearing soils. Therefore, every homeowner should conduct a yearly inspection of concrete flat work and
do any maintenance necessary to improve drainage and minimize infiltration of water from rain, snow
melt and lawn watering. This is especially important during the first five years for a newly built house
because this is usually the time of most severe a9justment between the new construction and environment.
The process of inspection and maintenance should continue over the years, but, cracking, settling and
other problems should become less common.
Because perimeter fill material may not have been compacted in 4" lifts at optimum moisture (as is
normally recommended by engineers), settlement is greater along the house. A negative slope may occur
that will allow ponding. This concentration of water wiII allow permeation through cracks in the concrete
and over- saturation of perimeter bearing soils. This deeper saturation will often times cause damage to
the foundation and/or basement floors. Because evaporation is limited by the flat work, the ponded water
may dramatically increase moisture levels at the crucial perimeter beams and/or piers.
When this tilting of flat work occurs, the concrete should be replaced or mudjacked to reverse the
negative slope. If a minimum of 1 % slope (again about 1/8" for every foot of distance) is maintained,
however, it will only be necessary to seal all cracks and ports of entry to prevent vertical water migration.
This will include the perimeter joint around the foundation grade beam. A urethane or other flexible
sealant should be used that will allow some movement but prevent water passing below the slab.
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Flower Beds
Changing the site by the addition of flower beds, patios, fences,
swimming pools, etc., may cause water ponding, which will exacerbate
the wet cycles. Therefore, proper drainage considerations during such
additions must be made.
Nurserymen will specify peat, bark, sandy loam and other planting
substances, which, in conjunction with bed borders, will increase moisture
levels above that desirable. Therefore, flower beds must have some
provisions for elimination of excess water. This may be in the form of
weep holes, drain barriers or other removal systems. The problems
created by flower beds are not a popular subject since homeowners will
resist good engineering to beautify their house. There should be a balance
between vegetation utilized for aesthetic demands and harming the
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bearing soils.
One of the primary problems in flower bed design is installation of a
concrete or steel barrier that will resist normalwater run-off. If these
barriers are desired, they should have openings cut to allow water passage
and avoid over-saturation.
The use of highly permeable materials
such as peat, bark, etc., should only be
used if topography allows installation of
subsurface drainage to collect excess
water and discharge it away from the
foundation. This will also require
installation of an impermeable barrier at
the bottom of the flower bed to help collect water for removal by the drain
medium.
Shrubs planted in the flower bed should be chosen for their compatibility
to the shallow barrier of the bed. Short and very contained root growth
will be a plus to proper health and maintenance of the bed vegetation.
In the flower bed, the slope should be a minimum of 5% (5/8" for every foot of distance), unless ample
subsurface drainage can be created to discharge water away from the foundation.
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Gutters And Downspouts
Gutters should be inspected twice a year,
once in the spring and again in the fall. All
debris should be cleaned out and metal
gutters checked for rust. If there are trees near
the roof, gutters may have to be cleaned out
more often.
Check the slope of the gutters, since poor
slope causes water to accumulate in low
spots, building up debris and accelerating
rusting. Slope of the gutters should be a
minimum of 1" of fall for each eight feet of
length. The gutter can be installed so that it
drains in one direction. If, however, any
single length of gutter is more than 35' long it
should be installed to drain both ways from
the center or have downspouts at a spacing of
not more than 20' on center.
The easiest way to check the slope of a gutter
is to use a garden hose or pour a bucket of
water into it and see if the water flows out
smoothly or ponds in low spots. The gutter should then be adjusted to remove any high or low spots that
prevent the smooth flow of water.
Downspouts should be checked for clogging at the same time the gutters are checked. Clogging often
occurs at the elbow where downspout and gutter meet. The elbow can be removed for cleaning, but it may
be necessary to use a plumber's snake to clean the down- spout. If there is a problem with leaves, a leaf
strainer or leaf guard is a good buy as long as neither prevents proper function of the gutter.
Splash blocks should be long enough and sloped enough to carryall water well away from the foundation
and beyond the backfill area. Water should be discharged no closer than 5' from the foundation. Usually it
is necessary to add a downspout extension in order to get the water far away from the foundation. It is
possible to purchase extensions that have flexible elbows that can be bent up to make it easier to mow the
lawn. The extensions should be left down at all times. Special roll-up type down- spout sheets (plastic
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tubes) that attach to the end of the downspout are also available. These plastic tubes extend when filled
with water and roll up when empty. If erosion is a possibility, splash blocks can be placed at the discharge
point to prevent associated problems.
Because the materials delineated above are readily accessible at most hardware and do-it- yourself stores
in a variety of makes and colors, they can add to the aesthetic qualities of a house.
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Sub-Surface Drains
Subsurface drains will many times be utilized when topography, vegetation or construction does not make
it possible to drain at the surface. These may consist of drain inlet basins, trench drains, funnel drains, etc.
If correctly installed, subsurface drains should require little maintenance. The most important thing to
remember is to avoid covering or obstructing the drain where it discharges and to maintain adequate
slope. It may occasionally be necessary to clean out roots, nests or other debris from inlet basins or
discharging ends of the pipe.
Inlet basins should be inspected every 6 months to ensure these do not become clogged with leaves, grass,
soil or other debris, which would negate function. The bottom of these inlets normally has a sedimentation
basin that requires removal of dirt as fill adds up over time. It may also be necessary to back wash (main
lines when discharge becomes a noticeable problem. If problems persist, running of a( mechanical snake
may be necessary to remove 1 the obstruction.
Settlement problems in a yard will many I times crush piping and reduce the discharge I flow, which will
cause sedimentation to occur and subsequent closure of the drain lines. Damage may also result from the
driving of heavy trucks across the surface. In any case, repair will normally require excavation and
replacement of the drain line. This may be an even greater possibility if clay tile is used in lieu of heavy
duty pvc.
Location of clean-outs and discharge lines will be a plus to locate problems and initiate corrective action.
Therefore, a drawing of lines and locations should be made during installation for future reference.
|| Top of Page ||
Capillary/French Drains
Capillary drains are installed to intercept and collect moving subsurface
water and discharge it away from the structure. Unless the slope allows,
this will many times require installation of a deep sump and pump to
collect water and discharge it through a shallow drain line.
The pumps utilized in this operation may
malfunction and unless an alarm system is
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installed there will be no warning.
Therefore, it is advisable that the
homeowner inspect the sump at least
every 6 months to make sure trash, debris
or pump failure has not occurred. If a solid sump well cover is used, there
will be less potential for debris, but the homeowner will not be able to
view the sump and determine if it is functioning. Therefore, the addition
of an alarm is recommended to provide a warning to the homeowner prior
to the onset of other problems, such as upheaval or water intrusion into
the structure.
Discharge lines should have clean-outs to allow removal of obstructions
by use of a snake or by jetting. Because effectiveness of these systems is
largely unknown until problems occur, it is wise to also backwash the system from the discharge end
and/or at the sump at lease every 2 years. The effectiveness of this backwash will normally be seen by a
discharge of debris, which may have clogged the system.
Capillary drains are many times utilized as moisture barriers along the perimeter of a foundation to shed
water and stabilize sub slab moisture. This will include extension of an impermeable barrier drain material
under flower pipe beds and up along French Drain grade beams. Therefore, it is important for the home-
owner to avoid any planting action that may puncture the barrier material. If this damage occurs, it will be
necessary to patch the hole with materials that maintain the integrity of the barrier.
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Irrigation/Sprinkler Systems
Watering of lawns and house perimeters must be regulated to maintain consistent moisture content under
the foundation. Therefore, allowances for shrubs, plants and trees must be regulated for each segment of
the yard. It is advisable that watering along foundation perimeters should be on a maintenance basis in
corroboration with seasonal needs. This should be in conjunction with plant and tree requirements so that
added water will not be siphoned from under the foundation.
Seasonal monitoring will necessitate different watering for the
sides that receive added and hotter sunlight (south and west
sides), which increases evaporation. This monitoring will also
take into consideration time of day for watering. Most
authorities recommend early morning watering so that less
evaporation will occur.
It must be understood that over watering can be just as damaging
to the foundation as under watering. If an electronic sprinkler
system is installed, each of the factors listed above must be
incorporated into the sequence and timing. Visual observations
must also be included in the process to make adjustments
beyond the capacity of normal programming.
A variety of watering heads and systems are on the market that can be customized to a homeowner's
needs. There are bubble sprays, side sprays or angle sprays that discharge from riser heads or pop-ups and
can be mixed to provide complete coverage. Where evaporation is a concern, however, a drip system will
provide necessary watering very efficiently. A close inspection of the ground surface is necessary to
ensure appropriate volumes and consistency. The goal is to keep the soil near and under the foundation a
consistent moisture (neither wet and/or muddy nor dry and cracked).
An inspection of the sprinkler system should be performed at least twice a year to determine if zones are
functioning properly and if heads are improperly discharging/broken or if leaks have occurred that will
provide uneven watering. This will, in the case of electronic watering systems, require running through the
system to determine if times, duration and frequency have been maintained.
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Vegetation And Trees
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Studies from England and the United States have proven conclusively that trees can cause damage to
foundation stability and in more severe cases complete foundation failure. Engineering studies map the
effect of moisture withdrawal, which can severely damage a slab- on-grade foundation and cause
movement in a pier and beam foundation system." Even when the perimeter of slab has been underpinned,
the interior slab will often deform as moisture migrates to the perimeter as a result of root capillary action.
Planting of shrubs, flowers and trees should be with the understanding of mature growth. Since additional
moisture withdrawal will occur, distance and watering patterns must be planned. If distance away from the
foundation cannot be maintained, root barriers may be necessary to reduce and/or eliminate penetration
under the slab and subsequent moisture withdrawal during times of drought. The depth of this barrier may
vary according to tree or plant root expectations. These barriers, if properly constructed, can also serve as
a moisture barrier, which will add stability to moisture contents under the foundation. Several agriculture
agencies have material available which provides projected root and moisture requirements for different
types of vegetation.
Trees should not be planted closer to the foundation than approximately the mature height of the tree.
Some studies also indicate the tree limbs should not invade the footprint of the house at maturity. There is
a variance with different types of trees that will necessitate their planting even further away. If the proper
distance cannot be maintained, it may be necessary to install a root barrier to reduce the risk of future
problems. Pruning of tree branches so that they do not extend over the structure .can . also be an effective
way to limit root growth under the foundation.
The plants should fit the environment. In areas where droughts frequently occur, it may be necessary to
substitute drought resistant plants and trees to incur less action on the foundation and provide easier
maintenance of the foliage.
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Plumbing Leaks
Leaks in water and sewer lines will change the soil equilibrium under a foundation and can lead to
differential movement/damage. Therefore, it is necessary to recognize signs that indicate problems exist.
If sewer lines are frequently stopped-up and roots are observed when clean-out rooters are used, a sewer
test should be conducted to determine the presence and location of the break. Repair of a break should be
made immediately to avoid damage and future problems.
If abnormal- water bills indicate a sudden surge in water usage, wet spots occur that can- not be explained
or the owner should hear the sound of water running in a bathroom (note: The bathroom nearest the water
supply line will provide the best indication of a water leak), a test of the pressure lines should be
conducted. If leaks are found, they should be repaired immediately.
If hot spots occur in the floor or unexplained water should pool, it is a good idea to call a plumber.
Catching leaks early will many times avoid extensive foundation damage that may be very difficult to
repair.
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Plumbing Leak Repairs
Leaks will often occur under a slab-on-grade foundation that require breakout of a segment of the slab to
gain entry and repair the plumbing. Care should be taken to perform proper compaction of the soil when
repairs have been completed. This will require adequate moisture in the utilized soil and compaction of
layers no thicker than 3" to restore soil bearing to as it existed prior to excavation. The vapor barrier
should be repaired with plastic and a bonding material to provide a vertical moisture stop from vertical
capillary action or water migration that may enter the living space.
Even in the case of post tensioned slabs, a minimum of #3 reinforcing steel bars, at a spacing of 12" on
center, should be utilized by drilling into the existing slab horizontally and epoxying the reinforcing steel
bars to provide integrity. A bonding agent should be utilized at the edges to provide the necessary bonded
joint between existing and newly placed concrete. It is normally advisable to install a moisture shield at
the surface to prevent migration of water through the concrete. This same procedure should be employed
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if it was necessary to break through a grade beam to repair a plumbing line except that non-shrink grout or
epoxy concrete should be used to remold the beam.
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Reinforcing Steel Exposure
Many times concrete will blister or peel along the grade beam and reveal post tensioning cable ends or
conventional reinforcing steel bars. If left unprotected, corrosion will slowly reduce the originally
intended strength of these reinforcing steel members. Therefore, it may be necessary to properly clean the
steel and remove all bond and then install an epoxy grout or non-shrink grout to build back the beam and
protect reinforcement. In more severe situations, it may be necessary to drill and epoxy reinforcement
dowels/ stirrups to build out the grade beam and provide adequate coverage of the reinforcing steel.
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Brick, Rock Or Cladding Cracks
Movement, weathering and freeze damage will often times create cracking in the brick veneer or mortar
that will allow passage of moisture into the vulnerable wall material. Because this will often lead to
deterioration of wood members, it is advisable to seal these cracks with a urethane, mortar or caulk that
will prohibit weathering problems. Where obvious structural problems are visible such a lateral
displacement of veneer, lateral shields or other retainers will be required to prevent additional movement
damage.
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Vent Covers
The original purpose of vent covers is to provide adequate circulation of air under the floor of a pier and
beam foundation so that moisture will not build up and cause deterioration of wood members. Although
coverage of these vents will save money in reducing heating bills, it will often provide the unwanted
environment for wood rot. Therefore, it is not advised that these covers be utilized unless other means of
air circulation are available such as a sub floor vent fan(s).
Recent revelations of houses where the growth of bacteria was so invasive and so deadly that the houses
could not be salvaged, have led to anew examination of detection and prevention of such growth.
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Animal Damage
Dogs, skunks, armadillos, snakes etc. will many times burrow under a slab or pier and beam foundation.
This will undermine the bearing soil and may provide entry for water that was not possible prior to the
excavation. Therefore, it is necessary to back fill the segment and/or place an impenetrable shield to
prevent further entry. It is also important to restore positive drainage to prevent foundation moisture
instability.
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Termite Damage
Wood should not touch the ground at any place near a foundation. This will only invite termites and
provide avenues for their passage to more appetizing segments of the structure. Therefore, the homeowner
should take care to avoid laying, placing or constructing wood that engages the ground. This includes
removal of any wood pieces that may exist in the crawl space of a pier and beam foundation. When you
add moisture to wood on the ground, you provide a perfect environment for growth of termites and other
wood eating insects.
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Interior Doors
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It is a known fact that most slab-on-grade foundations will move
differentially, which can cause misalignment of interior doors. Therefore,
some flexibility in the fit of the doors will reduce the inconvenience of
this movement.
Interior doors should have a minimum 1/8" to 3/16" clearance between
the top and side with the frame. This will allow some seasonal movement
prior to sticking. It is also a good idea to provide adequate clearance off
the carpet or floor to further buffer movement and allow for different
heights of carpet and/or flooring.
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Home > Forums > Civil / Environmental Engineers > Activities > Earthwork/grading engineering Forum
French Drainsthread158-162089
beryl10 (Chemical) 8
Aug
06
22:52
Hi,
I have a couple questions about french drains. Our property slopes from the street down towards the house and the house sits quite
low in the gound, so, not surprisingly, water has always been an issue. We're putting in some french drains in the front of the house to
intercept the water and move it off to drain pipes running out the back to a stream. These are being placed about 4 feet away from the
foundation. I'm happy with this placement. I think it makes sense.
