Sinking in Concrete

Calculating materials for a concrete job.

Trend

• Many people choose to have concrete work done around their house as they feel it will last longer and look nicer. This is a growing trend in the industry and in order to perform these jobs most people will ask their contractor for a quote (estimate) before the process begins.

Quotes/Estimates

• In order to make an estimate for your client you are going to have to calculate the amount of materials needed.

• Once you know how much material you need you are going to have find (or know) the current prices of the materials so you can total the price.

• After you know the material cost, then you can add your labour charges.

Situation

• Mr. and Mrs. Johansen have hired you for some of their exterior renovation projects this summer.

• Look at their house plan (open in word)

• This is what they would like:

• Mr. Johansen would like a double width driveway in concrete with a curved sidewalk leading to the stairs at the front porch.

• Their brother is going to build a deck for them out of the back patio door, but they would like you to pour the concrete for the deck piers.

• Mrs. Johansen would like a walkway, also out of concrete leading from the front door to the back deck. (It does not have to be curved)

• They have a fire pit in the backyard and would like a cement walkway around the pit to stop sparks from burning their grass.

• Mrs. Johansen also thought it would be nice if a cement curb was installed beside the garage leading to the front door so she can plant her famous rose bushes.

• She would also like a garden in front of bedroom three in between the sidewalk and the house that wraps around to meet up with the wall that sticks out from the bathroom.

Break it down!

• We will need to break down this job into several parts to make the estimate more manageable.

• We have six components:– Driveway– Sidewalks– Garden edging– Fire pit– Deck Piers

Extra info

• Before we begin there is some additional information that you need to know! Such as:– What materials are required?– How much do the materials cost?– What specifications would the owner like in

regards to their projects?

Let’s look at one project at a time!

Talk to the owner

• To determine exactly what the customer would like you ask them some specific questions about their projects.

• Look at the driveway, what do you need to know?

• We need to know how wide they would like it.

• Mr. Johansen says “Make it even with the garage”

Driveway

• The driveway is a rectangular slab so we will need to use the volume formula to determine our material allotment.

• V=l*w*h• The length is 22’6”, width is 21’3” and the

height depends on the materials, we will need a 12” base of B-grade gravel, a 6” base of A-grade gravel and a 5” slab of concrete on top.

Convert Measurements

• We can not calculate the volume of something in two different measurements. Since the majority of materials are measured by the foot we need to convert all of our measurements to feet.

• Length – 22’6”

• The inches need to be converted to feet!

• Remember there are 12” in 1’ so:

in this case divide 6 by 12

=0.5’

• The total length is 22.5’

• Try converting the width and the height (thickness)

inft

x

12

6

1

• Width:

3 divided by 12 = 0.25

• So the width is 21.25’

• Height (gravel):– 6” has already been calculated to 0.5’

Concrete:

5 divided by 12 = 0.42’

inft

x

12

3

1

inft

x

12

5

1

Calculate the amount

• Now we can calculate the volume of the materials:

• Gravel (B-grade): V=l*w*h = 22.5*21.25*1 = 478.13 cubic feet• Gravel (A-grade): V=l*w*h

= 22.5*21.25*0.5 = 239.06 cubic feet– Try the concrete!

• Concrete: V=l*w*h

= 22.5*21.25*0.42

=200.81 cubic feet

• Are there any other materials needed to pour a driveway?

• YES! You need wood to frame the job AND a wire mesh (rebar) to keep the slap solid and together.

More Calculations!

• The wire mesh is a single layer that will spread across the driveway inbetween the gravel and the concrete. To calculate the amount we will need to know the area of the top surface.

• A=l*w

• A=22.5*21.25

= 478.13 square feet

• The framing wood will go around the outside of the job. You will use ½” plywood that will be cut into 6” strips.

• Because the wood goes AROUND the job, we need to find the perimeter!

• P=2l+2w

= 2(22.5)+2(21.25)

= 45 + 42.5

= 87.5’

Recap

Gravel

B-grade

Gravel

A-grade

Concrete Rebar Wood

Driveway 478.13 cubic feet

239.06 cubic feet

200.81 cubic feet

478.13 square feet

87.5’

B-grade A-grade

Concrete Rebar Wood

How sold? Cubic Yard

Cubic Yard

Cubic meter

4x8 sheet

4x8 sheet

Unit price? $6.00 $7.00 $200 $14.45 $37.00

# needed

Total of each item: (row 2 times row 3)

Convert measurements to match how they are sold!

• A sheet of plywood is 8x4, if we cut this into 6” strips you will get 8 strips that are 8’ long.

• 8’ strips * 8strips = 64’ in one sheet of plywood.

• Since we need 87.5’ we can divide this by 8 to find the number of strips we will need!

• 87.5/8 = 10.9 round up to 11

• Since 8 come in one sheet we will need approximatly 1 ½ sheets of plywood for the driveway.

• Since we can not buy ½ we will need 2

Rebar cost

• A 9 gage 6” grid rebar is sold as a 4x8 sheet

• A=4*8 = 32 square feet

• We need 478.13 so divide to find out how many sheets!

• 478.13/32 = 14.94 or approx 15

Gravel Cost

• Gravel is sold in cubic yards. Since 1cubic foot = 0.037 cubic yards we need to convert!

• B- Grade

• Now we multiply

478.13*.037 = 17.69

• We will need to order 18 cubic yards

cuyd

x

cuft 037.1

13.478

• A-Grade

• 239.06*0.037 = 8.85

• Since we can not order .85 we will need 9 cubic yards.

cuyd

x

cuft 037.1

06.239

Concrete Cost

• Concrete is sold by cubic meters• 1 cubic meter = 1.82 cubic yards• We need to conver to cubic yards first,

then to cubic meters!

• 200.81 * 0.037 = 7.43 cubic yards

cuyd

x

cuft 037.1

81.200

• Now convert cubic yards to cubic meters:

• 7.43 * 1.82 = 13.52

• We will need to order 14 cubic meters

cumt

x

cuyd

cuyd

82.11

43.7

B-grade

A-grade

Concrete Rebar Wood

How sold?

Cubic Yard

Cubic Yard

Cubic meter

4x8 sheet

4x8 sheet

Unit price?

$6.00 $7.00 $200 $14.45 $37.00

# needed 18 9 14 15 2

Total of each item: (row 2 times row 3)

$108 $63 $2800 $216.75 $74.00

Price it out!

• We can price this job individually or add it up at the end. We will do both to see which one is better!

Total Cost

• Gravel (B-grade): $108.00

• Gravel (A-grade): $63.00

• Concrete: $2800

• Rebar: $216.75

• Wood: $74.00

• Total: $3261.75

+ tax (multiply by 1.13) = $3685.78