CSLB C-39 Roofing ContractorLow-Slope RoofingMedium
After hot-air welding TPO membrane seams, a quality control technician wants to verify the seam is fully fused. Which field test is the standard method for checking seam integrity?
- AProbing the seam edge with a blunt tool to check for separation
- BVisual inspection from a distance without touching the seam
- CMeasuring seam width with a tape measure only
- DWater flood test of the entire roof
Show answer & explanationAnswer & explanation
Correct answer: A. Probing the seam edge with a blunt tool to check for separation
The standard quality control method for heat-welded thermoplastic seams is a probe test, in which a rounded, dull tool is run along the seam edge to detect any lack of fusion or voids; a properly welded seam will not separate under this probing.
Why the other options are wrong
- B. Visual-only inspection cannot detect subsurface fusion defects.
- C. Seam width alone does not confirm fusion quality.
- D. Flood testing checks for leaks after full installation, not seam fusion quality specifically.
Seam Probe Test
A field quality control method using a dull probe tool to check for full fusion along heat-welded thermoplastic membrane seams.
- Performed after seams cool
- Detects voids or cold welds
- Standard for TPO and PVC seam QC
Memory trick: Probe the seam, don't just dream it's sealed.