However, in another area, around the corner on this L-shaped ranch, the contractor is suggesting putting the drains right up next to
the foundation of the house. The house has a basement, and I am not talking about drains at the floor of the basement, but at the level
of the ground outside. I am wondering if this is a good idea. Isn't the french drain actually drawing water towards it, therefore pulling
more water towards the house foundation if there is a 2' deep x 2' wide trench filled w/ gravel right up to it? Maybe all is fine if the
drain works properly, but from what I understand, french drains are not the longest lived drain. They do clog up over time.
Next question, he also said that putting geotextile fabric on top of the drain slows down the percolation of water from the top. So, he
just cut the fabric right off to the surface, which I don't think was very smart. I'd like to landscape right up to the edge of this trench
(make the trench look like a gravel path with stepping stones), and now there's nothing keeping the soil from spilling right in. He just
wants to dump river stone on top w/o the fabric barrier. Any thoughts on not completely wrapping these drains? Our soil tends to be
on the clayey side, but this drain also abuts quite a bit of amended soil (more loamy and organic)
thanks in advance for comments, expertise, etc.
LHA (Civil/Environme) 9
Aug
06
8:10
You are correct on both concerns.
Never put a french drain against a foundation with a basement. However, along the footings is OK, if you put some 3" dia perforated
flexible HDPE, with a filter sock over it. This site will have several products:
http://www.ads-pipe.com/en/index.asp
Can't you grade away from the wall? Even the 4 feet you mentioned in the front is very close. If you can only get several inches of
fall, over about 6-8 feet will help.
Always completely wrap the clean stone in the trench, and overlap a foot or more...for exactly the reason you've mentioned.
Engineering is the practice of the art of science - Steve
cvg (Civil/Environme) 9
Aug
06
12:04
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your contractor is partially correct - the fabric could slow down percolation, especially if specified incorrectly. It would need to be
specified with sufficient hydraulic conductivity to pass the water. In addition, the fabric is designed to prevent the fine soil particles
from contaminating the gravel. By doing that, eventually the fabric could get clogged with silt. Perhaps a better option is to provide
a granualar sand and gravel mixture which will provide a natural filter to your local soil. This can be rejuvenated from time to time
by scraping off the accumulated soil from the surface. If not, you may need to perform the same type of maintenance on your filter
fabric.
Regarding the distance from the foundation, sloping the ground away from the foundation is recommended. A small swale should be
graded over the top of the french drain to allow the water to collect and percolate properly. Recommend at least 2% slope or greater
away from your foundation. With only 4', this provides less than 1 inch of depth in your swale. Would be better if this was 2 or 3
inches.
oldestguy (Geotechnical) 9
Aug
06
21:54
The message you are getting is that you need to filter any water going into a pipe, single size gravel or other drain system. If you
don't use a filter, they will plug up and the whole thing will fail. I've seen gravel backfilled perforated "tile" plug up in one year.
For many years now (since the '30's Corps of Engineers study) it has been known that one of the best filter backfill materials to any
drain is ASTM C-33 fine aggregate for concrete, known as "concrete sand". If your drain pipe has slots in it, you don'teven need to
put a sock on it with this backfll.
I definitely would not set up the situation for surface water to enter the trench backfill, as with a "gravel path". Isn't there any way to
divert this water away, even if you have to install an inlet or two and a separate "storm drain" system?
A clay layer on top of these drain (filtered) systems can be used to keep the surface water out.
However, if you are careful this system described below works well: You may even find a landscaper that has done it. I have never
seen one that knew of this before I taught him.
You mix into the top 2 to 3 inches of soil (any kind) two pounds per square foot of powdered (not granulated) bentonite. It is known
as "driller's mud", avaliable at plumbing supply houses. A roto-tiller works good for this. Don't use an excessive amount or this
"water loving" material will swell and turn the place to grease. The principle here is that this amterial takes on some water and swells
and fills the soil voids. A little does a lot of sealing. It is a natural volcanic clay.
To be effective, this procedure has to treat the whole area of house backfill, not just a few feet out. In most cases, you first strip the
sod off all that backfill. Later roll the sod back and that lawn will stay quite green. Bushes can be left, but work closely around
them.
If you wish, work the worst areas first and see how it works.
Of course you also do all that you can to shed off that surface water anyhow. Don't intentionally try to have surface water soak into
some form of gravel drain. You will regret it.
In summary, protect the ground from water entering, but once it gets in, use a filtered drain system to remove it.
If you find you are getting water in the filtered drain system all year, that outlet should be under the water at the discharge area or it
will freeze and then nothing works.
I've preached this "serman" maybe a hundred times and still find that gravel seems to be in the minds of people as the required
backfill to drains. However, the first underdrain I had installed was in 1954 as a grad student studying them under highways and last
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time I visited there it still works. I have never found a failure of sub-drains that have been backfilled with concrete sand in all my
working life.
If I was writing the specs for this job I would say "No Gravel Allowed on the Job". The idea seems good (good percolation), but it is
not a filter and it is difficult to keep it protected. You can't goof up the job using concrete sand.
beryl10 (Chemical) 12
Aug
06
11:36
Thanks for the replies.
We are fairly limited in how much we can grade away from the wall since there are some big trees about 10 - 12’ in front of the
house, and getting too close to them would cause a lot of root damage. We had already created a bit of a swale about 5 feet in front of
the house, and picked that for the location where the pipe was installed. The ditch was dug out 2 feet wide, so the trench begins 4’
from the wall.
I dug out the gravel enough to put in new pieces of filter fabric along the sides so I can wrap the top. In looking at the dimensions of
this trench, I was wondering how this really works. It seems to me the trench would have to fill up with quite a lot of water before it
could even enter the pipe. To be exact, it would have to fill with at least 127 gallons of water before the level is at the pipe (25’ long
x 2’ wide x 4” of gravel between the bottom of the pipe and the bottom of trench). So, isn't a french drain just creating a big basin for
water to collect, only 4 feet from the basement wall foundation, and that the water would probably seep into the soil faster than it
would ever build up to find its way into the pipe, except perhaps during a very big rain. But, then mightn’t a surface drain be more
effective? The direct area of lawn between the house and the street is about 1300 sq. ft., which could, during a 100yr rainfall,
produce 14 gal./min. runoff (based on 3”/hour, and grass surface runoff coefficent of.35), so, yes, it would fill to the height of the
pipe in that situation. I guess my question is this. What happens to all the water that doesn’t make it up into the pipe? Would it be
better to sit the pipe closer to the bottom of the trench? Most diagrams I see of french drains do set the pipes on about 2-4" of gravel.
Or, wouldn't a narrower trench be better. Again, I see alot of them are 2' wide, but if it were only 12" or even just 8", then the water
level would reach the pipe much less water in there.
On paper, the idea of a French drain was great. But, as I look at it now, trench dug out, I do question whether or not this is the
solution. My initial thought on the French drain in this location is that it would act as a curtain or interceptor drain. However, I was
just reading on the NDS website that a French drain can provide this function only if the downhill side is lined with a polyethylene
film.
I have a question to oldestguy: Why don’t I want surface water to enter the gravel trench? I thought with gravel brought up to the
surface, french drains can support the function of removing both subsurface and surface water.
Also, does anyone have any thoughts on some of the prefabricated composite drain systems?
Thanks again to everyone.
oldestguy (Geotechnical) 12
Aug
06
12:58
My intent in my first comment was to get you to change the whole system to collect surface water, separately from ground water.
Also, you may see that I recommended two things more: Seal the ground surface and install a subdrain.
However, let's look at what you have and see if that can be fixed.
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The term "French drain" in my view is an old fashoned way to collect ground water and divert it from an area, such as an orchard or
farm area in low ground. It is not a filter and in time can plug up. It is not a system for collecting surface water specifically.
What you have built is not such a ground water collector. It appears to be a collector of surface water and designed so that the water
collected also can soak into the ground and then affect your basement. I suspect your "contractor" is some sort of impractical
dreamer, certainly not using common sense.
My recommendation is that you get rid of the "contractor" and get someone on the job with common sense, if you need help, to
correct things.
Since you have a trench filled with gravel, you might change this to a surface collector only and perhaps that would do the job. But I
doubt it. If you want to stick with the trench OK, but it would not be as permanent as if you had a shallow "ditch" or swale, lined or
made water proof, possibly with the bentonite treatment of earth. Any place you have water in contact with earth is a place for water
to infiltrate. House backfill is usually loose and water easily enters.
Sticking with the current trench:
To make this a surface water collector, this needs to be a waterproof container. Lining it, sides and bottom, with plastic is a thought,
but I have never seen plastic to be totally waterproof, unless you seal all the seams. Concrete is better, but not perfect either.
Sealing the lining to a drain pipe also is needed and that drain pipe should be at the lowest elevation in the trench, and sloped down
from there. The pipe should be solid walls, not slotted.
If it was me, I'd bite the bullet and do this minimum step: But think about the affect of later doing the sub-drain as if affects this
work.
Dig out the gravel and fill the trench with earth, preferably silty clay or a bentonite treated sand. Compact it if you can.
Waterproof the whole house backfill area at least on the uphill side with the bentonite treatment and slope everything to the filled
trench area, which is then shaped like a swale and sloped to inlets. This is a surface water collector only.
These inlets can be purchased at plumbing houses and sealed to plastic pipe to carry off the water.
Lacking the inlets and drain pipe, continue the swale around the house and off from the house area.
If you really want to use "suspenders and belt", you first dig down alongside the upper foundation walls and install the slotted plastic
sub-drain that is totally separate from the surface drain work. Use the concrete sand as the backfill up at least a few feet above the
basement floor. The slotted pipe should be a low as possible, along side the footing if possible. Give it some slope if possible, but
not mandatory. Use excavated soil for the remaining backfill.
Then do the surface waterproofing and swale as described above.
With what you now have I think you will see more water in the house than before. I am sorry I did not explain this before, and, I
probably did not clearly explain that it is the wrong thing to do, in my opinion.
You should know that I have fixed many a site such as yours and that it is not always possible to stop all seepage. Sometimes water
enters the house backfill far from where it then gets into the basement. Therefore you usually have to work in steps, get the most
obvious done first and observe.
beryl10 (Chemical) 12
Aug
06
16:58
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Thanks for the response. You were clear the first time, but that drain was already in. And, the contractor already fired. Though, that
was due to other sloppy work. If I were doing this project again, I would first hire an engineer to design the plan, and not just hire the
guy who calls himself a drainage contractor. Live and learn.
After the whirlwind of activity around here, and several problems with the contractor, I starting thinking more and more about this
design. Though I initially thought a french drain in front of the house to collect and remove surface and subsuface water flowing
towards the house made perfect sense, I later starting seeing flaws with this as a solution. However, I've read about french drains
being used in this manner - wrapping the house on the uphill side, a few feet away from it, and I initially thought it seemed logical.
Anyway, what I'm now thinking I could easily do is to just dig out the gravel, and replace the slotted pipe with a solid pipe and
connect several catch basins along the length. This pipe would be 5' from the house (b/c thats where the slotted pipe is and the
connection to the drainpipe going back to the stream), and the catch basins would sit in a bit of a swale.
Any comments on this idea are welcome.
thanks.
oldestguy (Geotechnical) 13
Aug
06
12:31
OK a good explanation.
Well, as I uderstand it, the sides and bottom of this filled trench still are in contact with the soil and not sealed, as with a plastic
sheet. Thus, before the water is in the pipe and flowing away, it has the chance to infiltrate soil backfill to house and affect the
basement. Usually backfll was shoved in with sloping "layers", that promote the ability of the water to seep toward the basement.
So, If you are going to replace the pipe anyhow, why not at least seal the bottom and sides of the tremch.
If gravel is to be used again and some inlets are to be installed, I am assuming you will have them in the base of the trench, right?
In that way you may not be able to correct possible plugging of the gravel with sllt in time.
I know it is more work, but why not forget about this trench thing and fill it with soil, placing your inlets where you can see
them? You still can use the trench for the discharge line.
And if you wish to waterproof the ground surface with the bentonite treatment, it will tie in more easily with your surface water
collection system.
The gravel thing is likely to be a maintenance head ache for years to come.
If you gave thought to use a bentonite treatment of the gravel for salvaging it, yet making it water tight, I think that will take some
experimenting with varying precentage of bentonite, soak it and see what happens. This can be done in a 5 gallon bucket with
bottom perorated. Too much bentonite and swelling may amaze you.
geosavvy (Geotechnical) 22
Aug
06
16:49
Bentonite is nasty stuff. Make sure you get your blend right before you spread it willy nilly.
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Also, I personally would recommend against using any type of soil filter material. The gradation of the filter material has to be
customized for the type of material you are filtering, else the particle arching required to filter will not happen. Its easier to go with
the local tried and true geosynthetic fabric that works for the soils in your geologic area.
beryl10 (Chemical) 23
Aug
06
12:05
Sorry, this is kinda long, but I'm just trying to understand a couple things.
It seems as though a lot of people on this forum aren’t so in favor of using a shallow French drain to collect, move and divert water
from running towards a house where the property slopes towards it, yet, a lot of other people (landscapers, drainage parts stores,
gardening forums) seem to think they’re great. I am no longer very convinced that they are a good solution to what is probably
mostly a surface water issue, however, I’ve become obsessed with thinking about how water moves through the landscape, and soil,
so, I have a couple questions.
1. If the coefficient of runoff for grass is .35, I assume that means that 35% of the rainfall flows over the surface and 65%
percolates into the soil. So, where does that 65% of the water go once it percolates into the soil? Does it move horizontally below the
surface until it finds its way to the bottom of the hill? Or is that majority of that 65% of the water getting used by the grass, trees and
other vegetation before it has a chance to move down slope?
2. Why doesn’t the calculation for runoff take into consideration slope? I assume that slope must make a big difference, and on a
steep grassed slope, more water is runoff than on a shallow slope where it has more time to percolate into the soil.
3. If a French drain (not lined with anything impermeable) daylights (to collect surface runoff in addition to subsurface water), how
much of the total water actually makes its way into the slotted pipe versus percolating through the ground at the bottom? In a slow
but steady rain, could the water actually penetrate the soil beneath the pipe faster than it builds up to a level high enough to enter the
holes on the bottom of the pipe? I guess many factors affect this, including how saturated the soil is to begin with, the permeability of
the soil, and even the dimensions of the French drain trench (width and depth below the pipe determines how much water must fill
before it reaches the bottom of the pipe).
4. What system would collect more water? A series of surface drains or the French drain with gravel to the surface?
Here's my thinking on this:
If we can assume a surface drain collects 100% of surface runoff, which is 35% of total rainfall on this grass covered sloping surface,
then 35% of the rainfall will be removed by the surface drains.
If the French drain trench captures 100% of the surface runoff (35%) + some fraction of subsurface water (the 65%), LESS the
amount that percolates into the soil below the pipe, what total percent is entering the drainpipe?
Of course, I have no idea what percent of the subsurface water it will capture, and what the loss from percolation below will be. But,
if the fraction of subsurface water that enters the trench is much larger than the total loss to percolation below the trench, then a
French drain is the better system. But, if the percolation into the soil is high, and/or the amount of subsurface water entering very
low, then surface drains are the better solution.
I don’t suppose there’s any rule of thumb for this, is there?
Am I over thinking this?
The trench is already there and I can finish it off as a french drain, or put in solid pipe with a few catch basins and inlets. I don't feel
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like experimenting with the bentonite or other methods of making the trench impermeable. If percolation is a big issue, esp. 4 ft. from
the basement wall, I'd go with the solid pipe and inlets.
cvg (Civil/Environme) 23
Aug
06
12:41
to answer some of your questions -
Percolating water generally moves vertically downward unless there is some driving force such as daylight, an embankment or
impermeable layer that forces it to move horizontal. Once it leaves the french drain trench, it may not daylight.
The rate of water use by plants is slow and doesn't have a very large effect on the amount of storm runoff or soil percolation. The
65% is retained, soaks in, evaporates and some is transpirated by plants - but does not run off.
