CSLB C-39 Roofing ContractorLow-Slope RoofingMedium
A general contractor is selecting a mechanically attached TPO membrane for a warehouse roof with anticipated heavy rooftop foot traffic and equipment servicing. Which membrane thickness would provide the best long-term puncture and wear resistance compared to a thinner alternative?
- A45-mil TPO
- B50-mil TPO
- CThickness does not affect puncture resistance in single-ply membranes
- D60-mil TPO
Show answer & explanationAnswer & explanation
Correct answer: D. 60-mil TPO
Among common TPO thicknesses (45, 50, 60 mil), the thickest membrane (60 mil) provides the greatest reserve material over the reinforcing scrim, giving the best resistance to punctures and abrasion from foot traffic and equipment.
Why the other options are wrong
- A. 45-mil is the thinnest common option and offers the least puncture resistance.
- B. 50-mil is an improvement but still thinner than the best option offered.
- C. Thickness directly affects puncture and wear resistance in single-ply membranes.
TPO Membrane Thickness
TPO single-ply membranes are commonly manufactured in 45, 50, and 60-mil thicknesses, with thicker membranes providing greater puncture and wear resistance.
- Thickness measured over the reinforcing scrim
- Thicker membranes cost more but last longer under traffic
- High-traffic or ballasted areas often specify 60-mil or greater
Memory trick: Thicker skin, tougher against the world's kicks.