CSLB C-39 Roofing ContractorLow-Slope RoofingHard
A mechanically attached TPO membrane is installed using 10-foot-wide sheets. Manufacturer specifications require fasteners spaced 12 inches on center along each seam only, with no additional fasteners in the field of the sheet. How many fasteners are required per 10 ft × 10 ft square in the field zone?
- A10 fasteners
- B5 fasteners
- C12 fasteners
- D8 fasteners
Show answer & explanationAnswer & explanation
Correct answer: A. 10 fasteners
Each 10-ft-wide sheet produces one seam per 10-ft width. Along that 10-foot seam, fasteners spaced at 12 inches (1 ft) on center yield 10 fasteners per square (10 ft ÷ 1 ft = 10).
Why the other options are wrong
- B. This undercounts the fasteners along the full 10-ft seam length.
- C. This overcounts fasteners beyond the specified 12-inch spacing.
- D. This does not match the correct spacing calculation.
Mechanically Attached Membrane Fastener Calculation
A method for determining fastener quantity along membrane seams by dividing the seam length by the specified on-center fastener spacing.
- Fasteners are typically placed along seams, not in the sheet field
- Spacing is given in inches or feet on-center
- Wind uplift zones (corner/perimeter/field) require different fastener densities
Memory trick: Ten feet of seam, one foot apart, gives ten fasteners from the start.