Runoff calculation does consider slope – it is a function of the time of concentration. For higher slopes or smoother surfaces, runoff
velocity is higher and the time of concentration is smaller - consequently, the peak runoff is higher
Water will seek the path of least resistance – if a smooth pipe is there it will flow through the pipe much faster than it percolates into
the ground. This is one reason to provide a pipe in a french drain (assuming the purpose of the french drain is for removing water
rather than for allowing the water to soak into the ground)
What system would collect more water? Depends on the design, but surface drain is probably more efficient at removing stormwater,
if the stormwater can be directed to the drain before it soaks into the ground…
beryl10 (Chemical) 23
Aug
06
13:01
But, if the french drain pipe is on 4" of gravel above the bottom of the trench, doesn't the trench have to fill up with 4" (actually 5"
since the holes are a little off the bottom) of water before it gets to the pipe? At the dimensions of the current trench (28" wide x 25
ft. long) it would fill in with 127+ gallons of water before reaching the pipe. A big storm would of course fill it at 14GPM which
would reach the pipe quickly, but for the smaller rainfall amounts (lets say, 1GPM over the course of a day) it might never fill it
enough to reach the pipe, right? then could percolation exceed the rate at which it fills?
i guess this is my fear. that we're putting more water into ground close to the foundation than w/o the trench.
cvg (Civil/Environme) 23
Aug
06
13:20
some water will percolate down, hit the pipe and run into a hole without ever reaching the bottom of the trench. Also, you are vastly
overestimating the amount of water necessary to fill your french drain trench. It is filled with gravel or sand which occupies most of
the space. Water only fills the volume between the grains of sand. I would guess closer to 20 or 30 gallons of water maximum to fill
the bottom 4 inches.
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However, as recommended by oldestguy - to remove surface water, I would stick with a surface channel and grated inlets into your
(non-perforated) pipe. If you are trying to lower water table next to the house, then use the french drain with the perforated pipe.
beryl10 (Chemical) 23
Aug
06
13:22
ah, yes, I totally forgot about all the space taken up by the gravel.
thanks.
beryl10 (Chemical) 23
Aug
06
16:27
How does one determine where the water table is? I assume to lower the water table, the french drain has to be very deep.
beryl10 (Chemical) 23
Aug
06
16:38
I don't know if any of you are familiar with the "Ask the Builder" website. Here he explains water movement through soil and using
the french drain to protect ones foundation.
"When it rains, water enters soil and pushes the air to the surface. Gravity then takes over. If your yard slopes, the water within the
soil actually begins to flow downhill."
"A linear french drain is simply a "moat" that protects your yard or house from sub-surface or surface water. You construct it by
digging a 6 inch wide trench approximately 24 inches deep. .... If your intent is to protect your house from water, you construct the
trench approximately 4-6 feet away from the foundation. In many cases the trench system is U shaped as it passes around your
house."
He extends the gravel to the surface to collect surface water.
http://www.askthebuilder.com/175_Drying_Soggy_Soil_-_A_Simple_Trench_Drain.shtml
All the explanations I've gotten through this forum make alot of sense, but then so does Ask-the-Builder, to some extent.
cvg (Civil/Environme) 23
Aug
06
17:49
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percolation is driven by gravity and as such, the only way it can "flow downhill" is if there is something blocking it from going
straight down such as a layer of rock or clay or an easier path to follow such as through a pipe, through a crack etc.
"Bob the builder" has a degree in geology, but apparently according to his profile on the website, has earned his living flipping
houses and never practiced engineering.
oldestguy (Geotechnical) 24
Aug
06
21:22
Hi again:
I think too much time and worry is being done about quantities and rates of water flow. Heck, storms are all different and that once
in 10 year thing may be carried OK by the job built, but the once in 20 or more years won't. Intensity of each rainfall also is
different.
So you really probably are not in a position to worry about which your system will take. You just build it as big as practical and take
simple other precatuions so that any standing water won't run into window wells and other places of concern.
I take exception to a few statemsnts made above. The best all around filter for subdrains is concrete sand, for all soils. You don't
need to worry about gradations of those materials either. Where there may theoretically be fine clays that theoretically will pass thru
the voids of the concrete sand, well don't worry. The cohesion of that clay material keeps it in position pretty well. THAT CLAY
IS UNLIKELUY TO SEEP ANY WATER ANYHOW. It is the sand seams that do the seepihg and they are held back by the
concrete sand.
Another thing about concrete sand. It is darn difficult to foul up the the job. On too many jobs, asking for complicated procedures is
asking too much of the usual contractor doing small jobs. Then too you get the guy that has been using questionable practices (such
as using gravel around sub-drains), of recommending these "french drains" and he "knows better" and keeps doing it the same old
dumb way.
Also, water seeping into basement backfill will follow the the path of least resistance and it usually is not straight down. It usually is
slanted towards the wall, due to the usual way this backfilling is done. Thus water soaking in 4 feet from the basement wall will flow
towards the wall on that slope.
Take to heart my philosophy about construction:
IF SOMETHING CAN GO WRONG ON CONSTRUCTION, IT WILL GO WRONG.
beryl10 (Chemical) 24
Aug
06
23:21
Yes, I probably have been over calculating, but was just trying to quantitatively understand how well a French drain removes water,
and where the water is coming from. When we talk about subsurface water, does one mean 1 foot down, or 5 or 10? With a ditch
only 1.5 feet deep, how much subsurface water would a French drain even intercept? These questions are what led me down the
quantitative road wondering, would this French drain put more surface water into the ground than the amount of subsurface water it
removes?
So, anyway, I am going to install a solid pipe w/ 5 inlets (catch basins) along the 25’ length, and backfill with soil. Forget about this
whole gravel pit. I hope this will prove to be the right decision, as moving tons of gravel is no small chore, and now I’m stuck with a
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pile of gravel (guess I can use it for a foundation for that garden shed I’ve been wanting to put up).
Why do you think everyone backfills with gravel, when concrete sand is superior?
Does the backfill against a basement foundation really go out 4 feet away from it?
Even though I’ve abandoned the French drain, I was wondering whether clogging really such a big an issue with the stiff HDPE pipe
that has 2 rows of fairly large holes along the bottom compared with the corrugated pipe with slit type holes all the way around? Do
roots tend to go into these holes? I was amazed how many fine roots have already grown through the geotextile fabric, though
wondered if they would continue on through the gravel to find their way into those holes. It seems it would be difficult to plug them
up with silts.
blueoak (Civil/Environme) 24
Aug
06
23:59
Sorry oldestguy, but I disagree with your filter statement. I think for residential and other little jobs spec'ing concrete sand is fine and
your advice for this job is excellent.
But if you need a filter on an important structure you need to do the work on designing a filter. I home isn't that big a deal to the
neighbors, but a dike or dam with fines migrating downstream is a little more important. Concrete sand isn't always applicable and
what about filter design below riprap or gabions.
beryl10 (Chemical) 25
Aug
06
12:17
I'm rereading this whole thread and see that I asked before why one wouldn't want surface runoff going into a french drain, but I
realize I still don't quite understand why. Is the simple answer that not enough of it gets transported away in the slotted pipe? I
understand not feeding a gutter leader directly into the slotted pipe, but why not the runoff from the surrounding lawn into the gravel
trench with the slotted pipe?
I'm still questioning this b/c this will be alot of work to change, and wonder if its all that bad to leave it as a french drain.
cvg (Civil/Environme) 25
Aug
06
13:06
french drains are ideal for intercepting and draining subsurface water. However, surface drainage is most efficiently removed using
surface drainage methods such as a swale or grated inlets into a pipe. Intercepting surface drainage with a french drain will increase
the amount of water that infiltrates into the ground at that location. You never said that you had water coming into the basement
through the foundation walls, however, by putting a french drain near your foundation and allowing it to also intercept surface water,
you could possibly create another problem rather than solve one.
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beryl10 (Chemical) 25
Aug
06
13:25
thank you. That was the direct, to-the-point kind of reply I needed to hear. Really, it was my question that needed to be more direct.
With all my convoluted calculating I didn't ask the direct question.
Anyway, no, there is no water coming into the basement through walls. That was taken care of ages ago with, I guess, perimeter
drains (french drains?) in the basement leading to 2 sump pumps. That was before my time. As long as the pumps work, all is well,
although damp.
BigH (Geotechnical) 26
Aug
06
5:42
blueoak - see Terzaghi Peck and Mesri. Oldest guy is correct that for any fine grained soil, the use of concrete sand is "fine". This
was first told to me by Charles Ripley of the old Ripley Klohn Leonoff of Vancouver - and one of the pricipal sources for that given
in TP&M. For coarser soils, you will design the filter - but remember that a lot of work has been done over the years with respect to
the original equations and filter criteria. I suggest too that interested members read the few pages in Conduto's book on Soil
Mechanics and they will see a good summary of "filter" criteria for finer grained soils. This is also give in one of the US military
manuals.
With respect to cvg, if the soil in which the french drain is placed is clayey or low permeability soil and the material in the french
drain is sufficiently permeable, I doubt any of the water will enter a pipe anyway and he suggests but apparently - cvg must be
assuming that the holes are pointed up when he indicated that 'some' water would enter the holes - although it is more conventional
and in line with AASTHO recommendations to place the holes downward. A pipe, in my view, is really only necessary if you have a
large volume flow of water - or, since the pipe is not very expensive you put it in for redundancy. Very few early-on french drains
ever used pipes. I would put them in only if I believe that it is necessary to do so in order to ensure tha the french drain doesn't build
up an appreciable head of water.
BigH (Geotechnical) 26
Aug
06
5:45
oops - " . . . as he suggests . . .", not " . . . and he suggests . . ."
beryl10 (Chemical) 26
Aug
06
9:14
BigH - The french drain was built with a pipe, holes facing down, connecting to a solid pipe that the gutter leaders and sump pump
tie into and runs out to a stream at the back of the property. The french drain is only in the front of the house. It has gravel surfacing
to the top. No soil on top. Is meant to intercept surface water running down the sloped lawn in addition to subsurface water. So, why
do you say the water wouldn't enter the pipe? Or do you mean that subsurface water doesn't seep out of clay soil very well?
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oldestguy (Geotechnical) 26
Aug
06
13:38
Hi All:
A fun topic, and I trust all is pretty well resolved at the house in question.
Now for blueoak and the "disagreement". Really there is no disagreement, since I refer to "subdrains" as being most suitably
backfilled with concrete sand. Let's define "subdrain". My use of that term "subdrains" started in 1954 (when I did my Master's
thesis on highway subdrainage at Cornell). The term comes from what Armco Steel put out years ago in their "Soils Manual', or
similar name. A subdrain,in my terminology, is mainly used for draining ground water. It is not generally a term used for toe
drains at earth dams or other important structures where the drainage is not generally taking ground water, but rather seepage water in
large quantities, etc. Yes, using the accepted ratios for filter design is a good idea for these jobs. But, for highway roadway frost
heave areas, base course drainage, house basements, etc. it generally is the case that designing a filter is not practical and usually not
needed.
Then comes what about the pipe and holes? Armco's original "wrinkled" corrugated steel subdrain pipe had its holes on the
underside at the quarter points, 3/16" diameter. Under heavy flow of water some of the finer grains got in, but soon the coarser
grains bridged over those holes.
For the more recent wrinkled plastic pipe with slots, maybe 1/16" wide, some sand also gets in and a bridging over then takes place
also. I have heard complaints by state code folks that they have seen the fabric sock on these pipes clog over at the slots, but I have
not seen this happen. Maybe these cases were backfilled with gravel? None of the installations I have been involved with used the
sock and they all seem to function fine. Since no excess sand gets into the pipes causing problems, we also no longer ask for
clean-outs to be installed, just in case.
The reason I am so against any gravel on the job is that we once called for using gravel directly around the pipe, with concrete sand
under, beside and over this gravel, something one would design with the filter ratios. A difficult thing to do, but it looks nice on a
drawing, to satisfy the architect who likes the term gravel for some reason.
Well I stopped by the school job where this was to be done and there the skid loader had dumped load after load of gravel over the
pipe two and three feet high, totally in "violation" of the nice looking drawing. After that, all gravel was removed from drawings and
the dumping of concrete sand was the case, and that has worked fine. As I have said before, it is difficult to goof up the job when
only concrete sand is the backfill, (at least around the pipe) .
BigH (Geotechnical) 27
Aug
06
9:45
beryl10 - it was more a general statement. The critical point in french drains is that the drain drains somewhere and the permeability
is sufficiently high (usual greater than 1 cm/sec) that water passes out quickly. Optimally, your french drain is connected by gravity
to an outlet. You may need some significant volume flow in order to fill up the drain rock below the pipe in order for the water to go
into the pipe. If you have the flow, the pipe will drain water; if you don't, the pipe will remain dry and the water will be passed by the
drainrock beneath the pipe. Now if your french drain is not connected in a positive fashion and you are relying only on the pipe to
drain water, then it really isn't a french drain but more like a "storage" pit.
blueoak (Civil/Environme) 31
Aug
06
14:09
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13 of 16 24/03/2007 9:10 AM
Oldestguy,
Thanks for the definition and correction. I have been stuck with embankments lately and am a little shortsighted.
BigH,
As always good references. I am a little worried though that "concrete sand" can mean too many things. I have seen "concrete sand"
tested that didn't meet filter requirements on a clay dam.
BigH (Geotechnical) 3
Sep
06
3:30
blueoak - you are correct in that the concrete sand may not meet the filter requirements against the clay in a dam - but one must
remember the underlying assumptions under which the filter criteria were based; and it is my recollection that the filter criteria were
developed with coarse grained soils in mind (sand, gravel) not with clay to sand. Clay's biggest problem in dams is with its
propensity towards dispersion and that is why they have developed the pin-hole test back in the early 70s. Concrete sand basically
means normal well graded coarse medium to fine sand in my view. Again, see Conduto, see Terzaghi Peck and Mesri - and, if my
memory serves me right, Milligan in one of the recent Terzaghi lectures (2002 to 2004) discusses this in his paper.
As well the infamous filter criteria, many love to use Hazen's Rule for the determination of "permeability" although one will have
problems whether to use 100 or 150 as the coefficient. But, the Hazaen's rule was developed for medium grained single sized sand -
yet, most texts do not point this out and engineer's over the years have used it irrespective of its assumption.
oldestguy - 1954, eh? Were you there when Cornell beat Ohio State two years running in football? Do you realize that Cornell
holds a 2-0 record agains that Big 10 powerhouse???
oldestguy (Geotechnical) 3 Sep
06
10:58
Big H
Nice to see another Cornellian. Can't recall. Undergrad time was '46 -51 (5 year course) then the 3 years in navy (you remember
NROTC?) before grad school there.. In undergrad days I was too poor, so I was an usher at the games. I only recall Army beating
the Big Red about '47.
That job was at Judd Falls road, near campus.
newoldguy (Geotechnical) 11
Sep
06
11:00
Some great information here.....Please help with a couple of questions... I am planning a curtain drain to be placed
about four feet out from the foundation of a house with a damp basement. I am planning to go down six to seven feet
and I like the discussions about concrete sand with drain pipe.Does the sand need to be "washed sand"? Any warnings about going
that deep with a "sand only" backfill?
oldestguy (Geotechnical) 11
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14 of 16 24/03/2007 9:10 AM
Sep
06
15:52
OK to the Newoldguy: The concrete sand I refer to meets ASTM spec C-33 for fine aggregate. It very likely is washed to get to that
gradation. In this neck of the woods they call it "Torpedo Sand" for some reason.
