Two systems dominate flat-roof bids in Los Angeles, and they solve the same problem with opposite philosophies. TPO, at $13–$19.50 per square foot, is a single engineered membrane with heat-welded seams and a reflective white face. Torch down, at $10–$15 per square foot, is layered polymer-asphalt fused by flame into a thick, tough mat. Neither is simply better; each is better at different things, so the fastest route to a decision is matching the roof’s job to the system’s strengths.
The scorecard
| Factor | TPO | Torch down |
|---|---|---|
| Installed cost | $13–$19.50 /sq ft | $10–$15 /sq ft |
| Heat reflection | Excellent, white surface | Fair, granule surface |
| Cool-roof code | Complies as-is | Needs reflective cap or coating |
| Foot traffic / decks | Punctures possible | Built for it |
| Seam integrity | Welded, monolithic | Torched laps, very good |
| Future repairs | Needs a membrane roofer | Any competent crew |
| Install risk | Weld skill dependent | Open flame on the building |
Pick by scenario
Bedrooms or living space directly below the roof. TPO. The reflectivity difference is not subtle in August, and it satisfies the cool-roof rules described in our compliance guide without extra products.
The roof doubles as a deck, or crews service equipment up there. Torch down. Its mass forgives traffic that stresses a membrane, and scars patch invisibly.
Budget decides. Torch down opens lower, and on a garage, rental, or workshop where energy performance is nobody’s priority, the savings are clean.
You plan to own the home for decades. Slight edge to TPO for its monolithic seams, provided, and this is the entire caveat, the installer is a true membrane specialist. A mediocre TPO weld fails sooner than a mediocre torch lap.
The building or jurisdiction frowns on open flame. TPO by default, though cold-applied modified bitumen exists as a middle path.
What to demand from either bid
Flat-roof quality is workmanship-shaped, so make bids prove it: membrane thickness or ply count in writing, named details for parapets and drains, ponding-water correction included rather than ignored, and recent local references on the same system. The deeper single-system write-ups are here: TPO explained and torch down explained, with whole-project totals in the flat roof cost guide.
Figures on this page are informational estimates based on regional pricing data and automated roof measurements. They are not quotes or bids. Actual pricing requires an on-site inspection by a licensed contractor.