NASCLA Accredited Commercial General ContractorThermal and Moisture ProtectionMedium
A commercial roofing project involves the installation of a new TPO membrane. The specifications call for a fully adhered system. To ensure proper adhesion, the substrate must be clean, dry, and primed. The contractor needs to calculate the coverage rate for the primer. If a 5-gallon bucket of primer covers approximately 1,500 square feet, and the roof area is 12,000 square feet, how many 5-gallon buckets of primer are needed?
- A6 buckets
- B4 buckets
- C8 buckets
- D10 buckets
Show answer & explanationAnswer & explanation
Correct answer: C. 8 buckets
To find the number of buckets needed, divide the total roof area by the coverage rate per bucket: 12,000 sq ft / 1,500 sq ft/bucket = 8 buckets.
Why the other options are wrong
- A. Incorrect calculation: 12,000 / 2,000 = 6, which is a common miscalculation.
- B. Incorrect calculation: 12,000 / 3,000 = 4, which assumes double the coverage.
- D. Incorrect calculation: 12,000 / 1,200 = 10, which assumes a lower coverage rate.
Primer Coverage Rate
Primer coverage rate refers to the area (typically in square feet) that a specific volume of primer (e.g., a gallon or bucket) can effectively cover on a given substrate.
- Coverage varies by primer type, substrate porosity, and application method.
- Essential for accurate material ordering and project budgeting.
- Always refer to manufacturer's specifications for precise rates.
Memory trick: Quantity: Total Area Divided by Rate, Always Estimate Up.