The obvious thing you want to do is cut off the flow towards the wall. I don't like the idea of anyone in a trench that deep unless it is
sheeted and braced. With no one entering the trench, this works most times. You follow the back-hoe excavator and immediatelty
roll in the 4" corrugated slotted plastic pipe and immediately dump some concrete sand on it. With that you then are 90 percent
done. For cost saving you might then follow with a local bank run sand up to near the surface where some impervious fill would top
it off. Should some cave-in occur, usually this method will still do the job. If you wish to try to compact the backfill, it depends on
your site. For some reason I don't recall having any later settlement problems on the jobs with no concerted compaction effort. Per
your question, I don't see where any "risk" comes in with sand backfill. The concrete sand does an amazing job without much
work. A little enters the slots, but then it stops due to bridging by coarser grains.
I'd not use this system for surface water drainage, as this thread is involved with.
With this method you may find the bottom of the trench and the pipe may not stay on a nice grade line. Therefore, going deeper to
allow wome wiggle room might be in order. The deeper the better for protecting the structure from water, but it might undermine the
footings.
You can see that doing it this way, it is difficult to goof it up.
Next is where to drain it to. On some jobs we install a man-hole and an electric sump pump, or run it to daylight down the hill. In
any case, if you are in cold climate, that outlet needs protection from freezing. An outlet under a lake is ideal. Your local codes may
allow it to go into the basement with a sump there and discharge to where they allow.
As an altrnative to the trenching some contractors will talk the owner into allowing a trench to be cut thru the floor next to the wall
and install a drain pipe there. It may work, but I've see these with water then seeping up out in the middle of the basement
floor. Perhaps the drain was not deep enough then.
jtc500 (Civil/Environme) 11
Sep
06
20:45
I have recently become part owner of a small rancher on a poorly drained site.I have decided to install a perimeter drainage system
and after much research conclude that concrete sand surrounding slotted plastic pipe (no socks) will be my choice method. It also
seems to me that if this system were to fail some time down the road that it would be a lot easier to dig out and replace than a system
involving sone or gravel.I also think I saw research many years ago claiming that uniform sand at 2mm would resist the passage of
termites.This foundation is only four courses high. In most areas except on the driveway side I think a 30" trench would be about
right dug to bottom of footing (angling slightly deeper going out)Probably will use one slotted 6" pipe but two or three 4" pipes
sound right also. Will tie into outside sump crock and try to pump to street.Cannot wait to start when I get some free time.I am 10
year bulder turned 25 year arborist-treeguy who would appreciate comments.
fattdad (Geotechnical) 11
Sep
06
21:37
I liked oldestguy's reply regarding the definition of subdrain. Regarding the use of crushed stone, washed sand or something
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15 of 16 24/03/2007 9:10 AM
in-between what's at issue is matching the grain size of the sand/gravel material to the slot size and the grain size of the water-bearing
formation. If I were at work right now, I'd give the basic guidlines, which relate to the D10 (or is it D20) and the D60 size. It's fairly
straighforward. That said, in this day and age, most just don't fuss with all this calculating 'cause there's filter fabric to rely on. In
some instances this can be false security.
Regarding the attraction of water to a subdrain from that basis avoiding the use against a below grade wall, I would not share that
concern. If you have positive drainage, it just would not be an issue.
fatt but-but-not-that-old-I-guess dad
oldestguy (Geotechnical) 13
Sep
06
20:12
ITC500 Nice to see you are planning a perimeter drain, doing something line a "buried moat around the building". The idea would
what I call a cut-off drain, cutting the flow toward the building. In my research I found it impractical to depend much on drawing
down the water table, by installing a low placed subdrain to hope the water will run to it. The main place you can hardly get away
from doing this is for agricultural drainage or athletic fields. For a football field I call for drains under the main yard markers, as
well as a perimeter drain. The aim is mainly to drain off rain water from in the soil, using the draw down effect. Not perfect, but it
works sufficient for play to go on.
So at a house, if possible, it also is a good idea to get some drains inside the building in case some water for some reason gets past
the outside drain. In sandy country these should be no farther apart than 15 feet, since most sands are not highly permeable and a
steady flow gradient of about 1 in 7 seems to be common.
Pipe size of 4 inch is plenty large enough for even the heaviest groundwater flow (usually). I do recall one 8 inch line flowing half
full for drainage of a road cut in gravelly sand.
jtc500 (Civil/Environme) 14
Sep
06
0:23
Thanks much oldestguy for your response.I am however dealing with a four block crawlspace with duct runs below making the
prospect of installing an interior drainage grid system scare me a bit.Of course down the road I might be forced on my belly to do just
that.It does occur to me also that since a dwelling routes the rain water outside the perimeter drain changes the problem at least a
little from the exposed football field example.Say the water table has risen to the bottom of the footing.If even more water was
introduced ouside the perimeter would that water not take that first and easy path to the drainage trenches.Of course I can also see
that the faster water is added would require wider and deeper trenches for a dry interior.
oldestguy (Geotechnical) 14
Sep
06
20:57
jtc500 The crawl space thing is different from what I had presumed. I was thinking of deep basement.
I suspect you are just trying to keep severe dampness from inside, as with "ponding in there". Your perimeter idea sounds good and
probably all that is needed in that case, assuming bottom of crawl space is a foot or more above your drain elevation. Hold off inside
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work until you see what outside work does.
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DECEMBER 2005 I JLC I 1
Foolproof Cure for Wet Basements
While listening to a home-improvement call-in
show on the radio the other day, I was struck
by the large number of callers who sought solutions to
wet-basement problems. Not surprisingly, the nation-
ally syndicated columnist who hosts the show said that
wet basements are the leading source of letters and
e-mails sent to his weekly newspaper column.
Barrier System vs. Water ManagementMy company, Tri-State Basement Systems, based in
Berlin, Vt., concentrates on basement waterproofing
and, as the radio show indicated, there is always plenty
of work. Unlike most DIY efforts and “miracle coat-
ings” that attempt to prevent ground-water entry with
a barrier, our techniques don’t try to stop the water, but
rather to manage it. Sometimes we use exterior
perimeter drains and waterproofing, but more often
we install water-management systems on the build-
ing’s interior. Most homeowners prefer this approach
because it costs less than excavating around the foun-
dation and is less destructive to their landscaping.
One recent project involved a 1950s ranch home with
a block foundation. The basement in this house was
literally soaking wet. Water running down the walls
accumulated on the floor, making the space virtually
unusable — even for storage. And when you opened
the basement door, you were greeted by a wave of
humid air and the pungent smell of mold. The home-
owner had tried numerous coats of waterproof paint,
grading around the foundation, and a cheap sump
pump illegally piped into the waste stack, but all these
efforts were of little help. Another contractor suggested
by Scott Anderson
Skip the exterior excavation and
waterproofing — an interior perimeter
drainage system can work just as well
DECEMBER 2005 I JLC I 2
Foolproof Cure for Wet Basements
Figure 2. The author’s crew often uses mattocks and hand trowels todig the trench along the inside of the footing (left). Next, workers drilla series of 3⁄8-inch weep holes along the base of the foundation wallwith a rotary hammer (above). Water often pours out of the wall forseveral seconds after a hole is finished. The bottom of the trench islined with a layer of crushed stone.
Figure 1. Electric jack-hammers are used to cut a trench around theslab’s perimeter. Thejackhammer makes lessdust than a concretesaw and can break uprocks or other obstruc-tions under the slab.Note the wet floor andmold on the walls.
excavating around the foundation and
installing a perimeter drain, but the plan
was twice as expensive as ours and
required removing a large deck.
So the homeowners decided to treat
the problem using the WaterGuard sys-
tem, one of the proprietary basement-
drainage systems manufactured and
supplied by our franchiser, Basement
Systems (800/638-7048, www.basement
systems.com). WaterGuard is a perimeter
drainage system installed on the inside
of the foundation. We dig a trench
around the perimeter of the basement
slab and install perforated pipe that
drains to a sump. The collected water is
pumped through a 2-inch pipe to the
building’s exterior. We give our custom-
ers a lifetime guarantee on the work we
do, and we almost never get callbacks.
TrenchingThe first step is to break up the floor at
the edges of the concrete slab to create a
5- to 6-inch-wide trench around the
perimeter. We use electric jackhammers
instead of concrete saws because the
jackhammers create less dust and can
cut through slabs of almost any thick-
ness (see Figure 1, previous page). Also,
the rough surface created by the jack-
hammer helps to key in the concrete
patch at the end of the process. As we’re
running the demo hammers, we carry
out the concrete rubble in five-gallon
pails.
Once the slab is cut around the
perimeter, we clean off the footing and,
just inside it, dig a small trench about
4 inches deep. While one or two crew
members are excavating the trench,
another drills a series of weep holes in
the base of the wall with a rotary
hammer (Figure 2, previous page).
Water stored in the cells of the concrete
blocks often pours out of the wall for
several seconds after a hole is drilled.
We line the trench with 2 inches of
crushed stone and install our propri-
etary WaterGuard drainage pipe, slop-
ing it toward the sump 1⁄ 4 inch over the
length of each wall. There are two
styles of WaterGuard pipe (Figure 3).
The standard version is placed directly
against the foundation wall with a plas-
tic flange extending up the foundation
wall. The flange is designed to leave a
small gap along the wall so any water
flowing down the wall can reach the
subslab drainage pipe (see “Basement
Interior Drain,” next page). The other
version works similarly, but comes in
two pieces. It’s used in applications
where the footing prevents placing the
drainage pipe against the foundation
wall. The pipe comes in 10-foot lengths
that we miter at the corners with an
inexpensive miter saw.
Installing the SumpWhile the drainage pipe is being installed,
we start digging the sump pit. Water often
fills the hole as we’re digging, so we need
to bail as we dig. Again, we use pails to
carry out the rocks and muck.
When the hole is finished, we place a
layer of washed stone in the bottom,
insert the sump liner — making certain
it’s level — and then backfill around the
basket with washed stone. We connect
DECEMBER 2005 I JLC I 3
Figure 3. The author uses two styles of proprietary pipe. The standard type (above) is placed against thefoundation wall. It has a toothed flange that creates a small gapbetween the basement wall and slab so any water seeping through the block is directed into the pipe. The job described here required the two-piece version (left) because the foot-ing prevented placing the pipe againstthe wall. The piping is sloped towardthe pump (below) — 1⁄4 inch over thelength of the wall is usually enough.
DECEMBER 2005 I JLC I 4
12"- to 16"-wide trencharound slab perimeter
Existing slab
Existing footing
WaterGuard drainage pipe withweep flange (allows any wall seepageto reach subslab drainage pipe)
One-Piece Drain
Two-Piece Drain
Perforated sump basket
Weep holes drilled along baseof existing block foundation
Pump stand
Discharge pipe
High-water alarm
Pump
Airtight floor drain
Existing footing
Existingblock wall
Crushed stone
Existing slab
Concrete patch
Crushed stone
Drilledweepholes
Concrete patch
Two-piece WaterGuarddrainage pipe, weep flangeplaced against wall
Basement Interior Drain
WaterGuarddrain outletadapter
Foolproof Cure for Wet Basements
WaterGuard drainage pipe comes in one-and two-piece configurations. The one-piecepipe installs more quickly, but the two-pieceversion is needed where there isn’t enoughspace to place the pipe between the slaband the top of the footing. Both types have aweep flange, which allows water seepingthrough the wall to reach the drainage pipe.
the sump basket to the WaterGuard pipe
with a proprietary adapter and a length
of 4-inch PVC (Figure 4).
The sump we use has features that
improve its performance and durability,
including a perforated basket to drain
water from below the floor and heavy-
duty plastic components. The high-qual-
ity Zoeller pump (800/928-7867, www.
zoeller.com) is placed on a plastic stand,
which prevents the pump from clogging
with sediment (Figure 5). The sump
basket has an airtight, two-piece, screw-
down lid to prevent kids and pets from
getting inside.
Running the Discharge LineWith the sump pump installed and the
cover in place, we run the discharge line
up the wall and across the ceiling to the
exterior. Ordinarily we take the most
direct route, but sometimes we’ll go out
of our way to place the outlet in an in-
conspicuous spot on the home’s exterior.
The discharge pipe is tucked inside a
joist cavity whenever possible so it won’t
interfere with finishing the ceiling.
DECEMBER 2005 I JLC I 5
Figure 5. A plastic stand (above) raisesthe pump about 6 inches above thebasket’s bottom so it doesn’t clog withsediment. Flexible couplings on thedischarge line (right) and a two-piece lid(far right) allow the pump to be removedwithout cutting the pipe.
Figure 4. An adapter (above)connects the uniquely shapedWaterGuard footing drain to a lengthof 4-inch PVC pipe that runs into thesump basket. Workers use a jigsaw to remove the knockout in the sumpbasket (above right); then they levelthe basket and backfill around it withwashed stone (right).
DECEMBER 2005 I JLC I 6
Where the pipe exits the house, we
seal the penetration with urethane
caulk and install a plastic trim ring for a
finished look.
Preventing the discharge line from
freezing is an important consideration in
our area, where winter temperatures can
stay below 0°F for days. If the outlet were
to freeze, the pump would still run, but
the backed-up water could cause a flood
or pump failure. We use a proprietary
outlet called an IceGuard, supplied by
our franchiser (Figure 6). It has openings
that allow the water to escape even if the
pipe below becomes clogged with ice or
debris. We also slope the discharge pipe
down toward the outside so water won’t
remain in the pipe near the outlet where
it’s more vulnerable to freezing.
To direct the discharged water away
from the foundation, we use a couple
of methods. The least expensive and
simplest option is to install a plastic tray
called a Rain Chute (Figure 7). The
chute has low-profiled sides so you can
mow right over it, and it’s placed in a
sloping trench so the water is carried
away from the house. We’re mindful of
where we locate the open-ended chute;
we don’t want the discharged water to
Figure 7. Because manyproperties may not haveenough slope or a conve-nient spot to drain todaylight, running a pipeunderground is not al-ways an option. In thesecases, a plastic traycalled a RainChute isinstalled in a slopingtrench to carry wateraway from the house(right). It’s placed slightlybelow grade so a mowercan run over it (far right).
Foolproof Cure for Wet Basements
Figure 6. Here, the dischargeline is placed on the front ofthe house, since a large deckblocked access to the bandjoist in the rear where water istypically discharged. A propri-etary IceGuard fitting allowsdischarge water to escape ifthe pipe freezes downstream.The fitting also acts as acoupling between the 2-inchpipe exiting the house and the4-inch exterior pipe.
pond in the yard.
Another option is to run an under-
ground pipe to daylight, but some home-
owners don’t want to damage their lawns
and some properties don’t have enough
slope for a daylight drain.
Finishing Touches After the pipe is run and the system
tested, we patch the concrete around the
sump, and cover the WaterGuard pipe
with at least an inch of concrete. The
only part of the pipe that’s visible is the
vertical lip that catches water running
down the wall. We also install a battery-
powered high-water alarm that alerts
the homeowner if the system is not
working properly (Figure 8). Often we
install fiberglass-reinforced panels over
the interior basement walls as a final
step. The plastic panels won’t support
mold growth, are easy to clean, and give
the basement walls a better appearance
(Figure 9).
Basement projects on small homes like
this 1,200-square-foot ranch typically
range from $1,500 to $8,000, depending
on the extras selected by the client.
Scott Anderson is the owner of Tri-State
Basement Systems in Berlin, Vt.
DECEMBER 2005 I JLC I 7
Figure 9. Many customers opt to finish the basementwalls with white fiberglass-reinforced panels (left), abig improvement over the moldy masonry typicallyfound in wet basements. The panels are fastenedwith drive anchors instead of adhesive, leaving spacefor seeping water to drain to the WaterGuard piping.These pictures were taken only a few days after thesump was installed. Note that the floor is completelydry (above).
Figure 8. Final steps includepatching the floor around thesump and basement perimeter(left) and installing a high-wateralarm (above) that sounds whenthe pump or discharge linemalfunctions. An emergency floordrain handles leaks — plumbingmishaps, a broken washing-machine hose, and the like.
