This article describes the basic math to calculate roof materials. When you calculate a roof to figure out how much roofing material to order the. If you have ever asked yourself "how many squares is my roof?" this article will help you find the answer. This article teaches you the math formula to figure out how much roofing and underlayment you need to order. A little math is needed to calculate the area when it has a slope to it like most residential roofs do.
Roofing is talked about using the term "square", as in "This roof is 16 squares". A "square" refers to 100 square feet of roof or a 10 foot by 10 foot area. So a roof that has 1600 square feet of area has 16 squares. Remember that unless the roof is flat, the square footage of the building is different than the square footage of the roof. This is because of the pitch of the roof and the overhangs.
Determine the squre footage of the house foot print by measuring the length and width of the house including the overhangs. For example, if you have a simple 30 foot by 40 foot home you add the overhangs to those dimensions. If the overhangs are 1'-6" then you have 3' extra each dimension. 33' x 43' = 1419 sf. flat.
The roof pitch is the amount of slope. The slope is described by stating the "rise" in inches (how far up it goes) over the "run" in inches (how far horizontal it goes).The pitch is the part of the calculating roof problem that makes it a little tricky but keep reading the answers are here.
For this example we will use a 6 in 12 pitch. For every 6 inches the roof goes up to the peak it goes 12 inches horizontally. 6/12
6x6=36 (square of the rise)
12x12=144 (square of the run)
36 + 144 = 180
The square root of 180 is 13.417
13.417 / 12 = 1.118
Our area from step 1 was 1419 sf of flat roof so:
1.118 x 1419 = 1586 square feet
1586 / 100 = 15.86. Round this number up and thats your answer, 16 squares!
Add 10% to this number for waste and it is 17 1/2 squares.
There you have it, the simple formula to calculate roof materials. Now is the fun part, ordering it and installing it. See our articles on how to install different types of roofing.