CSLB C-39 Roofing ContractorEstimating and PlanningHard
A roof's flat footprint area is 3,000 square feet, and the roof's slope factor yields a calculated roof surface area of 3,600 square feet (36 squares). Due to numerous hips, valleys, and dormers requiring extensive cutting, the contractor applies an additional 18% waste factor on top of the slope-adjusted area. How many squares should be ordered, rounded up to the nearest whole square?
- A42 squares
- B43 squares
- C40 squares
- D41 squares
Show answer & explanationAnswer & explanation
Correct answer: B. 43 squares
Applying the 18% waste factor to the slope-adjusted area: 3,600 sq ft × 1.18 = 4,248 sq ft = 42.48 squares, which must be rounded up to 43 whole squares to ensure sufficient material.
Why the other options are wrong
- A. This is close but rounds down instead of up from 42.48.
- C. This undercounts by omitting a substantial portion of the waste factor.
- D. This still falls short of the full waste-adjusted requirement.
Complex Roof Waste Factor
Highly cut-up roofs with numerous hips, valleys, and dormers require an additional waste percentage beyond the basic slope-adjusted area to account for material lost in cutting and fitting irregular sections.
- Waste factors for complex roofs often range from 15-20%
- Applied after the slope factor has already been calculated
- Always round the final square count up, never down
Memory trick: More cuts and corners mean more waste to order.