A sloped finish
grade and properly
placed perimeter
drains will keep
the basement dry
A sloped finish
grade and properly
placed perimeter
drains will keep
the basement dry
s a concrete contractor, I have avested interest in how well the
water on site is controlled.Underground water and runoff
from rain and snow pose a threat both tothe structural integrity of the foundationsI build and to below-grade interior livingspace. Wet basements and cracked founda-tions are difficult to fix after the fact, butgood perimeter drainage, both at gradeand down at the footings, is a cheap andeasy way to prevent problems. If you fol-low these rules of thumb for perimetergrading and drain tile, you’ll sleep easyknowing that the water control systemsyou buried today won’t bubble up into acallback tomorrow.
Surface RunoffAlthough some wind-driven rain strikes
the siding and drains onto the ground,most surface runoff comes from the roof,and the amount of runoff varies accord-ing to the size and style of the roof. A
by Brent Anderson, P.E.
AFOUNDATIONDRAINAGEFOUNDATIONDRAINAGE
gable roof deposits all runoff onto the ground under theeaves, with little runoff at the gable ends; a hip roof distrib-utes the runoff more evenly on all sides (see Figure 1). Inaddition, valleys at main roof intersections and dormers canconcentrate runoff into a relatively small area on the ground.In cold climates, runoff increases significantly during springrainstorms when higher temperatures and rain combine tomelt snow on both the roof and the ground, adding to thetotal amount of surface water that must be drained awayfrom the foundation.
Sloped grade. Most basement water problems can be solvedby properly sloping the ground around the house. The finishgrade should slope away from the foundation at the rate of 1/2 to 1 inch per foot for 6 to 10 feet. A 2- to 4-inch cap ofsilty-clay material will keep runoff from percolating downthrough the backfill.
A sloped grade will not work for long, however, if the perime-ter fill is not mechanically compacted, which is rare in residen-tial construction. Instead, compaction is left to chance andoccurs slowly over a period of months or years, depending onclimate and the type of backfill used. Gravels and sands perco-
late faster and may reconsolidate more quickly — typically,from three months to a year. Silts and clays, which have a muchslower percolation rate, may not compact for several years.
In either case, however, the result is a negative grade thatdirects runoff back toward the foundation. Depending on thetype of backfill, sooner or later the runoff will overwhelm thefooting drainage system, and basement water problems willappear. Silt or clay fill, which hold water longer than gravel orsand, can make the foundation more susceptible to crackingfrom frost action; hydrostatic pressure may also develop withthese types of fill, forcing water through the slab-footing joint.Rarely will any of these problems appear immediately, butdown the road, you’ll be faced with a messy and expensiverepair job.
Gutters. While gutters can dramatically reduce the totalground area onto which roof water drains, it is crucial to usea sloped leader to extend downspouts along the ground tocarry water away from the foundation (Figure 2). Otherwise,a gutter-and-downspout system compounds the drainageproblem by concentrating the entire roof runoff load into afew small areas, usually at the house corners. Leaders should
MARCH JLC 1999
Note: Every inch of rain, whether it falls during a one-hour downpour oran all-day rain, deposits 1,500 gallons of water onto the ground around atypical 2,500-square-foot roof surface. During a winter rainstorm, everyfoot of melting snow on the roof adds an additional 1,500 gallons.
Concentratedrunoff at valleyand dormer
Less runoffat hip
Gable Roof Runoff Hip Roof Runoff
Roof Runoff(from 2500 sq. ft. roof)
Rainfall Rainfall Volume VolumeAmount Rate (cubic ft.) (gallons)
1 in. per hr. 200 1,500
1 in. per day 200 1,500
2 in. per hr. 400 3,000
2 in. per day 400 3,000
Figure 1. Both of these roofs coverapproximately 2,500 square feet. Thegable roof deposits runoff along twosides of the house; the hip roof spreadsthe runoff more or less evenly along allsides. Main roof valleys and dormersconcentrate the runoff into smaller areason the ground.
Concentratedrunoff at valleyand dormer
Roof runofffalls to groundat eaves
Less runoffat hip
MARCH JLC 1999
Downspout
Leader dischargesonto sloped ground
Finish grade slopes1/2" to 1" per foot for 10'
10'-0"
2" to 4" clay capover backfill
Downspout with Sloped Leader
Downspout with Catch Basin
Figure 2. Sloped down-spout leaders shoulddischarge at least 10feet away from thefoundation wall (top).Use solid drain pipe tocarry runoff from a con-crete catch basin todaylight or a drywell(bottom).Downspout
Filter fabric or grateto prevent clogging
24" x 24" concrete catch basinwith water-tight bottom
Solid pipe, drain todaylight or drywell
Crushedstone
Buried rigid foam aroundcatch basin (optional)
MARCH JLC 1999
Figure 3. A properly sloped con-crete or paver sidewalk will reducethe amount of runoff that perco-lates through the backfill (left).Where perimeter plantings areused to landscape, improvedrainage by burying a sheet ofpolyethylene below the plant bed,with openings cut out for roots(below). Tie shallow perforateddrain tile to solid pipe to carrywater to daylight or a drywell.
Grade min. 8"-12" below sidingto avoid splashback
Concrete or paver sidewalkcovers full width ofbackfilled area
Concrete or Paver Sidewalk
Crushed stone orwood chips
Filter fabric
Cutopeningsin poly forroots
Buried polyethylene
Perforateddrain tile
Plant Bed with Drain
discharge onto sloping ground at least 10 feet from the foun-dation. If downspouts dump directly into a catch basin on thesurface or underground, the collected runoff should be carriedthrough a solid drain pipe to a drywell or to daylight.
Keep gutters clear of leaves, pine needles, and ice. Overflowfrom blocked gutters can follow the contour of the gutter andsaturate the soffit and siding, often making its way into thewall and wetting the insulation, drywall, and floor. Similarly,gutters in cold climates can encourage ice damming, with thesame damaging results.
Hardscape. Concrete or paver block sidewalks can also con-trol percolation of runoff into the backfill (Figure 3) — I’vemeasured reductions in runoff percolation of between 300%and 500%. Again, the hardscape should be wide enough to
cover the entire backfilled area, and the surface should slopeaway from the foundation walls.
A less expensive technique is to bury a sheet of polyethylenein a plant bed. The poly should cover the backfilled founda-tion trench and slope to a perforated drain tile laid parallel tothe foundation. Use solid pipe to carry runoff to daylight or toa drywell. In landscaped areas, cut openings in the poly toaccommodate plant and tree roots.
Buried poly works well, so long as the backfill has beencompacted. With a negative grade, however, the poly actuallydirects the water into the foundation wall. Plant and treeroots near the foundation can also compound problems withuncompacted fill, because their root systems absorb waterand cause the soil to reconsolidate quickly. In a drought, tree
roots can pull so much moisture out of the soil that the foun-dation may settle.
Perimeter Footing DrainsFoundation perimeter drains work in both directions. They
not only carry rainwater percolating down through the back-fill away from the foundation, they also relieve excessivehydrostatic pressure from rising groundwater. By helping thebackfill dry out more quickly, properly installed perimeterdrains reduce lateral soil pressure, which in turn means thatfoundation walls can be designed to use more porous materi-als and less steel.
There’s a right way and a wrong way to install perimeterdrainage. Unfortunately, many foundation contractors andhome builders labor under a false sense of security, reasoningthat if complaints about leaky basements don’t surface withinthe first year or two after a project is completed, their con-struction techniques must be working. The fact of the matteris that basement water problems that occur within the firsttwelve months are usually related to waterproofing defects.Drain tile problems typically take many years to develop.Thus, many contractors have buried time bombs that willeventually blow up in their faces.
Holes DownAlthough porous cement-based tile is still in use today, most
residential contractors would agree that perforated 4-inch-diameter plastic pipe produces tighter joints and is easier towork with. Not all would agree, however, on which directionto place the holes in the pipe when installing footing drains.
The answer depends on the type of pipe. Flexible HDPE(high-density polyethylene) is slotted all the way around, andsome rigid PVC has a pattern of holes around the entire cir-
cumference. With these types of drain tile, there is no “right”direction because there are openings on all sides. Pluggedholes on the bottom are cleared by water entering through thesides and top.
The most popular drain tile, however, is rigid PVC that hasjust two parallel rows of holes close together along its length.The classic approach is to lay this type of drain tile with theholes facing down, in the five-o’clock and seven-o’clock posi-tions. This allows a rising water table to enter the pipe at itslowest point.
Filter fabric. While hydrostatic pressure helps to flush siltfrom the pipe, all buried drain tile should be surrounded withcoarse gravel or crushed stone, and wrapped with a filteringmaterial. Without a filter, silt will contaminate the stone andeventually enter and plug the holes in the pipe (Figure 4).Various geotextiles are available in rolls, and pre-wrapped or“socked” pipe — pipe that is manufactured with a filter sleevealready in place — is also available.
Drain Tile LocationFilter paper and properly oriented perforations, however,
will not guarantee that drain tile will work. The pipe must alsobe installed carefully and in the right location with respect tothe footing and any interior slab.
From a pure engineering point of view, the ideal place to layexterior drain tile is alongside the footing, because water froma rising water table enters the pipe sooner (Figure 5). The draintile does not need to be sloped, although a slight pitch helpskeep the pipe clear of silt and clay (particularly when the pipehas just two rows of holes on the bottom). Avoid trying toslope flexible drain tile, however, because you can inadver-tently create dips and sags that will eventually collect silt andclog the pipe (Figure 6). In fact, undulating drain tile can
MARCH JLC 1999
Figure 4. Without a filter to keep silt from contaminatingthe surrounding stone, drain tile can be rendered uselesswithin just a few seasons (left). Pipe that is pre-wrappedor “socked” with filter material will prevent drain tile frombecoming plugged (above).
result in premature failure of the drainage system. This prob-lem is more pronounced when trees are growing close to thefoundation, because wet silt and clay accumulating in lowspots become targets for water-seeking tree roots in dry peri-ods or in dry climates. In a relatively short period of time, treeroots can completely plug drain tile.
Some contractors create an even lower elevation for the tileby digging a small trench next to the footing. To avoid under-mining the foundation, however, most codes require that thetile be placed outside a 60-degree angle from the footing.
Drain tile can also be placed on top of the footing. Theadvantage here is that the tile will be as level as the footing —a good strategy when using flexible pipe (Figure 7). But thishigher placement doesn’t control a rising ground water tableas effectively, and may require raising the elevation of theinterior slab.
Specialty drainage products. Today there are several prod-ucts on the market, such as Form-A-Drain (CertainTeed
Corp., P.O. Box 860, Valley Forge, PA 19482; 800/233-8990;www.certainteed.com), that provide both the footing formand the drain tile (Figure 8). These systems not only ensurethat the drainage system is level, they often provide moreflow capacity than traditional pipe systems.
On sites where an exceptionally high ground water tablecreates intermittent hydrostatic pressure on the foundationwalls, dimpled sheets can be used in conjunction with stan-dard drain tile. These membrane systems provide a water-proof barrier while also directing excess ground water fromhigher up on the foundation walls into the perimeterdrains.
Discharging Collected WaterCapturing ground water in a perimeter drainage system is
only half the battle — once you’ve collected water in thedrain tile, you have to dispose of it somewhere. Dischargingwater into sanitary sewer systems is generally illegal, which
MARCH JLC 1999
Filter fabric
Drain tile min.6" below topof slab
6"
12"Minimum stonedepth around threesides of pipe
2"
Pipe at Bottom of Footing
Filter fabric
Drain tile min.6" below topof slab
12"
12"Maintain 60°shoulder to avoidundermining footing
Pipe Below Footing
Figure 5. The best location for rigid drain tileis alongside the footing. Minimum require-ments for stone cover depend on whether thetile is flush with the top of the footing (topleft) or the bottom (above). In either case, thetop of the interior slab should be at least 6inches above the top of the drain tile. Thepipe can be laid level or pitched slightly.
Where drain tile must be located lowerthan the bottom of the footing (left), avoidundermining the footing by keeping the pipeoutside of a 60-degree angle measured fromthe corner of the footing. This location alsorequires more stone cover for the pipe.
Pipe Even with Top of Footing
Filter fabric
Stone coverextends min.6" over pipe
Drain tile min.6" below topof slab
6"
6"6"
MARCH JLC 1999
Figure 8. Form-A-Drain stay-in-place footing forms ensure a levelperimeter drain and have a larger capacity than pipe systems(above). To control hydrostatic pressure, dimpled drainage panelsfastened against the foundation wall carry water from the backfillinto the perimeter drains (right).
Filter fabric
Top of pipe shouldnot be higherthan top of slab
12"
Flexibledrain tile(slotted)
12"
2"
Pipe Resting on Footing
Figure 7. To keep flexible drain tile fromdeveloping low spots that will collectsilt, place it on top of the footings, mak-ing sure that the top of the pipe is nothigher than the top of the interior slab.
Figure 6. Regardless of the type of pipe used or its shape, unfiltered drain tile can easily be plugged with silt and clay (left).Water-seeking roots from trees growing too near the foundation can also completely clog perimeter drains (right).
leaves two basic ways to get rid of the water: On sloped sites,you can extend unperforated drain tile to daylight and dis-charge the water on the ground; on flat sites, you can collectthe water in a sump basket and pump it to a discharge areaaway from the basement.
Gravity discharge. Two elements are critical to proper func-tion of a gravity drainage system. First, although the perforateddrain tile around the foundation itself may be level, solid piperunning from the foundation to daylight should slope at therate of 1/16- to 1/8-inch per foot. Second, the open end of thedischarge line should prevent entry by rodents, frogs, snakes,and reptiles. One method is to cover the exposed end of thepipe with 1/4-inch hardware cloth. Alternatively, you can burythe end of the pipe in crushed stone, which will allow thewater to seep out below grade.
Pumped discharge. While gravity discharge to daylight ischeap and easy, I recommend installing a sump basket as abackup. A submersible sump in the bottom of the sump bas-ket connects to a hose or rigid pipe system that carries thecollected water out of the basement. If you provide for the
collection sump at the time the foundation and slab areplaced, the pump and discharge piping can be installed laterif needed.
The sump basket should be located inside the foundation,where it can pick up ground water that rises under the slab.On a flat site where all ground water must be pumped away,water from perimeter drains should also be directed into thesump through drainage sleeves in the footing (Figure 9). Toavoid having to excavate later, be sure to place sleeves beforethe footings are poured. Use 4-inch-diameter pipe, and spacesleeves 6 to 8 feet apart around the entire perimeter of thefooting. In special cases where the slab is placed a foot or moreabove the top of the footings, you can locate sleeves in thefoundation wall. Although water passing through the sleevesor under the footing will generally find the sump basket on itsown, I recommend an interior drain pipe at the perimeter, ter-minating in the sump basket.
Brent Anderson owns and operates Brent Anderson Associates, aconcrete contracting and consulting firm in Fridley, Minn.
MARCH JLC 1999
Filter fabric Discharge collectedwater at least 10'away from foundation
Sleeve throughconcrete footing
Clay, plastic,or concretesump basket
Submersiblepump
12"
12"
Hose or rigidPVC discharge pipe
Interior draintile at perimeter
60°
Interior Sump Basket
Figure 9. An interior sumpbasket picks up excess waterflowing through sleeves inthe footing (photo). A sub-mersible pump connected toa hose or rigid pipe dis-charges the water on theground away from the foun-dation (illustration).
PM Home Page » Home Journal » How-To Central » Other Topics
Basement Blues
Untamed runoff can sink your house. Fight back. BY MERLE HENKENIUS Illustrations by Thomas Klenck Published in the April, 2005 issue.
1 2 3 Next
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If you have trouble with basement water, you're not alone. We spoke with Douglas Pencille, a Minnesota housing inspector with firsthand experience. "I visit 1300 to 1500 houses per year and 30 to 40 percent of them have basement water damage. It's a big problem, often requiring corrective action." What kinds of corrective action?
