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Roofing Expert

A Step-by-Step Guide to Accurately Calculating Your Roof Area

If you're planning to replace your roof, understanding its area is essential to estimate the total cost, including the price of shingles per square foot. Our roofing experts at DMV Roofers have outlined two effective ways to calculate your roof area: using the roof pitch for estimates and taking precise measurements for accuracy.


Method 1: Estimating Roof Area with Pitch Calculation

1. Measuring the Pitch

   - Measure out 12 inches on your large level and mark the spot.     - Position a ladder securely at the gable end of your house and climb up.     - Place the level flat against the side of the house, aligning it with the gable trim.     - Measure vertically from the 12-inch mark on the level to the base of the gable trim—this is the "rise" of your roof.     - Record the rise measurement as your roof’s pitch in “# in 12” format. (e.g., a rise of 4 inches would be 4 in 12.)

2. Calculating Estimated Roof Area   - Divide your roof pitch by 12. For example, a pitch of 4 in 12 becomes 4 ÷ 12 = 1/3.     - Square the result: (1/3)² = 1/9.     - Add 1 to this squared number: 1/9 + 1 = 10/9.     - Calculate the square root of this sum: √(10/9) = 1.05.     - Determine your home’s square footage for one floor. For instance, if your two-story home is 2,600 sq. ft., one floor equals 1,300 sq. ft.     - Multiply your floor area by the calculated pitch factor: 1,300 sq. ft. × 1.05 = 1,365 sq. ft. of estimated roof area.


Method 2: Accurate Roof Area Calculation

1. Revisiting Pitch Calculation     - Divide the roof pitch by 12 (e.g., 4 in 12 = 1/3).     - Square this quotient (1/3)² = 1/9.     - Add 1: 1/9 + 1 = 10/9.     - Find the square root of the sum: √(10/9) = 1.05.

2. Measuring House Dimensions   - Measure the length of your house, including any overhangs.     - Measure the width of your house, also including overhangs.     - Multiply these dimensions to find the area. For example, a length of 40 ft × a width of 30 ft = 1,200 sq. ft.

3. Final Roof Area Calculation

  • Multiply the house area by the pitch factor: 1,200 sq. ft. × 1.05 = 1,260 sq. ft.

  • For a gable roof, add 10% to account for hips, ridges, and waste: 1,260 sq. ft. × 1.10 = 1,386 sq. ft.

  • For a cottage-style roof, add 17% instead: 1,260 sq. ft. × 1.17 = 1,474 sq. ft.

By following these methods, you can accurately estimate your roof area and costs. For expert advice or assistance, reach out to the DMV Roofers team!




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