PROOF PointsPROVEN TECHNIQUES, TIPS & UPDATES

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ROOF AND PAVEMENT CONSULTANTS

1 The Many Purposes of Taking Core Samples in Roofing

4 Advantages of Diamond Grinding Concrete Pavement Restoration

6 Technical Update: ASCE 7-16 Wind Design Standard Forthingcoming

7 Benchmark’s Newest Professional Engineer - Andrew Reynolds, P.E.

8 2017 Roof & Pavement Management Seminar

Oneofthefirstthingsmostroofingprofessionals learn is how to take a core sample or core cut. Core sampling is a destructive test that involves the cutting and removal of roofinglayersuntilastructuraldeckis reached. There are many reasons for taking core samples, most re-volvearoundidentifyingtheroofingmaterials present within a particular roof assembly. The information gathered about the roof system can then be used for estimating, diagnostic, and/or design purposes.

Cutting Methods

As there are different purposes for taking core samples, which we will discuss shortly, there are different methods for cutting cores. One method of taking a core sample is with a special tool developed by the Cold Regions Research Engineering Laboratory, called a CRREL cutter. This tool consists of a 12” long, 2” diameter pipe. One end has saw teeth cut into the pipe, the other has a place to insert a steel rod. The CRREL cutter saws a 2” diameter hole in the roof. The “core” can be pushed out of the pipe and its components examined. The CRREL cutter is fairly efficient,cutsanice,neathole(that is easy to patch), and the time involved in cutting is fairly short. The

negatives to this method of cutting are that sometimes the 2” diameter hole is not large enough to allow forspecificobservationsandtheCRREL cutter tends to compress the insulation (particularly plastic foam) layers. It is also limited to a depth of about8”,whichisnormallysuffi-cient, but can leave you short on roofs with deep tapered insulation systems, for example.

Other methods of core sampling include cutting with an ax, knife and/or insulation saw, or with a reciprocating saw. Cutting with an ax is quick, but often causes damage to the roof layers being evaluated resulting in conditions or construction data being mashed and not as useful.

Cutting with a sharp knife provides the inspector with an opportunity toexaminethetoplayerofroofingmembrane, but cut depth is limited. Using a knife to cut through the roof membrane, and then an insulation knife or saw to cut through the subsequent layers, allows for better examinationoftheroofinglayers.Cutting with a knife/saw combina-tion is useful for cutting samples of 4” to 12” square. Larger samples can be done, but takes a consider-able amount of time.

The Many Purposes of Taking Core Samples in RoofingBy Jeff Evans, RRC

MARCH 2017 | VOLUME 86

continued on page 2

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PROOF Points

Cutting with a reciprocating saw makes short work of core sampling and does so with minimal distur-bance of the various roof layers. It also is the best method if larger samples are desired.

Purposes of Core Sampling

1. Material Identification Whether one is taking core samples for the purpose of evaluation or design, one of the primary purposes is material identification.Theinspectorobserves and documents the composition of the roof mem-brane, cover board, insulation, vapor/air retarder, thermal barrier and roof deck layers, thicknesses, and method of attachment for each layer. With multi-ply bitumen roof systems, the type of bitumen and number of plies can often be determined through core sampling. With single-ply membranes, particularly ther-moplastic, the color or markings

on the underside of the roof membrane can sometimes provide approximate age of the roof membrane. The method attachments of the various membrane and insulation layers can be useful knowledge to have when devising repair and replacement recommenda-tions. For example, whether the existing insulation can be salvaged and re-used during reroofingmaydependonhoweach layer is attached. Core sampling provides valuable information to assist in estimating the cost of a roof replacement. Knowing the roof thickness helps determine the volume of demolition materials; and therefore, estimates the number of trash containers required. Knowing how a roof assembly is attached helps esti-mate how much effort removal will entail. Demolition labor and refuse hauling costs can total 25 percentofareroofingprojectbudget.

2. Roof Slope Identification The slope or pitch in any roof can be the result of several different methods. Generally in newer buildings, the roof structure is sloped to drains or scuppers, which are placed at low points in the structural deck. Poured-in-place deck materials, such as lightweight insulating concrete, are sometimes used toprovideslopeonaflatstructural deck. Finally, tapered insulation may have been used tocreateslopeontopofaflatstructural deck. Particularlywithreroofingdesign, it is imperative to under-stand what element provides slope, structure, topping layer or tapered insulation. Core samples can be used to identify what element is providing slope. If the roof deck is sloped, then multiple core samples taken at various locations across the roof should show the same roof composi-tion and thickness. If lightweight concrete provides slope, then core sampling would allow identifying the thickness at ridges and drains, helping the inspector to under-stand how the slope is provided. Similarly, core samples can help definetaperedinsulationlay-outs, and minimum/maximum thicknesses, for later use.

