Sinking in Concrete

Day 2 - Sidewalks

Extra Info

• Now you are ready to move on to the sidewalks.

• There are two sidewalks in this job– From driveway to porch– From porch to back of house What do you need to know?

How wide to make the sidewalks Where the gardens will be

Talk to the Owner

• Mr. Johansen would like the sidewalk to be 4’ wide.

• Mrs. Johansen would like a 2’ wide flower bed from the porch wrapping around the side of the house to meet up with the bathroom wall.

• Add this to your house plan. (open house plan day 2 in word)

What materials do you need?

• Just like the driveway you will need:– Gravel (only A grade this time)– Concrete– Rebar– Wood

What to calculate?

• Volume of gravel and concrete for each.

• Area of rebar for each.

• Perimeter of each for framing wood.

Sidewalk #1(driveway to porch)

• This sidwalk curves and is approximatly ¼ of a circle.

• Imagine this was a big cylinder!

• We will need to find the volume of just the outside edge of the bottom quarter.

• To find our dimensions, we will need to find the area of the big circle and subtract the area of the small circle. Then we will divide by 4 to find ¼ of the circle.

• What material requires us to find the area?

• Rebar!

• To find the area of a circle:

• We need to find the radius of the big circle and the small circle.

• Look at the house plan!

• The radius of the small circle is the same as the width of the dining room (18’)

• The radius of the big circle is the width of the dining room plus the width of the sidewalk (4’)

• 18’+4’ = 22’

2rA

Calculate area

• Remember this is for the whole circle, we just want ¼ of it so divide by 4!

• 502.65/4 = 125.66 square feet

squarefeetA

A

A

65.502

88.101753.1520

1822 22

Put the amount in the table!

Gravel Concrete Rebar Wood

Sidewalk #1

125.66 square feet

Gravel

• To find the volume of a prism we multiply the area of the base by it’s height.

• Since we now know the area, we can multiply by the thickness of the gravel 0.5’

cubicfeetV

V

heightAbaseV

83.62

5.0*66.125

*

Add to table

Gravel Concrete Rebar Wood

Sidewalk #1

62.83 cubic feet

125.66 square feet

Concrete

• The concrete is found the same way as the gravel but with a new thickness 0.42.

cubicfeetV

V

heightAbaseV

78.52

42.0*66.125

*

Add to the table

Gravel Concrete Rebar Wood

Sidewalk #1

62.83 cubic feet

52.78 cubic feet

125.66 square feet

Calculate the wood

• Now we need to find the perimeter to find the wood.

• Remember that perimeter goes around the sidewalk.

• Since the sidewalk is 4’ wide we have two ends at 4’

• 4+4 = 8

• What about the two sides?

• The inside corner is ¼ of the circumfrence of the small circle.

• The outside corner is ¼ of the circumfrence of the big circle.

• Remember that C=2Лr

• Recall we found the radius when we found the area:– Small circle – 18– Big circle - 22

• Small Circle:C=2*3.14*18

113.04 ** don’t forget to divide by 4

113.04/4 = 28.26’

• Big Circle:C=2*3.14*22

138.16 ** don’t forget to divide by 4

138.16/4 = 34.54’

So the perimeter is 4+4+28.26+34.54 = 70.8’

Add it to the chart

Gravel Concrete Rebar Wood

Sidewalk #1

62.83 cubic feet

52.78 cubic feet

125.66 square feet

70.8’

Now try to do sidewalk #2(porch to back deck)

• Remember there are no curves for sidewalk #2

• Remember to leave space for the flower beds!

Rebar

• This sidewalk can be broken into three rectangles: Front, side, back

• Front: the width is the dining room, plus the garden plus the width of the sidewalk.

• 11+2+4 = 17 by 4

• 17*4 = 68 square feet

• Side is length of the house 55’9”

• Convert 9” to feet

• 9/12 = .75

• So the side is 55.75 * 4 = 223 square feet

• Back is the width of bedroom #2 plus the sidewalk

• 11+4 = 15

• 15 * 4 = 60 square feet

inft

x

12

9

1

Total

• Front + Side + Back• A = 68+223+60• A=351 square feet

Gravel Concrete Rebar Wood

Sidewalk #2

351 square feet

Gravel

• V=Abase*height• V=351 * 0.5• V= 175.5 cubic feet

Gravel Concrete Rebar Wood

Sidewalk #2

175.5 cubic feet

351 square feet

Concrete

• V=Abase * height• V= 351 * .42• V= 147.42 cubic feet

Gravel Concrete Rebar Wood

Sidewalk #2

175.5 cubic feet

147.42 cubic feet

351 square feet

Plywood

• Start at the front and add up all of the side lengths.

• 4 + 17+55.75+4+15+4+11+55.75+13

• Remember to include the flowerbed and the width of the sidewalk, it is helpful to look at the plan!

• =179.5’

How much plywood?

• Sidewalk #1• Remember you get 8 strips of 8’ out of one sheet

of plywood.• 70.8/8=8.85

• Sidewalk #2• 179.5/8 = 22.44 strips

• 8.85 + 22.44 = 31.29’• 31.29/8 per sheet = 3.91 or 4 sheets

Put it all on the same chart!

Gravel Concrete Rebar Wood

Sidewalk #1

62.83 cubic feet

52.78 cubic feet

125.66 square feet

70.8’

Sidewalk #2

175.5 cubic feet

147.42 cubic feet

351 square feet

179.5’

Total 238.33 cubic feet

200.2 cubic feet

476.66 square feet

4

sheets

Gravel Cost

• Remember gravel is sold by the cubic yard

• = 238.33 * 0.037 = 8.82 cubic yards

• We will need 9 cubic yards

cuyd

x

cuft 037.1

33.238

Concrete Cost

• Concrete is sold in cubic meters, convert to cubic yards first, then cubic meters.

• 200.2 * 0.037 = 7.41 cubic yards

• 7.41 * 1.82 = 13.49 cubic meters• We will need 14 cubic meters

cuyd

x

cuft 037.1

2.200

cumt

x

cuyd 82.11

41.7

Rebar Cost

• Rebar is sold 4 x 8 = 32 square feet

• We need 476.66 square feet

• 476.66/32 = 14.9 sheets

• We will order 15

Cost it outGravel Concrete Rebar Plywood

How is it sold?

Cubic Yard

Cubic meter

4x8 sheet

4x8 sheet

How much does each unit cost?

$7.00 $200 $14.45 $37.00

How many units do we need?

9 14 15 4

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

63 2800 216.75 148

Total Cost

• Grave (A-grade): $63.00

• Concrete: $2800

• Rebar: $216.75

• Wood: $148.00

• Total: $3227.75

+ tax (multiply by 1.13) = $3647.36