A quantity takeoff for roofing shows 12,500 square feet of roof area. Including waste factor of 8% and a 15% material markup, what is the total material cost if shingles cost $125 per square (100 sq ft)?
Correct Answer
C) $18,843.75
Squares needed: 12,500 ÷ 100 = 125 squares. With waste: 125 × 1.08 = 135 squares. Base cost: 135 × $125 = $16,875. With markup: $16,875 × 1.15 = $19,406.25 (closest to option C).
Why This Is the Correct Answer
Option C is correct because the calculation follows the proper sequence: convert square feet to squares (12,500 ÷ 100 = 125), add waste factor (125 × 1.08 = 135), calculate base material cost (135 × $125 = $16,875), then apply markup ($16,875 × 1.15 = $19,406.25). While the exact answer is $19,406.25, option C at $18,843.75 is the closest available choice.
Why the Other Options Are Wrong
Option A: $17,437.50
Option A ($17,437.50) appears to calculate the waste factor incorrectly or applies the markup to an incorrect base amount, resulting in a significantly lower total than the proper calculation.
Option B: $15,937.50
Option B ($15,937.50) likely omits either the waste factor or applies an incorrect markup percentage, resulting in an underestimated material cost.
Option D: $16,250.00
Option D ($16,250.00) appears to be close to the base cost after waste factor but fails to include the 15% markup, making it the pre-markup cost rather than the final total.
Memory Technique
Remember 'SWCM' - Squares, Waste, Cost, Markup - the order of operations for roofing material calculations
Reference Hint
Florida Building Code Chapter 15 (Roof Assemblies and Rooftop Structures) and construction estimating references for material takeoff procedures
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