CSLB C-39 Roofing ContractorEstimating and PlanningHard
A chimney measures 48 inches wide, measured perpendicular to the roof slope, and sits on a roof with a 6:12 slope. A cricket (saddle) must be built behind the chimney to divert water, with its peak height calculated as half the chimney width multiplied by the roof's rise-to-run ratio. What height should the cricket peak be built to?
- A9 inches
- B6 inches
- C16 inches
- D12 inches
Show answer & explanationAnswer & explanation
Correct answer: D. 12 inches
Half the chimney width is 48 ÷ 2 = 24 inches. The 6:12 slope equals a rise-to-run ratio of 0.5. Multiply: 24 × 0.5 = 12 inches, which is the required cricket peak height.
Why the other options are wrong
- A. Results from using an incorrect ratio less than 0.5.
- B. Too shallow; does not use the full half-width calculation.
- C. Overestimates by applying more than the 6:12 ratio.
Cricket Height Calculation
A chimney cricket's peak height is found by multiplying half the chimney's perpendicular width by the roof's rise-to-run ratio.
- Half-width × slope ratio = cricket peak height.
- 6:12 slope equals a 0.5 ratio.
- Crickets divert water around wide chimneys and prevent ponding.
Memory trick: Half the width, times the slope, equals the peak.