How to Measure a Roof to Determine How Many Shingles Are Needed
When you install new shingles on a roof, each shingle must overlap the one below it. This is necessary to ensure water runs off and doesn't seep between the shingles. However, it does complicate the task of measuring a roof for shingles needed. Fortunately, vendors take care of this by packaging shingles in squares. One square, usually composed of three bundles of shingles, contains enough material to cover 100 square feet of roof, including an adequate allowance for overlapping. Does this Spark an idea?
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Instructions
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1
Draw an outline of the roof, marking in each section. Almost all roofs are a collection of rectangles and triangles. If you have sections that are combinations of the two, divide them up into triangles and rectangles on your drawing.
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2
Be mindful of safety. A fall from a roof can result in a major injury. You can rent or buy a "fall-arrest" system at your building supply store. Even with this security, do not work in rainy or windy weather and stop when it starts getting dark. Finally, take stock of your own experience and ability. Some roofs are extremely steep and you may need to leave them to professionals.
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3
Determine the length and width of each rectangle using a tape measure. Multiply the length by the width of each to find the square footage of each section.
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4
Measure the base side of each triangle. The base is the side opposite the largest angle. Next, use the tape measure and a carpenter's square to find and measure the perpendicular line from the base to the apex of the largest angle, which is called the height of the triangle. Multiply the base by the height and divide by two to calculate the square footage of triangular sections.
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5
Add up the square footage of each section (from sections 3 and 4) to find the total area of the roof. Add in 5 percent as a reserve for waste and shingles that must be trimmed to fit. You'll need to buy enough shingles to cover this much roof area.
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6
Find the number of squares in the roof area. Round up the number of square feet to the next greater hundred and divide by 100. For example, if you measured 3,080 square feet (from Step 5) round up to 3,100 and divide by 100 for a total of 31 squares. This is the amount of shingles you'll need to cover the roof.
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