3. Diagnostic Core Sampling Core sampling is a very useful tool to help diagnose whether

MARCH 2017 | VOLUME 86

The Many Purposes of Taking Core Samples in Roofing continued

CORE SAMPLING REVEALED AN IMPROPER TYPE OF INSULATION FACER FOR THIS ADHERED EPDM APPLICATION.

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or why a particular roof defect may exist, such as blistering in a multi-ply asphalt roof, loss of roof adhesion (blow-off), hail damage, or suspected wet insulation. Core sampling is the surest method of verifying presence andlocationofwetroofingcomponents when conducted at the conclusion of an infrared or nuclear moisture detection scan. Core sampling is also prescribed to identify why a roof failed inafielduplifttest,suchasthose required by FM Global in hurricane prone zones (FM Loss Prevention Data Sheet 1-52).

4. Hazardous Materials Identification Core sampling is required when conducting testing for asbestos contentinroofingmaterials.Testing is often conducted on allroofinglayersincludingroofmembrane, insulation and various barrier layers. Identifying the existence of phenolic foam insulation during core sampling is very important information as this material can cause greatly accelerated corrosion on ferrous materials, such as steel roof decking. Once phenolic insulation is identifiedasbeingpresent,larger cores may be taken to examine whether such corrosion is observed.

5. Roof Design Information It is quite infrequent that roofs are constructed exactly as originally shown in architec-

tural drawings, even “as-built” drawings. In addition, changes occur between the original building construction and the present. Roofs are often recovered or replaced multiple times during the service life of a building, so original building drawingsmaynotreflectthose“updates.” An important example that comes to mind is when core

samples reveal 5/8” gypsum board layer placed directly overasteeldeck.This“find”isa clue that the existing roof was designedtomeetaspecificfireresistance rating. Fire resistive ratings are often required over places of public assembly, and fireresistiveroofconstructionsprovideoccupantssufficienttimetoescapeinafire.Re-roofingdesignshouldseektomatchthefireresistancerating,an effort that may take some research. Coresamplingadjacenttoperimeter edge conditions can provide a roof designer with helpful information such as the height, orientation, and

condition of perimeter wood blocking. A roof designer can then decide whether the blocking can be re-used or whether it needs to be removed and replaced. Knowing whether parapet walls were sheathed with plywood or gypsum board is also good information, as existing gypsum board is often damaged during roof tear-off and may need to be replaced, whereas plywood is typically re-usable.

Curiosity Makes for Good Roof Consulting

A good roof consultant needs to have a broad level of experience and knowledge for sure, and it helps to have some wisdom. But I think the difference maker is curiosity. A roof consultant doing roof evaluations or gathering informationforreroofingdesignwill be well served to be curious.

I have cored through roofs with multiple distinct roof systems only tofindthicklayersofslopedfillmaterial, frozen insulation, or hidden electrical conduit - any of which could have tripped me up and cre-ated certain heartache once under construction. Having a curious mind and the energy to take more core samples will make life easier for the roofconsultant,roofingcontractor,and owner alike.

When a roof consultant or contrac-tor shows the initiative to take core samples, they are exercising due care and diligence, and perhaps - curiosity.

CORROSION OF THE TYPE A STEEL DECKING WAS DISCOVERED AT THIS CORE SAMPLE.

PROOF Points

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Diamond grinding is a concrete pavement restoration process that renews a worn or slightly irregular surface. Diamond grinding can potentially remove or reduce some pavementdeficienciessuchasjointfaults resulting from minor pave-ment settlement, worn pavement from wheel rutting, warped slabs, and a rough surface texture.

Diamond grinding pavement establishes a smoother surface with a better ride quality. Diamond grinding is a procedure where a machine (pictured above) powers a rotating cutting head across the pavement surface in the direction the machine travels. The grinding head consists of a series of closely spaced, diamond-tipped saw blades and spacers that form the cutting head. The grinding head is typically 3’ to 4’ wide, and 12” to 18” in diameter, and consists of 50 to 60 saw blades per foot of drumhead length. The desired surface texture is a result of the number of blades, the thickness of the spacers, and the machine speed.Thesevariablesareproject

specificdependingontheresulttheowner wishes to have and what the restoration is to achieve.