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It all depends on the source of the water.
Water From Above ... The most common cause of basement water is unmanaged rain runoff. Rainwater from the roof flows down through the soil and collects at the bottom of the original foundation excavation. While the weight of the saturated earth alone can break a wall, the situation worsens when the water freezes and exerts a lateral force that can cause cracks and buckling. How do you know when water damage is from runoff? When leaks follow substantial rains and when the soil around the foundation appears settled.
The solution is a well-maintained gutter system that uses downspout extensions to carry roof runoff at least 4 ft. from the foundation wall. Also, the grade next to the wall must be sloped to direct surface water away from the house.
... And Below Groundwater problems can result from a high water table or an underground spring. Sometimes the problem is seasonal, coinciding with spring snowmelts and heavier rains, but it can occur at any time. Ground-water doesn't usually break walls, but it can flood the basement floor.
Exterior draintiles around the perimeter of the foundation footing are the first line of defense against groundwater. The simplest retrofit solution is to install a sump pump that carries the water away from the house. An interior draintile system is effective in routing water from the entire basement to the sump.
For background information on how house construction works, click here
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Accessory ● Choosing The Right Broom ● Old Glory: America's Flag
and How to Fly It ● How To Repair Your
Driveway ● Techniques: Chisel Basics ● Buying A Central Air
Conditioning System ● Appliance Care: Replacing A
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● Installing A Tile Counter
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PM Home Page » Home Journal » How-To Central » Other Topics
Basement Blues
Untamed runoff can sink your house. Fight back. BY MERLE HENKENIUS Illustrations by Thomas Klenck Published in the April, 2005 issue.
Previous 1 2 3 Next Foundation Repairs: If your foundation walls have cracks or they've buckled, you can do much of the repair work yourself or hire a contractor to handle the job. The newer techniques that use high-tech materials and sophisticated hardware require specialized skills so you'll need to hire a professional.
Traditional Fixes
WALL REBUILD One solution to a buckled block wall is to replace it. You can do this without excavating. First, use post jacks and a 4 x 6 beam to take the load from the wall. Then, remove the damaged section down to the footing. After rebuilding the wall, wait several days before removing the jacks.
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EXCAVATION AND REPAIR To keep the original wall, excavate the area outside. Then, use a jack and a few wooden beams to nudge the wall back into position. Repair any bad mortar joints, and consider improving your drainage system to reduce hydrostatic pressure and to direct water away from the house.
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Mistakes ● Creating Shade In Your
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When Not To ● Holiday Appliance Care Tips
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WALL BRACING If you don't want to replace the wall or excavate, try bracing. Vertical steel I-beams set in holes in the floor and fastened to steel braces at the ceiling joists can keep a wall in place. Local building codes vary, though, so make sure this approach is approved in your area.
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Accessory ● Choosing The Right Broom ● Old Glory: America's Flag
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Driveway ● Techniques: Chisel Basics ● Buying A Central Air
Conditioning System ● Appliance Care: Replacing A
Refrigerator Condenser Fan Motor
● Installing A Tile Counter
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PM Home Page » Home Journal » How-To Central » Other Topics
Basement Blues
Untamed runoff can sink your house. Fight back. BY MERLE HENKENIUS Illustrations by Thomas Klenck Published in the April, 2005 issue.
Previous 1 2 3 Modern Approaches
BRACING WITH BELTS This system replaces I-beams with carbon-fiber/Kevlar belts (Fortress Stabilization Systems, 800-207-6204; www.fortressstabilization.com). A contractor grinds 1/8-in. recesses across the cracks. The belts are coated with epoxy and set in place, and the epoxy is trimmed flush with the wall.
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WALL-ANCHOR REPAIR Wall anchors (Grip-Tite Manufacturing, 515-462-1313; www.griptite.com) consist of two steel plates, one located on the inside of the wall and the other buried in the ground outside, and a threaded rod connecting the plates. Tightening a nut on the rod draws the wall flat.
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LIFTING WALLS When footings settle they can be repositioned with push piers (Foundation Pier System, Grip-Tite Manufacturing). Hydraulic drivers placed around 3 to 6 ft. apart push steel piers down to the bedrock while support brackets restore the footing to its original level.
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Copyright © 2006 Hearst Communications, Inc. All Rights Reserved.
When you live on a barrier island,
just keeping your little piece of
real estate from washing away is a con-
stant struggle. Fred Sprinkle, a foundation
and excavation contractor on Dauphin
Island, Ala., frequently uses vinyl sheet pil-
ings to keep the ground beneath his
clients’ homes from ending up in the Gulf
of Mexico.
His employees — who spend as much
time in the water as they do on land, and
dress accordingly — start one of their
vinyl seawalls by building a frame of pres-
sure-treated wood pilings and dimen-
sional lumber (1). The lumber and pilings
are CCA-treated; newer pressure-treating
formulas don’t hold up as well in salt-
water and aren’t as resistant to marine-
boring organisms.
SEPTEMBER 2006 I JLC I 1
On the Job
Installing Sheet Piles
1
2
Once the frame is assembled, the crew
ties it to dry ground with stainless-steel
threaded rods and earth anchors (2, pre-
vious page).
Next, workers use a gas-powered pump
(3) to wash holes in the sea floor for the
12-inch-wide piles. The pump sends
water first through a 2-inch hose and
then through a 11⁄2-inch steel pipe (4);
the transition from a larger to a smaller
diameter increases head pressure. The
pipe’s weight makes controlling and
directing the stream of water easier.
Once the holes are made, the crew
pushes the 12-foot-long sheet pilings in;
some piles go easy, and others require
persuasion with a sledge or a small pneu-
matic jackhammer (5). All have mating
edges that lock them together (6, page
48). They’re nailed to the wood frame at
the top and at the water line.
The walls’ integrity depends on how
deep the pilings are placed in the sand.
On the Job l Installing Sheet Piles
3
4
5
SEPTEMBER 2006 I JLC I 2
The day I visited, workers were replacing
a poorly built wall with one that went
about twice as deep.
Unscrupulous contractors often use
shorter pilings to save time and money,
but occasionally even competent install-
ers face an obstacle that makes it impos-
sible to drive the pilings to their intended
depth.
When Sprinkle’s employees run into
this problem, they try to remove the
obstacle any way they can. Sometimes
they keep enlarging the hole till they can
pull the object out by hand; other times
they lug it out with a chain connected to
their excavator or backhoe (7). Only as a
last resort do they cut the pile shorter.
Once all the piles are installed, the area
is backfilled with sand and the wall is fin-
ished with a pressure-treated cap.
This kind of work may sound like a day
at the beach, but crew members told me
cuts and puncture wounds on hands and
feet — plus nasty sunburns — are com-
mon. They also said that despite the large
retrieval magnet kept permanently in the
truck, they lose hammers and other hand
tools regularly. — Patrick McCombe
SEPTEMBER 2006 I JLC I 3
On the Job l Sheet Piles 6
7
Installation Guide
RR
www.hardiepipe.com
This Installation Guide is offered to provide you guidance inthe proper unloading, handling, and installation of Hardie® Pipe.
Hardie Pipe, a division of James Hardie® Building Products,Inc., is The Next Generation of Concrete Pipe. It is importantthat proper handling and installation procedures are followedto ensure a long-lasting, trouble-free concrete pipeline.
Please contact our Customer Service Department toll-free at877-910-3727 from 7AM to 5PM EST, Monday through Fridaywith any questions or comments you may have about thehandling or installation of Hardie Pipe as it pertains to yourproject.
The information contained in this booklet is based on fieldexperience and sound engineering judgment in accordancewith standard concrete pipe installation practices as found inASTM C1479. It should in no way be used to override or deviate from the specifications and/or engineering drawingsprovided for your specific project.
Ordering Procedures & Customer Support
Hardie® Pipe Arrives on the Jobsite
Unloading Hardie Pipe from Flatbed Truck
Storing Hardie Pipe on the Jobsite
Handling Hardie Pipe
Preparing the Pipe Trench
BeddingHaunchLower SideOverfill ZoneExcavation LimitsDewateringStandard Installations
Jointing
Installing Gaskets & Applying LubeMaking the Pipe Joint
Minimum Cover for Construction Loads
Connecting Hardie Pipe to Structure/Manhole
Field Cutting Hardie Pipe
Hardie Pipe Warranty
Appendix
Hardie Pipe Field Repair Procedures
Cracked or Chipped JointPuncture HolesSurface ImperfectionsGouging
Bundling Standards Pipe Nominal Weight Chart Shipping Specifications Nominal Pipe OD’s Joint Gap TolerancesCenter Stripe Color Code
Table of Contents
3
4
5
6
8
9
11
13141414151516
19
1921
24
25
26
29
30
30
30313334
353839404142
Ordering Procedures & Customer Support
Coordination between the contractor, supplier and engineer isrecommended to avoid mistakes and possible delays in pipedeliveries. Although Hardie® Pipe stocks a wide range of pipesizes and classes, it is important to follow proper lead time procedures provided by the Customer Service Department.Hardie Pipe maintains an experienced staff to help youachieve the most cost and time-efficient installation. Our professional team is available to provide guidance aboutHardie Pipe.
To initiate a pipe order, please contact your local representative or the Hardie Pipe Customer ServiceDepartment at 877-910-3727.
4
5
Hardie® Pipe Arrives on the Jobsite
Always confirm pipe shipment with bill of lading Before Signing:
If there are any discrepancies on the bill of lading, contact
the Hardie® Pipe Customer Service Department
(877-910-3727) between the hours of 7AM and 5PM EST,
Monday through Friday.
√ Jobsite/Project√ Pipe Quantity√ Pipe Class√ Pipe Diameter
√ Quantity of Gaskets (Normal or Oil Resistant)
√ Lube√ Certification Stamp
(if applicable)
Figure 1 - Hardie Pipe Arriving at Jobsite
6
Unloading Hardie® Pipe from Flatbed Truck
Coordinate delivery and unloading with the constructionschedule to avoid re-handling and unnecessary equipmentmovement. It is the responsibility of the contractor to ensurethat Hardie® Pipe delivery trucks have full access to theunloading area.
For ease in shipping and offloading, Hardie Pipe is bundledand banded together in standard quantities as listed in theAppendix in Table 5 and loaded on flatbed trucks as listed inTable 7.
Caution: Consult Nominal Pipe Weight Chart (Table 2) and
Confirm Proper Equipment Used for Unloading Hardie Pipe.
Hardie Pipe is longer than traditional steel reinforced concretepipe. It is important to center the load on your equipmentbefore the pipe is lifted off the truck. Follow the manufactur-er’s guidelines and safety procedures for the specific piece ofequipment used to unload the pipe.
Figure 2 - Never Roll Hardie Pipe off the truck!
7
Use of a forklift is recommended when offloading Hardie® Pipe. Depending upon equipment, fork extensionsmay be used if designed to properly support the load of thepipe bundle.
Note: Please consult Nominal Pipe Weight Chart Table 6 of
the Appendix
Align Forks on pipe as shown in the picture above and placeHardie Pipe on ground as appropriate.
Hardie Pipe does not recommend cutting the steel bands
bundling the pipe together until safely stored on the jobsite.
However, if it is necessary to cut the bands while on the
truck, please take safety precautions to stabilize the pipe on
the pallet AND the remaining pipe on the truck.
Contact your local sales representative or Hardie PipeCustomer Service Department if you are not sure aboutoffloading procedures.
Figure 3 - Forklift With Pipe Bundle Centered Over Forks
Storing Hardie® Pipe on the Jobsite
Hardie® Pipe should be stored properly on your jobsite to prevent unnecessary damage to the pipe and gaskets.
Be sure to keep stored gaskets out of direct contact with sunlight to prevent the rubber from experiencing UV damage.
Storage area must be a level area with a stable base.
Hardie Pipe may be stored on site as shown in the diagramabove. Pallets of pipe may be stacked up to 8-feet high if thefollowing conditions are met:
� Pipe must be aligned in the same direction.� Pallets must be aligned in the same direction.� Pallets must be centered on the lower bundle.� No cantilever pipe or pallets are allowed.
8
Figure 4 - Proper Storage of Hardie Pipe Figure 5 - Improper Storage of Hardie Pipe
9
Handling Hardie® Pipe
Hardie® Pipe should be picked up and handled using properlyrated rigging equipment capable of lifting appropriate load(See Table 6 of the Appendix).
Care should be taken to insure that the pipe ends are notdamaged and worker safety is maintained while maneuveringHardie Pipe around the jobsite and setting Hardie Pipe into the trench. Pipe should be carried level to avoid damagingjoints. A center stripe is painted on the pipe during manufacturing to aid in locating the center of the load. Thecolor of the stripe designates the class of the pipe (See Table 10 in the appendix).
It is the responsibility of the contractor to locate the true cen-ter of the pipe for lifting and to handle loads safely.
Align rigging along center stripe as shown in picture below:
When picking up Hardie Pipe,use worker or tether line toguide end of pipe.
Caution: As Hardie Pipeis Lifted and Moved,Watch for “Pinch Points.”
Do not lift
Hardie Pipe
off set from the
center stripe
Figure 6 - Recommended Lifting and Handling
Figure 7 - Improper Lifting and Handling
10
Do not lift
pipe with
forks
inside pipe
Do not lift pipe
with slings
inside pipe.
If damage occurs to the pipe while handling, consult the field repair procedures in the appendix of thisinstallation booklet. If bell or spigot is damaged beyondrepair, cut the damaged section of pipe back to sound, solidmaterial and use this undamaged piece to come into or out ofa manhole/junction box.
Figure 8 - Improper Lifting
Figure 9 - Improper Lifting
11
Preparing the Pipe Trench
Hardie® Pipe is a concrete pipe that should be installed inaccordance with ASTM C1479. See Table 8 of the appendix forOD’s by diameter and pipe class.
When preparing the pipe trench, care should be taken toassure that the foundation is free of rock, hard, lumpy, orother unyielding material. The foundation shall be moderatelyfirm to hard in situ soil, stabilized soil, or compacted fill material. Remove muck or other soft material to a depth necessary to establish a firm foundation. If the trench isundercut to remove undesirable foundation material, theundercut area must be filled and compacted to the level of thebedding zone of the pipe. Backfill undercut areas withapproved materials compacted to at least the same density asthe bedding material.
Trench grades should be monitored to assure compliance withspecified grade. Failure to maintain proper grade can result inhigh and low spots in the pipeline, which can affect thehydraulic capacity of the line as well as prevent proper bedding of the pipe.
Figure 10 - Pipe / Installation Terminology
12
Figure 11 - Standard Trench Installation
Figure 12 - Embankment Installation
13
Bedding
Uniformly construct bedding over the entire length of the pipebarrel, near structures, to distribute the load-bearing reactionevenly to the bedding over the full length of the pipe barreland to maintain the required pipe grade. Bedding under themiddle third of the pipe diameter shall be loosely placed, anduncompacted prior to placement of the pipe. Any outer bedding shall be compacted to the requirements for the specific Standard Installation type.
Do not make adjustment in grade by lifting and dropping thepipe, by pushing down on pipe with excavating equipment orby lifting the pipe and packing bedding material beneath thepipe. Pipe not on grade shall be completely removed, thegrade corrected and the pipe rejoined.
Note: Ensure that bedding is free of rock, hard, lumpy or
other unyielding material.
Figure 13 - Pipe Bedding and Foundation
14
Haunch
Construct the haunch using the specified soil type and compaction level required for the designated installation.Haunch material shall be placed and compacted uniformly overthe entire length of the pipe barrel, near structures, to distribute the load-bearing reaction evenly to the bedding overthe full length of the pipe barrel. Maximum aggregate sizeused in the haunch area shall not be greater than 1-inch.Compact uniformly placed soil on either side of the pipe to thespecified density to prevent lateral displacement of the pipe.
