CSLB General Building (B)Planning and EstimatingMedium
A contractor is planning to pour a concrete driveway that is 60 feet long, 10 feet wide, and 4 inches thick. If concrete is ordered in full cubic yard increments, how many cubic yards of concrete should be ordered to account for standard waste?
- A6 cubic yards
- B8 cubic yards
- C10 cubic yards
- D12 cubic yards
Show answer & explanationAnswer & explanation
Correct answer: B. 8 cubic yards
First, calculate the volume in cubic feet (60 ft * 10 ft * 0.333 ft = 199.8 cubic feet). Convert to cubic yards by dividing by 27 (199.8 / 27 = 7.4 cubic yards). With a standard 10% waste factor, this becomes 7.4 * 1.10 = 8.14 cubic yards. Since concrete is ordered in full cubic yard increments, 8 cubic yards is the closest full yard without going under the required amount, considering the waste factor.
Why the other options are wrong
- A. Incorrect; this does not account for the correct volume or waste factor.
- C. Incorrect; this overestimates the required concrete significantly.
- D. Incorrect; this significantly overestimates the required concrete.
Concrete Volume & Waste
Estimating concrete volume involves calculating cubic feet, converting to cubic yards, and adding a waste factor (typically 5-10%) before rounding up to the nearest full yard for ordering.
- 1 cubic yard = 27 cubic feet
- Common waste factor: 5-10%
- Always round up to the nearest full cubic yard for ordering
Memory trick: Calculate, Convert, Cushion, Confirm!