TPO Over an Existing Roof: When It Works — Inspection Notes
What a real inspection covers on a TPO roof in the Lankershim corridor, and what usually gets skipped.
A roof inspection is only as good as what gets looked at, and a lot of what gets called an inspection is a walk round the garden with a phone camera. This is what a real one covers on a TPO roof in the Lankershim corridor.
What actually matters
TPO is a single-ply membrane that is heat-welded rather than glued, which means the roof is only as good as its seams. A properly welded seam is stronger than the sheet either side of it; a cold weld looks identical and is not a seam at all. An inspection that does not account for that is looking at the wrong layer.
The detail that is usually left out
An inspection is only as good as what gets looked at, and photographs of specific defects are what let you get a second opinion without a second visit. Weld testing is the item to insist on. A probe run along every seam while the crew is still on site costs nothing and finds the cold welds that would otherwise be discovered by a tenant in December. Anything under half an hour on an average house has skipped something.
What is specific to the Lankershim corridor
Along the Foothill corridor the buildings are largely commercial: big low-slope areas carrying rooftop plant, walked on regularly by trades who are not thinking about the membrane. Dust off the slopes settles on the surface and washes into the drainage with every storm. Older commercial stock with large low-slope areas, parapets, and equipment that needs servicing.
The full inspection list
- Seam integrity, probed along the full length rather than spot-checked
- Punctures and abrasion, especially on traffic routes to rooftop plant
- Membrane shrinkage and any resulting tension at the perimeter
- Flashing and termination bar at every wall, curb and upstand
- Drain sumps and clamping rings, checked and clear
- Fastener plates showing through the membrane surface
- Weathering and chalking of the surface, particularly on exposed elevations
Common questions
How long should an inspection take?
Long enough to get on the roof and into the attic. Anything under half an hour on an average house has skipped something.
Should I expect photographs?
Yes, and of the specific defects rather than general views. Photographs are what let you get a second opinion without a second visit.
The honest summary
TPO is a good system installed properly and an expensive mistake installed quickly. Seams and punctures decide its life, so protect the surface and test the welds. In the Lankershim corridor the thing to watch is membrane condition around the rooftop plant, parapet terminations, and every drain and scupper on the roof.
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