Lower Side
Soil placed in the lower side shall not contain debris, organicmatter, frozen materials or large stones with diameters greaterthan one half the thickness of the compacted layer beingplaced. The lower side shall be constructed using a specifiedsoil type and minimum compaction level. When placed in layers, the layers shall be of a thickness required to achieve thespecified compaction as required by the project specifications.
Overfill Zone
Soil placed in the overfill area shall be material conforming tothe project specifications. This material shall contain no debris,organic matter, frozen materials or large stones with diametersgreater than one half the thickness of the compacted layerbeing placed. When placed in layers, the layers shall be of athickness required to achieve the specified compaction and asrequired by the project specifications. To prevent lateral displacement of the pipe, place and compact soil uniformly oneither side of the pipe to the specified density. The overfillplaced within one outside diameter of the pipe, that is abovethe spring line, and below top of the pipe, shall be compactedto at least the same density as the majority of the overfillabove the pipe. Take care not to damage pipe when usingimpact or vibratory equipment to compact soils in pipe trench.
Do not allow heavy construction or compaction equipment tocross over pipe until backfill is compacted to an elevation of atleast 3 feet above the crown of the pipe.
15
Excavation Limits
Trench width and depth directly affect the backfill load transmitted to the pipe. The pipe class specified is determinedbased upon the trench width and depth assumed duringdesign. To avoid overloading the pipe, the trench width shouldnot exceed that which is stated on the project plans and specifications without consulting with the design engineer.
Dewatering
Backfill should be placed in the dry. Dewater trench to providedry conditions during excavation and installation.
Where dewatering by normal pumping methods is ineffective,uniform bedding of a select granular material shall be placedthroughout the entire run of pipe. Uniformly construct bedding over the entire length of the pipe barrel, includingnear structures, to distribute the load-bearing reaction evenlyto the bedding over the full length of the pipe barrel and tomaintain the required pipe grade.
16
Standard Installations
Hardie® Pipe is a concrete pipe that should be installed inaccordance with the Standard Installations as shown in ASTM C1479. These standard installations are listed below.TABLE 1 - SOILS AND MINIMUM COMPACTION REQUIREMENTSInstallation
TypeBedding Thickness Haunch and
Outer BeddingLower Side
Type 1 Do/24 minimum, notless than 3” (75mm). Ifrock foundation, useDo/12 minimum, notless than 6” (150mm)
95% CAT I 90% CAT I,95% CAT II,
or100% CAT III
Type 2 Do/24 minimum, notless than 3” (75mm). Ifrock foundation, useDo/12 minimum, notless than 6” (150mm)
90% CAT Ior
95% CAT II
85% CAT I,90% CAT II,
or95% CAT III
Type 3 Do/24 minimum, notless than 3” (75mm). Ifrock foundation, useDo/12 minimum, notless than 6” (150mm)
85% CAT I,90% CAT II,
or95% CAT III
85% CAT I,90% CAT II,
or95% CAT III
Type 4 No bedding required,except if rock
foundation, use Do/12minimum, not less than
6” (150mm)
No compactionrequired, except ifCAT III, use 85%
CAT III
No compactionrequired, except ofCAT III, use 85%
CAT III
NOTES:1. Compaction and soil symbols -i.e. “95% CAT I” refer to CAT 1 soil materials with a minimum standard proctor compaction of 95%.2. Soil in the outerbedding, haunch, and lower side zones, except with Do/3 from the pipe springline, shall be compacted to at least the same compaction as the majority of the soil in theoverfill zone.3.SUBTRENCHES3.1 A subtrench is defined as a trench with its top below finished grade by more than 0.1H or, forroadways, its top is at an elevation lower than 1’ (0.3m) below the bottom of the paved basematerial.3.2 The minimum width of a subtrench shall be 1.33 Do, or wider if required for adequate space toattain the specified compaction in the haunch and bedding zones.3.3 For subtrenches with walls of natural soil, any portion of the lower side zone in the subtrench wall shall be at least as fim as equivalent soil placed to the compaction requirementsspecifiedfor the lower side zone and as firm as the majority of soil in the overfill zone, or shall beremoved and replaced with soil compacted to the specified level.
17
Table 2 - SOILS AND MINIMUM COMPACTION REQUIREMENTSInstallation
TypeBedding Thickness Haunch and
Outer BeddingLower Side
Type 1 Do/24 minimum, notless than 3” (75mm). Ifrock foundation, useDo/12 minimum, notless than 6” (150mm)
95% CAT I 90% CAT I,95% CAT II,
or100% CAT III
Type 2 Do/24 minimum, notless than 3” (75mm). Ifrock foundation, useDo/12 minimum, notless than 6” (150mm)
90% CAT Ior
95% CAT II
85% CAT I,90% CAT II,
or95% CAT III
Type 3 Do/24 minimum, notless than 3” (75mm). Ifrock foundation, useDo/12 minimum, notless than 6” (150mm)
85% CAT I,90% CAT II,
or95% CAT III
85% CAT I,90% CAT II,
or95% CAT III
Type 4 No bedding required,except if rock founda-tion, use Do/12 mini-mum, not less than 6”
(150mm)
No compactionrequired, except ifCAT III, use 85%
CAT III
No compactionrequired, except ofCAT III, use 85%
CAT III
NOTES:1. Compaction and soil symbols -i.e. “95% CAT I” refer to CAT 1 soil materials with a minimum standard proctor compaction of 95%. 2. The trench top elevation shall be no lower than 0.1H below finished gradeor, for roadways, its topshall be no lower than an elevation of 1’ (0.3) below the bottom of he pavement base material.3. Soil in bedding and haunch zones shall be compacted to at least the same compaction as specified for the majority of soil in the backfill zone.4. The trench width shall be wider than shown if required for adequate space to attain the specifiedcompaction in the haunch and bedding zones.5. For trench walls that are within 10 degrees of vertical, the compaction or firmness of the soil inthe trench walls and lower side zone need not be considered.6. For trench walls with greater than 10 degree slopes that consist of embankment, the lower sideshall be compacted to at least the same compaction as specified for the soil in the backfill zone.
18
TABLE 3 - SOIL DESIGNATIONSSIDD Soil Representative Soil Types Percent Compaction
USCS AASHTO StandardProctor
ModifiedProctor
Gravelly Sand(CATI)
SW, SPGW, GP
A1, A3 1009590858061
959085807559
Sandy Silt(CAT II)
GM, SM, MLAlso GC, SCwith less than20% passing#200 sieve
A2, A4 1009590858049
959085807546
Silty Clay (CAT III)
CL, MHGC, SC
A5, A6 1009590858045
100959045
908580757040
90858040
19
Jointing
Installing Gaskets and Applying Lube
Carefully clean all dirt and foreign substances from the jointing surfaces of the bell and spigot end of Hardie® Pipe,including the gasket groove. Gaskets should not be placed onHardie Pipe until pipe is ready to be installed. Confirm thatgasket diameter matches pipe diameter. Install gasket onspigot end of pipe in the machined gasket groove and oriented in the proper direction as illustrated below:
Caution: Be sure that
gasket is seated
properly in machined
gasket groove and
free of any soil,
twists, or abrasions to
insure proper joint
seal is made.
Figure 14 - Properly Seated Gasket
Figure 15 - Improperly Seated Gasket
After gasket is in place, generously apply lube to Hardie® PipeBELL END ONLY as shown below:
Be sure to apply a generous amount of lube along the entiresurface of the pipe bell to allow for easy installation.
Note: For wet conditions use a subaqueous lube.
Figure 16 - Lubrication of Bell
20
Figure 17 - Lubrication of Spigot
21
Making the Pipe Joint
Proper safety measures should be implemented when working in trenches and confined spaces in accordance withjobsite safety instructions.
Before laying Hardie® Pipe into the pipe trench, be sure thatbedding material is set to proper line and grade.
Lower Hardie Pipe into trench. Hardie Pipe can be laid ineither direction as long as care is taken to put the jointtogether properly and keep debris out of the joint duringassembly. It is preferred to face the bell end of pipe in thedirection that the pipe is being laid to prevent bedding material from entering the bell during jointing.
When assembling pipe, take care to ensure that workers keephands and clothing clear of joint to prevent injury.
Figure 18 - Proper Line and Grade of Trench
Figure 19- Strapping and Pipe Guidance
22
Join pipe by inserting the spigot into the bell end at as smallof an angle as possible, starting at the top of the pipe, asshow in the detail below.
Note: By doing this you prevent rolling of gasket.
Lower pipe to grade and insert remainder of spigot into thebell. Bring pipe home by pulling the cable or strap as shownin the details below.
Figure 20 - Joining of Pipe
Figure 21 - Bringing Pipe Home
Avoid the use of excavating equipment to push pipe sectionstogether. This can damage the pipe.
Check for proper line and grade. If pipe grade needs to beraised, Hardie® Pipe recommends removing the pipe from thetrench and regrade full length of bedding. Lifting up pipe andshoveling dirt/bedding material under the pipe will leavevoids and is NOT acceptable.
If pipe grade needs to be lowered, Hardie Pipe recommendsremoving pipe from the ditch and correct the grade.
Note: Maintain minimum bedding thickness
Figure 22 - Improper Homing of Pipe
23
Figure 23 - Improperly Bringing Pipe to Line and Grade
24
Once the pipe is set to proper grade, confirm that the gasket hasnot rolled and is not exposed at the joint.
Check with Table 9 of the appendix to confirm the joint gap onthe outside of the pipe is within tolerance.
The remaining backfill material should be placed and com-pacted around the pipe in accordance with project plans andspecifications.
To insure that the pipe does not move when installing thenext section of pipe, uniformly place and compact soil oneach side of the pipe to the specified density to prevent lateraldisplacement of pipe.
Minimum Cover for Construction Loads
Do not allow heavy construction or compaction equipment tocross over culvert or storm sewer pipes until placing andcompacting backfill material to the finished earthwork gradeor to an elevation at least 3-feet above the crown of the pipe,or as noted in project specifications.
Figure 24 - Improperly Seated Gasket
Connecting Hardie® Pipe to Structure/ Manhole
When pipe run comes within one section of the pipe to structure interface, take measurement to determine exactlength of pipe needed to finish the run.
Refer to Table 8 to confirm that the proper sized pipe to structure interface opening has been provided.
Cut length of pipe to the measurement taken above followingthe Field Cutting Hardie® Pipe section of this guide.
Connect pipe to the structure in accordance with engineer’splans and specifications.
Helpful Hint: Hardie ®Pipe outside diameters are smaller than
steel RCP outside diameters allowing for a smaller hole to be
cast into the concrete structure. Consult structure
manufacturer to confirm size of structure opening.
Figure 25 - Pipe to Structure Detail
25
26
Differential settlement between the structure or manhole andthe pipe may result in damage to the pipe. Therefore, it isimportant to install the structure or manhole on a solid foundation to eliminate settlement. When connecting HardiePipe to a structure or manhole, it is necessary to construct auniform bedding over the entire length of the pipe barrel todistribute the load-bearing reaction evenly to the beddingover the full length of the pipe barrel. Suspending the pipeover a void created by the excavation around the structurewhile the pipe is grouted into the side of the structure is notrecommended since uniform support to the pipe is not beingprovided. This lack of support around a structure can result indamage to the pipe. After the structure is set, backfill shouldbe brought up to the invert of the pipe, and then the pipeshould be connected to the structure.
Note: If there is a possibility of differential settlement
between structure and pipe consult with Hardie Pipe.
Field Cutting Hardie® Pipe
Use a cutting device capable of cutting reinforced concreteproducts.
Use appropriate safety precautions when operating saw/bladein accordance with manufacturers recommended practices.
Helpful Hint: For quick results, use a diamond tipped blade to cutpipe when using a powered saw.
1. Mark a cut line on the outside of the pipe.2. Make sure pipe is stable before cutting.3. Cut length of pipe to the cut line marked.4. When cutting a length of pipe, it will be
necessary to roll the pipe to get access to the entire circumference. After rolling make sure pipe is stable before resuming cutting. Hardie Pipe recommends pipe be chocked.
27
Proper safety gear must be worn to protect operator in accordance with applicable safety standards.
Cutting of Hardie® Pipe can produce dust that can be harmfulif exposed to excessive amounts over an extended period oftime. Hardie Pipe recommends that the pipe be cut as followsto help reduce dust exposure levels:
1. When using a powered saw, use saw blades specifically designed for reducing dust generation, such as a low-tooth count blade with polycrystalline diamond-tipped teeth.
2. If using a powered saw, Hardie Pipe recommends using a saw equipped with an effective dust collection or suppression system.
3. Hardie Pipe recommends that cutting occur only in well-ventilated areas, such as open, outdoor environments.
Figure 26 - Cutting Pipe Figure 27 - Improper Cutting(Hammer & Chisel)
28
Hardie® Pipe does not recommend cutting in indoor or otherwise poorly-ventilated areas, does not recommend usinga dry continuous rim diamond-edged blade when using apower saw, and does not recommend dry sweeping of pipedebris.
If exposures exceed the Occupational Safety and HealthAdministration (OSHA) Permissible Exposure Limit (PEL),NIOSH-certified respiratory protection must be worn. If uncertain about the appropriate respiratory protection orexposures, consult a qualified industrial hygienist.
Warning: AVOID BREATHING SILICA DUST. Hardie Pipe
contains silica. Inhalation of respirable silica dust can cause
silicosis, a potentially disabling lung disease, and is known to
the State of California to cause cancer. When drilling, cutting
or abrading Hardie Pipe during installation or handling: (1)
Work outdoors where feasible, otherwise use mechanical
ventilation, (2) Wear a dust mask or, if dust may exceed PEL
use NIOSH approved respirator, (3) Warn others in area. For
further information, refer to Material Safety Data Sheet or
contact manufacturer by calling 1-877-910-3727.
29
Hardie Pipe Warranty
Hardie® Pipe warrants that its goods are free from manufacturing defects for a period of one year. If any of itsgoods are proven to be defective, Hardie Pipe will, at its soleoption, either supply replacement goods or reimburse thebuyer for the purchase price the buyer paid. Whether abuyer's claims are based on negligence, breach of any impliedwarranty, strict liability, or any other theory at law or in equity,this remedy shall be buyer's sole and exclusive remedy.Hardie Pipe is not liable for any indirect, consequential, economic, loss profits, punitive or exemplary damages of anytype, under any circumstances, including those resulting fromany manufacturing defect. Submit claims to Hardie Pipe, inwriting, within thirty (30) days from date of discovery. State orfederal laws may provide the buyer with rights in addition tothose in this warranty that cannot be modified or excluded.
The recommendations in Hardie Pipe literature (e.g.brochures,printed instructions, etc.), or on its website represent goodbuilding practices. However, they are not intended to be anexhaustive statement of all the relevant data, nor are they (or any oral statements made by Hardie Pipe) intended to augment, modify and/or change the terms of this expressedwarranty. The terms of this warranty can only be made byHardie Pipe in writing. Further, there are many factors outsideof Hardie Pipe's control (e.g. quality of workmanship, particular design, detail requirements, etc). Hardie Pipe is neither responsible nor liable for any installation, application,or specification factors or decisions made by the buyer, oranyone or any entity acting on the buyer's behalf, which mayaffect the quality of its goods, the success of any project, orthe suitability of its goods to achieve a particular purpose.
To this extent, Hardie disclaims all other warranties, expressor implied, including any implied warranties of merchantability or fitness for a particular purpose, or anyother implied warranties that may be imposed by virtue of theUniform Commercial Code.
30
Appendix
Hardie® Pipe Field Repair Procedures
If minor damage to Hardie® Pipe occurs during handling orinstallation, repairs can be made in accordance with the following procedures or in accordance with engineer’s plansand specifications.