Theoperatoradjuststhedepthofthe grinding to achieve the desired results, but it is generally a half-inch to a quarter-inch in depth. A vacuum system is contained on the machine to pick up the water that is used to cool the cutting head and the slurry produced during the grinding. The slurry is then either dischargedadjacenttothepave-ment being ground or pumped into a tanker and taken off site to a proper disposal location.

Advantages

While not raising the pavement’s elevation, diamond grinding results in improved ride quality, noise reduction, and increased friction resistance. Decreasing the pavement irregularities restores ride quality, whether the irregularities are bumps or low areas in the pavement. Irregularities can be the result of surface wear, construction damage, environmental effects, pri-or pavement repairs or settlement.

Pavements that have irregularities in the commercial or industrial sector affect the ability of the facility to safely transfer goods and products byforktruck,palletjacks,spottervehicles or over the road haulers. Although noise reduction and increased friction resistance are not typicalbenefitsthatacommercialor industrial customer is looking for, thesearedesiredbenefitsformanyhighwayprojects.

Many sites are in a condition where the pavement grades cannot be raised with an asphalt pavement overlay because of drainage concernsorfixeddockandloadingzone heights. Diamond grinding will typically remove only a quarter-inch in pavement height, thereby maintaining the existing drainage flowandrequiredfixedheightsattruck docks and loading zones.

Requirements

Not all concrete pavements are candidates for pavement resto-ration by diamond grinding. When considering diamond grinding, the conditions to study would include pavement surfaces with weak supporting soils and/or poor concrete materials, as well as pavements requiring a lot of repairs or containing high reinforcing steel in the slabs.

The pavement must have a good overall structural integrity, stable base and subbase materials to pro-duce the desired results. Pavement irregularities such as scaling, spall-ing, and certain types of cracking should be carefully evaluated when considering diamond grinding.

Typically, the grinding operation should not encounter the reinforc-

Advantages of Diamond Grinding Concrete Pavement RestorationSave time, money and the environment on your next pavement rehabilitation project.By Daniel E. Wilson, P.E.

MARCH 2017 | VOLUME 86

IS YOUR CONCRETE PAVEMENT SHOWING SIGNS OF DISTRESS? IT IS POSSIBLE TO USE A DIAMOND GRINDING PROCESS TO RENEW THE SURFACE.

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ing steel in the pavement due to the limited grinding depth on a typicalproject.Thegrindingopera-tion may have to skip over sections if reinforcing steel is found so as to not risk damaging the cutting head.

Considerations

When existing conditions won’t allow for an asphalt overlay, a concrete pavement restoration process is the answer. Often, an overlay of asphalt on a concrete surface is not the best solution. Factors to consider are the poten-tial for freeze/thaw cycles that can degrade the serviceability of the overlay reducing its life span, the stability of the concrete surface, concretejointconditions,andthesurface drainage slope.

The climate in many parts of the country is a deciding factor on whether asphalt is the right answer for concrete pavement rehabili-tation. The effects of moisture and freeze/thaw cycles can cause reflectivecracking,delamination,andjointdeterioration.Concretepavementwithwiderjointsthathave not been maintained through ajointsealingmaintenancepro-gram will cause a higher degree of reflectivecrackingatafasterrateleading to surface delamination. In a milder climate that is typical ofthesouthernstates,reflectivecracking is less of a concern.

Many times, designs of concrete pavements have a lower degree of surface slope than a corresponding asphalt surface. The lower surface slopes may not have the desired surfaceflowwithanasphaltoverlay, making diamond grinding a good choice. If the pavement construction includes a curb and gutter, and the surface drainage is towards the curbs, diamond grind-ing would be a good choice.

Restoration In Action

Oneofourrecentprojectsinvolvedconcrete pavement restoration using diamond grinding. The facility was a large warehouse and distri-butioncenter.Theprojectincluded13,000 square yards of roadway and dock pavement over a 1,800-foot long section of the warehouse. The pavement had an asphalt overlay installed several years ago, which was showing signs of distress with large areas of delamination andreflectivecracking.

This site was a perfect candidate for restoration because:

• The pavement had valley drainage towards the main roadway.

• Curbs on the perimeter had pavement slopes towards the roadway center.

• The older overlay had affected the trailer heights at the loading docks.

• In the areas of delamination, the concrete pavement appeared sound and stable.

• The surface of the concrete pavement installed in the 1970s appeared to be in fair condi-tion.

• The trailer landing gear was wearing through the asphalt surface to the concrete below.

