CSLB C-39 Roofing ContractorLow-Slope RoofingMedium
A crew is installing a gravel-surfaced BUR system on a 3,000 sq ft roof section. The flood coat of asphalt is applied at 60 lb per square, and gravel is embedded at a rate of 400 lb per square. How many total pounds of gravel are required for the section?
- A4,000 lb
- B1,200 lb
- C18,000 lb
- D12,000 lb
Show answer & explanationAnswer & explanation
Correct answer: D. 12,000 lb
3,000 sq ft ÷ 100 = 30 squares. Gravel rate is 400 lb/square, so 30 squares × 400 lb = 12,000 lb of gravel required.
Why the other options are wrong
- A. This mistakenly uses the flood coat asphalt calculation logic instead of gravel.
- B. This figure would only cover 3 squares, far too low.
- C. This overstates the requirement by using an incorrect multiplier.
BUR Gravel Embedment Rate
The standard application rate of ballast gravel embedded into the hot asphalt flood coat of a built-up roof, typically 400 lb per square, to protect the membrane from UV and weathering.
- 1 square = 100 sq ft
- Standard gravel rate: ~400 lb/square
- Flood coat asphalt rate: ~60 lb/square
Memory trick: Squares times four-hundred gives your gravel grand.