Standardized methods for repairing Hardie Pipe are presentedto ensure that all surfaces of near contact of the jointed pipesare free from chipped or spalled concrete and other suchdefects. Pipes showing minor manufacturing imperfectionshandling injuries to the bell and spigot, or pipe barrel damagemay be repaired using methods described below.
Case 1 - Cracking or Chipping of the Joint
Cracking or chipping that does not affect the sealing area ofthe joint may be repaired if the affected area meets the following conditions:
The chipping or cracking does not affect the ring groove.
Cracking may not propagate through the joint wall.
The circumferential length of a single area to be repaired shallnot exceed one fourth of the inside diameter of the pipe or thecircumferential length of several areas combined does notexceed one half of the inside diameter of the pipe.
The repair does not reduce the clearance between the bell andspigot sealing surfaces compromising the flexibility of the joint.
31
Procedure
1. Clean the area of all dirt and excess material.
2. Allow the area to dry
3. Apply an epoxy compound suitable for repairing spalledareas on concrete structures as approved by the DOT.
4. Allow epoxy to fully dry
5. Sand and smooth the repaired area to the proper joint specifications
Note: Repair should not be attempted if there is any loss ofmaterial extending into the gasket groove area. If the bell orspigot is beyond repair, cut the damaged section back tosound, solid material and use this undamaged section of pipeto come into or out of a structure.
Case 2 - Puncture Holes
Punctures holes may be repaired if no larger than sizes listedbelow:
The size of the hole is measured after the hole has been cutback to sound material.
There are two approved methods of repair, either by applyinga saddle patch or saddle plug.
Table 4 - Puncture Hole LimitsPipe
Diameter(Inches)
Puncture HoleSize Max.(Inches)
12 4
15 4
18 6
24 6
30 6
36 6
32
Procedure A – Saddle Patch
To apply a saddle patch follow these guidelines:
� Remove damaged material from the affected area and cut back to sound material then sand smooth.
� Measure the hole.
� Using a pipe with an inside diameter as close as possible to the outside diameter of the pipe being repaired, cut a blank saddle approximately 2/3 larger than the hole.
� Clean the saddle and area to be covered of all dirt and debris.
� Apply a DOT approved epoxy resin adhesive for bonding hardened concrete to hardenedconcrete.
� Place the saddle over hole and secure in place while epoxy cures.
Procedure B – Saddle and Plug
To apply a saddle and plug which gives you an internal flushfinish following these guidelines:
� Remove damaged material from the affected area and cut back to sound material then sand smooth.
� Measure the hole.
� From the identical size and class pipe, make a plug approximately 1/4–inch smaller than the hole.
� Using a pipe with an inside diameter as close as possible to the outside diameter of the pipe being repaired, cut a blank saddle approximately 2/3 larger than the hole.
33
� Epoxy the plug to the inside of the saddle using a DOT approved epoxy resin adhesive, for bonding hardened concrete to hardened concrete.
� Clean the saddle and area to be covered of all dirt and debris.
� Make sure the saddle and area to be covered are dry.
� Epoxy around the edges of the plug and fit into hole.
� Secure in place until epoxy cures.
Case 3 - Surface Imperfections
Surface layer roughness may be repaired, providing that thefollowing criteria are met:
The imperfection does not exceed 10% of the pipe wall thickness.
The area to be repaired does not exceed 10% of the total pipesurface area.
Procedure
� Use mechanical grinding equipment. Grind at least 1” past the edges of the unaffected area surrounding the repair.
� Fill area with a coating of a DOT approvedepoxy designed for repairing spalled areas on concrete structures.
� Work should be performed outdoors, wearing and usingproper safety equipment. Inform others in the area of the grinding operation.
34
Case 4 - Gouging
Gouging that does not exceed 20% of the wall thickness maybe repaired. There is no limit to the length of the affectedarea.
Procedure
1. Sand the affected area smooth.
2. Clean all dust and debris from gouged area.
3. Fill gouge with a coating of a DOT approved epoxydesigned for repairing spalled areas on concrete structures.
4. Allow epoxy to cure.
NOTE: Cracking that occurs along the length of the pipeis not permitted to be repaired.
Table 5: Bundling Standards by Diameter & Pipe Class
Hardie Pipe is crated as in the followingdrawings:
90” Dunnage with banding
12” Diameter Pipe
Minimum 84” Fork
Length Required
90” Dunnage with banding
15” Diameter Pipe
Minimum 81” Fork
Length Required
35
36
85” Dunnage with banding
18” Diameter Pipe
90” Dunnage with banding
24” Diameter Pipe
Minimum 73” Fork
Length Required
Minimum 71” Fork
Length Required
37
95” Dunnage with banding
30” Diameter Pipe
80” Dunnage with banding
36” Diameter Pipe
Minimum 87” Fork
Length Required
Minimum 80” Fork
Length Required
Table 6: Pipe Nominal Weight Chart
CLASS AND SIZE COMPARISON
PIPEDIAMETER
(inches)CLASS
HARDIE PIPECONCRETE PIPE
NOMINAL WEIGHTPER FOOT (LBS)
STEEL REINFORCED CONCRETE PIPE
NOMINAL WEIGHTPER FOOT (LBS)
12III
IV
V
26
32
40
120
120
120
15III
IV
V
40
53
63
155
155
155
18III
IV
V
58
72
91
175
175
175
24I
II
III
IV
V
77
87
103
128
161
290
290
290
290
290
30I
II
III
IV
V
120
136
160
200
252
410
410
410
410
410
36I
II
III
IV
V
173
196
231
287
362
563
563
563
563
563
38
Table 7: Shipping Specifications
SHIPPING SPECIFICATIONS
PRODUCTCODE
SIZE(CLASS III)
INSIDEDIAMETER
(IN)
PIPES PERTRUCK
PIPES PER PALLET
FT PER LOAD
(16’ LGTHS)
112500 12” 12.0 60 6 960
115400 15” 15.0 45 5 720
118300 18” 18.0 40 4 640
124300 24” 24.0 24 3 384
130300 30” 30.0 15 3 240
136300 36” 36.0 10 2 160
39
40
HARDIE PIPE ODs
Pipe Diameter Class OD
12”III 13.77
IV 14.18
V 14.70
15”III 17.22
IV 17.73
V 18.37
18”III 20.67
IV 21.27
V 22.05
24”
I 26.72
II 27.05
III 27.56
IV 28.36
V 29.39
30”
I 33.39
II 33.81
III 34.45
IV 35.45
V 36.74
36”
I 40.07
II 40.57
III 41.33
IV 42.54
V 44.09
Table 8: Nominal Pipe ODs
Table 9: Joint Gap Tolerances
HARDIE PIPE GAP ALLOWANCES
PIPEDIAMETER
GAP ALLOWANCE(mm)
GAP ALLOWANCE(in)
12 9 3/8
15 12 1/2
18 12 1/2
24 20 3/4
30 25 1
36 25 1
41
42
Table 10: Color Code of Center Stripe for Pipe Classes
PIPE CLASS CENTER STRIPE COLOR
1 Orange
2 Blue
3 Black
4 Yellow
5 Red
Customer Service: 1-877-910-3727
Customer Service Fax: 1-866-329-3727
Customer Service Email: [email protected]
www.hardiepipe.com
RR
© 2004 James Hardie Building Products, Inc. All Rights Reserved. Printed in the U.S.A.
™,® and © denote trademarks and are copyrights owned by James Hardie Research Pty Limited ACN 066 114 092.
With all of the rain Clark County receives, managing rainwater runoff can be a
challenge. Installing and/or properly maintaining gutters on your house and outbuildings provides a simple and effective measure of collecting and
diverting rainwater, reducing mud and keeping clean water clean (see the fact sheet
Managing Roof Runoff).
What can be done with all of the water collected in those gutters? And how do you manage rain that lands on your pastures and other areas? Water flowing across pastures, turnouts and dry lots, arenas and other areas can pick up particles of sediment and manure. Nutrients attach to sediment particles and can be transported to nearby waterbodies where they can negatively impact stream health and fish and wildlife. Runoff may also cause erosion and create mud, which can affect the health of your animals and your land. Runoff collecting around foundations of barns and other buildings causes significant damage over time. Several methods are available to collect and divert rainwater before it reaches pastures, turnouts and buildings reduces mud and standing water, and limits erosion and property damage including french drains, berms, grassy swales or dry wells.
French Drains
As illustrated in Figure 1, french drains intercept water flowing across a slope. They are shallow trenches lined with weed cloth or geotextile fabric, with a perforated plastic pipe surrounded by gravel. The weed cloth is wrapped over the top of the gravel and then covered with soil. The weed cloth prevents soil from filling in the spaces between gravel, maintaining water flow through the gravel. To facilitate water flow, the trench should be sloped between 0.5% and 1%. For example, for every 100 feet in distance, a one foot drop in elevation would provide a 1% slope.
French drains can be used to collect runoff flowing down a slope or from a gutter system
and divert the water around a feature such as a building, turnout, driveway or arena. Rainwater from a single roof can be collected in gutters and the buried downspouts connected to a
Keeping Clean Water Clean and Reducing Mud
Improving Drainage
Small Acr eage P rogram
Figure 1: Cross Section of Typcial French Drain
(Doug Stienbarger, 1995)
Aggregate fill
Existing Ground
Geotextile or Weed Cloth
4 inch perforated PVC / Corrugate Plastic drain pipe
1
Keeping Clean Water Clean and Reducing Mud - Improving Drainage
french drain (Figure 2). A T-shaped pipe can be placed at the end of the french drain outlet to slow the speed of the water, and spread it out over a larger area (Figure 3).
Small Acr eage P rogram 2
GutterRafter
Downspout support
Downspout
Downspout adaptor
Underground outlet90 Degree elbow
(Doug Stienbarger, 1996)
Roof
Figure 2: Underground Gutter Outlet
Cross Section (front) Cross Section (side)
Perforated CPP for dissapating energy of rainwater Geotextile or weed cloth
Dispersion pit filled with 2 inch minus gravel fill lined with geotextile or weed cloth
Perforated CPP for dissapating energy of rainwater
Solid corrugated plastic pipe from gutters/french drain
“T” connectionEnd cap
6”
8”
3”Min. 3’
14”
6”20”
6”
(Doug Stienbarger, 1995)
Figure 3. T-shaped Buried Outlet
Plan View
Solid corrugated plastic pipe (CCP) from gutters/french drain
Perforated CPP for dissapating energy of rainwater
End cap
Min. 3’3”
20”
Geotextile or weed cloth
6”
French drains can also be used to collect water draining from adjacent properties and direct it on your property where it will not do any damage. French drains work best if they are not within the groundwater table. Heavy machinery and livestock should be kept off the french drain. They can
compact the soil, crush the drainage pipe and damage the drain, thereby blocking water flow and requiring repairs and possibly replacement.
Berms
Berms are low mounds of vegetated soil two to six inches in height. Berms direct and slow the speed of runoff, allowing it a greater chance to infiltrate and filter out sediments, nutrients and other materials in the water. Berms can also be used to divert water around a building, or at the base of a slope to direct runoff around an area such as a livestock turnout. Diverting this “run-on” water around livestock turnouts can greatly reduce mud in these areas.
Keeping Clean Water Clean and Reducing Mud - Improving Drainage 3
Grassy swales
Swales are shallow, gently sloped vegetated ditches that capture runoff and transport it away from heavy use areas. Swales are commonly planted with grass, which slows down runoff and facilitates infiltration and removal of sediment and other particles. Swales can be easily incorporated into the landscape on your property, particularly if there is already a low lying area on your property. Swales are often less expensive to install than some underground drainage systems. Swales should be designed to hold water for no more than 48 to 72 hours to reduce habitat for mosquitoes. If standing water is expected for longer periods of time, wetland plants such as rushes (Juncus spp.), cattails (Typha spp.) or sedges (Carex spp.) can be planted.
Maintenance should occur when the soil is not saturated to prevent compaction, which can limit infiltration of runoff. Cuttings should be removed to prevent smothering of the vegetation. Grazing of these areas may be possible, but should be controlled to maintain healthy vegetation. Do not graze during initial vegetation establishment, when the soil is wet or during reseeding of bare areas. Grass height should be maintained at no less than 3 to 4 inches tall. Shorter grass does not provide adequate erosion protection. Bare or eroded spots should be repaired and reseeded. The swale should not be used as a track or roadway. Frequent traffic may damage the swale and create ruts, which can concentrate water flow and eventually result in erosion and the formation of gulleys.
Dry wells
Directing downspouts into drywells can help facilitate infiltration of water into the surrounding soil and prevent it from picking up sediment from the surface. A dry well is a small pit lined with geotextile fabric or weed cloth and filled with 1½” to 3” gravel. Dry wells are best used to collect runoff from a small area with little or no sediment or pollutants, such as stormwater from a roof. Soils surrounding the dry well should be sufficiently permeable to allow adequate infiltration of the runoff. The dry well should be designed to completely drain the water volume into the soil within 48 hours of the rain event. An overflow may be needed to handle large amounts of runoff. Dry wells are relatively small and because they are underground, do not take up much space. They can be installed out of the way, provided the dry well can be easily accessed for maintenance.
Locate dry wells at least 10 feet from building foundations and at least 75 feet from wells, septic systems and surface water bodies.
Permits
Moving soil around on your property to build a french drain, drywell, berm or swale may require a grading permit if more than 50 cubic yards or more of material is moved. More information is available in the fact sheet Frequently Asked Questions: What Can You Do On Your Land? Before beginning any
work, contact Clark County Community Development at 360-397-2375 x 4347.
All of these drainage structures can help you manage runoff on your property, reduce mud and erosion, allow runoff water to infiltrate and recharge groundwater and maintain healthy water quality in Clark County surface waters.
Small Acr eage P rogram
The Small Acreage Program is sponsored in partnership by WSU Extension Clark County, the Clark County Clean
Water Program, and the Clark Conservation District.
Extension programs are available to all without discrimination. Report evidence of noncompliance to your local Extension office.
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Small Acr eage P rogram
Keeping Clean Water Clean and Reducing Mud - Improving Drainage
For additional information on managing roof runoff and drainage, contact:
Washington State UniversityClark County Extension11104 NE 149th Street C 100Brush Prairie WA 98606360-397-6060 extension 7720http://clark.wsu.edu/
Clark Conservation District11104 NE 149th Street C 400Brush Prairie WA 98606360-883-1987 extension 110http://clark.scc.wa.gov/
USDA Natural Resource Conservation Service11104 NE 149th Street C 400Brush Prairie WA 98606360-883-1987 extension 3http://www.wa.nrcs.usda.gov/
Sources:
Alameda Countywide Clean Water Program (ACCWP). Grassy Swales Fact Sheet. From: ACCWP Catalog of Control Measures. n.d., 4 pp. http://www.oaklandpw.com/creeks/pdf/Grassy_Swales.pdf
Alberta Agriculture, Food and Rural Development. Grassed Waterway Construction. Agdex # 573-6. n.d., 3 pp. http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex795/$file/573-6.pdf?OpenElement
Connecticut Bureau of Water Management. Dry Wells. Connecticut Stormwater Quality Manual. 2004, 4 pp. http://dep.state.ct.us/wtr/stormwater/manual/CH11_DW_S-5.pdf
Houston Landscape Images. Grading and Drainage Work. n.d., 4 pp. http://www.houstonlandscape.com/Drainage.htm
McVay, K.A., G.M. Powell and R. Lamond. Maintaining Grass Waterways. Kansas State University, MF-1064. April 2004, 3 pp. http://www.oznet.ksu.edu/library/crpsl2/mf1064.pdf
Pfost, D.L. and L. Caldwell. Maintaining Grassed Waterways. University of Missouri Extension, G1504. October 1999, 3 pp. http://muextension.missouri.edu/explore/agguides/agengin/g01504.htm
Adapted by Erin Harwood, WSU Clark County Extension (September 2005).