CSLB C-39 Roofing ContractorEstimating and PlanningHard
A roofer installs asphalt shingles using 4 nails per shingle, with 80 shingles per square. The roofing nails used run approximately 320 nails per pound, and nails are sold only in 50-pound boxes. For a 24-square roof, how many boxes of nails must be ordered?
- A3 boxes
- B2 boxes
- C4 boxes
- D1 box
Show answer & explanationAnswer & explanation
Correct answer: D. 1 box
Nails per square: 4 nails × 80 shingles = 320 nails per square, which equals exactly 1 pound per square at 320 nails/lb. For 24 squares, total weight is 24 pounds. Since 24 pounds is less than one 50-pound box, only 1 box is needed.
Why the other options are wrong
- A. Far exceeds the actual 24-pound requirement.
- B. Overestimates; 24 pounds does not require a second box.
- C. Grossly overestimates the nail weight needed.
Fastener Weight Takeoff
Nail quantities can be converted to weight using nails-per-pound ratings, then compared against box sizes to determine how many boxes to order.
- Nails per square = nails per shingle × shingles per square.
- Divide total nails by nails-per-pound to get weight needed.
- Round up box purchases since partial boxes aren't sold.
Memory trick: Nails per shingle times shingles per square, then convert to pounds.