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Roofing Research

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Calculating the quantity of materials needed for a roofing job can be complicated, especially if the roof is complex. It can also be dangerous; some roofs are so complex that the only way to get an accurate estimate is to climb onto the roof and measure each plane separately. In addition to determining the quantity of shingles, you must also determine how much underlayment, drip edge, flashing and other products will be required. For all of these reasons, it is best to have a professional roofing contractor determine the materials needed for the job. However, if you are just trying to get a rough estimate, the following information may help.

Definition of Terms
Before continuing, it might be helpful to define certain terms used.

• A square …show more content…

It is always expressed with the vertical rise first. To illustrate, if a roof rises 14 inches for every 12 inches of horizontal length, the pitch would be expressed as 14/12.
• The ridge is the horizontal area where the tops of two roof planes meet.
• The hips are the sloping vertical areas where two roof planes meet.
• Valleys are the channels where two roof planes meet.

Estimating Roof Area Using Pitch and Square Footage
If you are mathematically inclined or have a good calculator, you can estimate the roof area if you know the pitch of your roof and the square footage of your home. To illustrate, if your pitch is 4/12 and your two-story home has 1,400 square feet on each floor, these are the calculations.

• Divide the pitch. For a 4/12 pitch, the answer is 1/3.
• Square the above answer, which in this example would yield 1/9.
• Add 1, expressed as a fraction. That is, you would add 9/9 + 1/9 for a total of 10/9.
• Take the square root of 10/9, which is approximately 1.054.
• Multiply 1.054 by 1,400, the square footage of the home used in this example. You should get …show more content…

You will need at least 14.756 squares of roofing. However, you should add about 10 percent for starter strips, valleys, waste and hip and ridge.

Estimating Materials Based on Actual Measurements
Measuring each roof plane requires you to actually go onto your roof. If your roof has a number of planes and numerous hips, ridges and valleys, this is the most accurate way to calculate the materials needed. Take a metal tape measure and a pen and paper. Measure each plane's length and width. Record your measurements. Once you are safely on the ground, use your measurements to determine the square footage.

• For rectangular areas, multiply the length by the width. For example, if a plane measures 30 feet by 100 feet, this would be 3,000 square

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