Roofing
Roofing Square
A unit of roofing measurement equal to 100 square feet of roof surface area, used to quantify materials like shingles, underlayment, and decking.
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In the Field
To get actual roof area, multiply the plan (footprint) area by a slope factor. A 4:12 pitch has a slope factor of 1.054; a 6:12 is 1.118; a 12:12 is 1.414. Add 10–15% for waste, hips, and valleys.
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Rule of Thumb
One square of 3-tab or architectural shingles covers 100 sq ft. Add 10% waste on simple gable roofs, 15–20% on complex roofs with multiple hips, valleys, and dormers.