• Full closure of many of the docksandtheadjacentroad-way was not an option.

Evaluation of pavement cores determined the existing asphalt and pavement thicknesses and

the composition and stability of the base and subbase. The processes involved several phases in order to have the least possible amount of impact on the owner’s operations.

The process involved:

• Milling existing asphalt off the surface to expose original concrete pavement.

• Determining the limits of the pavementandjointrepairs.

• Adjustingdrainagestructurestothe new pavement elevation.

• Diamond grinding the pave-ment.

• Pavement marking.

• Joint and cracksealing.

Milling and diamond grinding were able to re-establish the properdrainageprofile,drainagesurfaceflow,andprovideabetterride quality for trucks and spotter vehicles.Thefinishedsurfacealsoallows the owner to begin a mainte-nanceprogramonthejointsintheconcrete pavement that are now uncovered. A timely and consistent maintenance program is essential to any pavement to prolong service life.

TEXTURE OF THE SURFACE AFTER DIAMOND GRINDING PROCESS IS COMPLETED.

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PROOF Points

Technical Updates: ASCE 7-16 Wind Design Standard Forthcoming By Tom Irvine, RRC, CDT

The International Building Code (IBC) mandates that a roof’s wind uplift resistance be designed to satisfy the requirements of ASCE-7. ASCE-7 - Minimum Design Loads for Buildings and Other Structures is published by the American Society of Civil Engineers. ASCE 7-10 is the last published revision, and is refer-enced in the 2015 IBC.

ASCE reports that the latest revision to the standard, ASCE 7-16, is slated for release in early 2017. The Gov-ernmental members of the Inter-national Code Council (ICC) have voted to adopt the 7-16 standard within the current 2018 I-Code revi-sion cycle, and it is widely predicted that full approval and adoption will follow. Subsequent state adoptions of the 2018 I-Codes will trigger the needforroofingprofessionalstousethe 7-16 standard, likely beginning in 2019.

There are several notable changes to ASCE 7 being discussed in the roofingindustry,whicharegenerallybased on reviews and commen-tary on the draft 2016 standard. Althoughthefinalstandardhasnotbeen published as of this writing, the following notable changes are anticipated:

• ASCE 7-10 wind maps and associated wind speeds will be updated in 7-16. ASCE reports that wind speeds will be reduced for much of the U.S. where located outside of hurricane-prone regions. A separate wind speed map will be included for Occupancy Category IV buildings, where previously Category III and IV buildings were addressed on a

combined map. Special wind regionswillalsoreceiveclarifi-cation, including Hawaii.

• In ASCE 7-10 and earlier versions, widths of perimeter, corner, and ridge attachment enhancement zones for low slope roofs are calculated as 0.1 times the roof’s least horizontal dimension, or 0.4 times the build-ing height - whichever is less, but not less than either 4 percent of the least horizontal dimension or 3’. In ASCE 7-16, calculating zone widths using 0.1 times the roof’s least horizontal dimension will no longer be allowed, and calculations must be based on 0.4 times the building height. This change will result in larger enhancement zones for many roofs, compared to the dimen-sions required under 7-10. For example, a 50’W x 200’L x 40’H roof would require 16’ wide perimeter zones and 16’ x 16’ corner zones under 7-16, as opposed to 5’ perimeters and 5’ x 5’ corners under 7-10.

• Externalpressurecoefficientsfor components and cladding have increased; however, the finalpressureswillbeoffsetbya reduction in the design wind speeds over much of the U.S. In hurricane prone regions, wind speeds were not reduced while pressurecoefficientsstillreceivethe global increases. This will resultinsignificantincreasesin design pressures in hurri-cane-prone regions.

• In ASCE 7-10 and earlier versions, there is one basic enhancement zone layout for

low slope roofs with variations outlined for roofs higher than 60’, where parapet wall heights exceed 3’, and at perimeters and corners of monoslope roofs. In 7-16, there will reportedly be four model enhancement zone layouts for low slope roofs, which will require selection based on the relationship between the least horizontal roof dimension and the roof’s height. The zone dimensions will need to be calculated for the selected layout as prescribed by the standard.

• ASCE 7-16 will introduce a fourth enhancement zone for roof attachment, in addition to the traditional industry standard pe-rimeter, corner, and ridge zones used in 7-10 and earlier versions. The new zone will reportedly apply to very large buildings.

• Hip and gable roofs will be sep-arated under 7-16, with pressure coefficientsbasedonrevisedslope criteria in some cases.

