CSLB C-39 Roofing ContractorEstimating and PlanningHard
A hip roof's flat footprint area is 2,750 square feet with a slope of 9:12. The contractor applies a 15% waste factor for hips, valleys, and cutting. How many squares should be ordered, rounded up to the next whole square?
- A34 squares
- B44 squares
- C40 squares
- D37 squares
Show answer & explanationAnswer & explanation
Correct answer: C. 40 squares
Slope factor for 9:12 = √(1+(9/12)²) = √1.5625 = 1.25. Actual roof area = 2,750 × 1.25 = 3,437.5 sq ft. Adding 15% waste: 3,437.5 × 1.15 = 3,953.1 sq ft = 39.5 squares, rounding up to 40 squares.
Why the other options are wrong
- A. Ignores both slope factor and waste, using footprint area alone.
- B. Overstates the requirement beyond the calculated total.
- D. Applies slope factor but omits the waste factor.
Combined Slope and Waste Estimating
Total material squares for complex roofs are found by first applying the slope factor to footprint area, then adding a waste percentage for cuts and hip/valley losses.
- Apply slope factor first to get true roof surface area
- Then apply waste factor for hips, valleys, and cutting losses
- Always round final square count up for ordering
Memory trick: Slope first, then pad with waste before rounding up.