Things You'll Need:
- Helper Ladder Tape measure Calculator Pencil and paper
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Step 1
With a helper, climb onto your roof and measure the surface area. Starting on one full side of the roof, stretch the tape measure for the width, from one side edge to the other, and round the number up to the nearest foot. Measure the length, from the peak down to the end of the overhang, in the same fashion.
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Step 2
Multiply the two numbers to get the square footage of that section of the roof. For example, a roof that is 20 feet tall from the peak to the end of the overhang, and 50 feet across from side to side, is 1,000 square feet.
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Step 3
Repeat the process for each full section of the roof, including dormers. For areas that are triangular rather than square, measure the full length from peak to overhang, and multiply it by the widest part of the width.
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Step 4
Once you have your total combined square footage calculated for the whole roof, add 10 percent to it. For example, if it's a 5,000 square foot roof, make your final working number 5,500.
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Step 5
Divide your working number by 100 to get the number of roofing "squares" you need (55 squares, in this case). That's the number you should tell your home improvement store when you price the roofing shingles and order them for delivery to the job site. Prices for roofing shingles vary widely, depending on style and quality, from less than $50 per square to more than $100.
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Step 6
Felt roofing underlayment is purchased in rolls and measured in squares, the same measurement used to buy the shingles, so price for 55 squares of roofing felt. (Prices for felt paper are around $5 per square). In addition, you will need around 350 roofing nails per square, or about 19,000 nails total in this example (55 squares times 350 roofing nails). It sounds like a massive amount, but one 50-pound box of nails (generally between $50 to $100) will more than cover it.