• In the new standard, design requirements for rooftop pho-tovoltaic (PV) equipment will beaddressedforthefirsttimeunder ASCE-7.

• A ground elevation factor is added under ASCE 7-16, which adjustscalculationstoaccountfor variations in air densities at different altitudes.

OnceASCEreleasesthefinalstandard,amoredefinitiveanalysisof the changes and impacts on roof design and construction will be possible. Benchmark will provide

MARCH 2017 | VOLUME 86

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furtherinformationastheroofingindustry reacts and adapts to the changes.

Building the roof “on paper” will no doubt become more complex for the design community. It will

also be increasingly important to communicate the application requirementstotheroofingtech-nicians and monitor their work for compliance with the contract documents. There will be a learning curveasroofingcontractorsadapt

Technical Updates: ASCE 7-16 Wind Design Standard Forthcoming continued to new and larger enhancement zones, with potentially different layouts than in years past.

Afterjoiningthe Bench-mark team in 2010 as a summer intern, Andrew’s experi-ence and expertise continues to develop as

hehonesinontheroofingindustry.Throughout Andrew’s initial summer internships, he gradually expanded his repertoire from reading NRCA manuals and taking notes, to folding drawings for the drafting department, and occasionally boarding a plane to assist with surveys as he sketched drawings and performed core cuts.

As he returned to Benchmark throughout subsequent summer breaks, Andrew’s level of involve-ment continued to expand as he shadowed numerous senior consultants on complicated survey work and assisted with full-time projectmanagementtodeepenhisknowledgeofvariousroofingsystems. His survey work often led him to pulp and paper mills, allowing him to further expand his apprehension of this challenging and unique environment!

Following graduation in 2012, Andrewofficiallybecameamember of the Benchmark roof

consultingteam.Startingasafieldconsultant and overseeing the proper installation of roof systems allowed him to develop a deeper knowledge and appreciation for the way a roof is properly construct-ed.

In 2014, Andrew was promoted to staff consultant where his skills allowed him to focus more on completing roof evaluations and developing recommendations andassociatedfive-yearbudgetforecasts for Benchmark’s clients located through the country. Addi-tionally, Andrew began developing roofreplacementspecificationsunder the careful guidance of Benchmark’s senior design team.

Throughout Andrew’s diverse involvement with the roof consulting industry, dedicated training from his peers, and countless hours of study, Andrew ultimately sat for and passed the professional engineering exam in October 2016. Andrew adds, “obtaining my P.E. was one ofthemostdifficultchallengesthatI have come across. I was by no means an exceptional student, nor am I a good test taker. I studied for almost a year for the test, taking multiple review courses, and probably doing close to 600 to 700 practice problems in preparation for the exam. To have that behind me means a lot, because I couldn’t imagine having to do it all over again! Also, it has been nice having

my weeknights and weekends back!”

In addition to Andrew obtaining his P.E., he has also recently become a member of Benchmark’s Tech-nical Committee. Along with his role on the Committee, he remains committed to being more involved withthetechnicalsideofthejobsuch as building code require-ments, ASCE 7 updates, changes in manufacturer’s materials or requirements, etc.

Amongst the many things that captured Andrew’s interests about Benchmark, one of the things he has grown to appreciate is the level of customer intimacy that develops while assisting a client, adding “now that I am involved mainlyinspecificationandsurveywork,Ireallyenjoytherelationshipbuilding with clients and our con-tacts at different facilities. Even the smallest thing like designing a difficultdetailonajobandseeingit installed successfully can be very enjoyable.”

Benchmark is extremely proud of the dedication Andrew contin-ues to show the roof consulting industry, our clients, and the rest of the Benchmark team. We congratulatehimonajobwelldone in successfully obtaining his P.E. license, and look forward to the future!

Benchmark’s Newest Professional Engineer Congratulations to Andrew Reynolds, P.E.

ANDREW REYNOLDS, P.E. STAFF CONSULTANT

Proof Points is a publication of Benchmark, Inc. We welcome your feedback on the topics presented in Proof Points. To be included on Proof Points’ mailing list, email us at proofpoints@benchmark-inc.com

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Benchmark’s Roof and Pavement Management Seminarwillbenefitthoseinvolved in the selection, design, resto-ration and maintenance of roof and pavement assets. During the seminar, attendees will learn practical strategies to make informed decisions and extend the life of these assets by reducing risk, controlling costs and ensuring quality.

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Benchmark, Inc. Roof & Pavement Management Seminar