CSLB C-39 Roofing ContractorEstimating and PlanningMedium
A low-slope built-up roof deck measures 3,200 square feet. Modified bitumen cap sheet rolls provide 100 square feet of net coverage per roll after side and end laps are accounted for. How many rolls are required if no additional waste is added?
- A30 rolls
- B34 rolls
- C28 rolls
- D32 rolls
Show answer & explanationAnswer & explanation
Correct answer: D. 32 rolls
Total roof area ÷ net coverage per roll = 3,200 ÷ 100 = 32 rolls exactly, with no waste factor needed since laps are already excluded from the net coverage figure.
Why the other options are wrong
- A. This also falls short of covering the full 3,200 sq ft deck.
- B. This overstates the requirement beyond the calculated need.
- C. This underestimates the rolls needed for full coverage.
Cap Sheet Net Coverage
Built-up and modified bitumen roofing rolls are rated by net (effective) coverage after side and end laps, so total roll count equals total area divided by net coverage per roll.
- Net coverage already accounts for overlaps
- Divide total roof area by net coverage per roll
- Low-slope roofs often use cap sheets rated in net square footage
Memory trick: Net coverage means no extra math for laps.