CSLB C-39 Roofing ContractorEstimating and PlanningMedium
A contractor estimates a roofing job requires 22 squares of shingles priced at $145 per square, and adds a 10% material waste allowance to the order. What is the total material cost?
- A$3,630
- B$3,190
- C$3,509
- D$3,335
Show answer & explanationAnswer & explanation
Correct answer: C. $3,509
With a 10% waste allowance, order quantity = 22 × 1.10 = 24.2 squares. Total cost = 24.2 × $145 = $3,509.
Why the other options are wrong
- A. This overstates the waste-adjusted total cost.
- B. This is the cost without any waste allowance applied.
- D. This undercounts the waste-adjusted square total.
Waste-Adjusted Material Cost
Total material cost is found by first adding the waste percentage to the calculated squares, then multiplying the adjusted quantity by the price per square.
- Waste allowance is added before pricing, not after
- Order quantity = base squares × (1 + waste %)
- Common waste allowances range from 10-15% for standard roofs
Memory trick: Pad the squares first, then price the pile.