- 1
roof pitch
Fisrt, calculate the pitch of your roof. Pitch is a measure of how much the roof rises vertically for every horizontal foot.
On the gable side, measure 1 foot horizontally from the base of the roof and mark that spot with a pencil. Now, measure vertically from that spot to the underside of the roof. Let's say you get 7.5 inches. Then the pitch of your roof is 7.5/12. If you convert this to a decimal (by dividing 7.5 by 12), you get 0.625. - 2). Next, take the decimal you obtained in step one, and square it: (0.625)(0.625) = 0.390625. Now, add 1 to that number: 1 + 0.390625 = 1.390626. Last, use your calculator to find the square root of that number: sqrt(1.390625) = 1.1792.
Since most homes have some roof overhang all around the sides of the house, round this number up to the nearest hundreds place, so you get 1.18. - 3). Take the last number from step 3, and multiply by your home's total square footage. For example, if your house is 1500 square feet, then you get (1500)(1.18) = 1770. And now, multiply that number by the cost per square foot of roofing material. For example, if the cost is $1.25 per square foot, then your total roofing estimate is (1770)(1.25) = $2212.50
- 4
roof angle cosine
Sometimes the slope of a roof is measured as an angle. If you know the pitch angle, you can make an accurate roofing estimate. First, use the chart to find the cosine of the angle. For example, if your roof is pitched at an angle of 35 degrees, then cos(35) = .819 from the chart. - 5). Next, divide the square footage of your home by the number you got in the step above. For example, if your home has is 1150 sq feet, then 1150/.819 = 1404. Now, multiply this number by the cost per square foot of roofing material. So if the roofing costs $.95 per square foot, then the total cost is (1404)(.95) = $1333.80
SHARE
