Calculating Roof AreaCalculating Roof Area

Rise/Run, Pythagorean Rise/Run, Pythagorean Theorem and AreaTheorem and Area

Roof Problems:Roof Problems:The Importance of DesignThe Importance of Design

Uncommon problems Uncommon problems

Trusses and RaftersTrusses and Rafters

Basic Roof StylesBasic Roof Styles

Our BuildingOur Building

The roof will have a 4/12 pitch

Roof TerminologyRoof Terminology

What are the steps to order What are the steps to order materialsmaterials

1. Determine slope1. Determine slope

2. Calculate rise of roof2. Calculate rise of roof

3. Calculate length of slope3. Calculate length of slope

4. Convert all measurements into inches (or feet)4. Convert all measurements into inches (or feet)

5. Calculate area of roof5. Calculate area of roof

6. Calculate number of square6. Calculate number of square

7. Multiply square by roofing material needs per 7. Multiply square by roofing material needs per squaresquare

8. Calculate sheathing needed8. Calculate sheathing needed

Step 1Step 1Finding the rise of the roofFinding the rise of the roof

We will have wall dimensions for the building and We will have wall dimensions for the building and the slope required.the slope required.

We will be using a 4/12 “pitch”We will be using a 4/12 “pitch”

Set up a proportionSet up a proportion

Calculate this by setting up a proportion. Calculate this by setting up a proportion. Rise over run is 4/12. Rise over run is 4/12. 10’ = 120” (10’ is ½ of the span)10’ = 120” (10’ is ½ of the span)

The rise at the ridge of the roof is 40” from The rise at the ridge of the roof is 40” from the top of the wallthe top of the wall

Finding Slope LengthFinding Slope Length

Let’s Pythagorize! (Pythagorean The.)Let’s Pythagorize! (Pythagorean The.) AA2 2 + B+ B22 = C = C22

40” leg, 120” leg40” leg, 120” leg

The slope (hypotenuse) is approximately 126-1/2”

Length of the roofLength of the roof

convert the other 20 ft. wall length convert the other 20 ft. wall length dimension into inches. dimension into inches.

20’ x 12 = 240”20’ x 12 = 240”

Finding AreaFinding Area

L x W = AL x W = A 240” x 126.5” = 30360 in240” x 126.5” = 30360 in22

Now convert to Feet: divide by 144 Now convert to Feet: divide by 144

30360” / 144 = 210 ft30360” / 144 = 210 ft22

Now we need to figure the # of “squares” Now we need to figure the # of “squares” on the roof to order shingleson the roof to order shingles

A square is 10’ x 10’ or 100 ftA square is 10’ x 10’ or 100 ft22

210 / 100 = 2.1 (number of squares)210 / 100 = 2.1 (number of squares)

We need to double that # because we We need to double that # because we have 2 sides of the roof to coverhave 2 sides of the roof to cover

Ordering shinglesOrdering shingles

We have 4.2 squareWe have 4.2 square 3 bundles of shingles cover 1 square3 bundles of shingles cover 1 square How many bundles of shingles do we How many bundles of shingles do we

need?need?

4.2 x 3 = 12.6 4.2 x 3 = 12.6

Round up to Round up to AT LEASTAT LEAST 13 13

Estimating Roof SheathingEstimating Roof SheathingOSB or PlywoodOSB or Plywood

420 sq. ft.420 sq. ft. Each sheet of OSB is 4’ x 8’Each sheet of OSB is 4’ x 8’ What is the area of a sheet of OSB?What is the area of a sheet of OSB? 32 ft32 ft22

Calculating amount by Calculating amount by

420 / 32 = 13.125420 / 32 = 13.125

We need at least 14 sheets of OSBWe need at least 14 sheets of OSB

Math Practice QuestionsMath Practice Questions

Find the pitch for the following roofs:Find the pitch for the following roofs:

Total RiseTotal Rise SpanSpan PitchPitch 8’8’ 24’ 24’ 8/24 =1/38/24 =1/3 6’6’ 36’ 36’ 9’ 9’ 24’ 24’ 12’ 36’12’ 36’ 8’ 32’8’ 32’

Total RiseTotal Rise SpanSpan PitchPitch

8’8’ 24’24’ 8/24 =1/3 8/24 =1/3

6’6’ 36’36’ 6/36 =1/6 6/36 =1/6

9’ 9’ 24’24’ 9/24 =3/8 9/24 =3/8

12’ 36’12’ 36’ 12/36 = 1/3 12/36 = 1/3

8’ 32’8’ 32’ 8/32 =1/48/32 =1/4

Word problemsWord problems

2.2. Ima Genius is trying to convince her dad to buy new Ima Genius is trying to convince her dad to buy new carpet for her bedroom. The dimensions of her room are carpet for her bedroom. The dimensions of her room are 10’ by 12’. How many square feet of carpet would her 10’ by 12’. How many square feet of carpet would her dad need to buy? Draw and label a diagram and solve dad need to buy? Draw and label a diagram and solve showing your work.showing your work.

3. Heeszo Smart (Ima’s cousin) decided to carpet his 3. Heeszo Smart (Ima’s cousin) decided to carpet his bedroom also. He found 3 dozen carpet samples at a bedroom also. He found 3 dozen carpet samples at a garage sale. Each one measures 2’ by 2’. His room is 10’ garage sale. Each one measures 2’ by 2’. His room is 10’ by 14’. Does he have enough carpet samples? Explain.by 14’. Does he have enough carpet samples? Explain.

4. Ima’s dad finds bundles of floor tiles at a yard sale. He 4. Ima’s dad finds bundles of floor tiles at a yard sale. He bought 6 bundles of 10 tiles. Each tile is 16” by 16”. How bought 6 bundles of 10 tiles. Each tile is 16” by 16”. How many tiles will be needed to cover the floor of her room? many tiles will be needed to cover the floor of her room? Does he have enough tiles?Does he have enough tiles?