Behind the bay windows and cornices, most San Francisco Victorians, Edwardians and Sunset row houses have a flat or low-slope roof. Those roofs need a sealed membrane, not shingles. On a low pitch, water moves too slowly to shed off overlapping shingles, works under the laps and leaks. Anything under roughly a 2:12 slope needs a membrane.
TPO or EPDM?
| TPO | EPDM | |
|---|---|---|
| What it is | Reflective single-ply membrane, usually white | Black synthetic rubber membrane |
| Strengths | Reflects heat; the simplest path where a cool roof is required | Long, proven track record; a good fit for shaded roofs and some commercial uses |
| Typical life when installed well | 20–30 years | 20–30 years |
Either is a sound choice on a San Francisco house. What decides the result is drainage and the quality of the seams and flashing, not the brand of membrane. See the flat and low-slope roofing guide for more.
Does Title 24 force me to use a white roof?
Not on a house in San Francisco. Every SF ZIP code is in building climate zone 3 on the California Energy Commission’s ZIP list, and the 2025 Energy Code’s cool-roof rules for low-slope single-family reroofs apply only in zones 4 and 6–15. Commercial and mixed-use buildings are different: a low-slope reroof covering more than half the roof or 2,000 sq ft needs a cool roof in every zone. Details: does a San Francisco reroof need a cool roof.
Where do San Francisco flat roofs fail?
- Parapets. Cracked parapet caps and tired base flashing let water into the wall.
- Shared walls. The joint with the neighboring building on attached homes.
- Lightwells and skylights. Curbs and flashing that were never rebuilt properly. See replacing skylights during a reroof.
- Scuppers and drains. Leaves and debris cause ponding, and ponding finds every weak seam during a winter storm.
Can a new membrane go over the old one?
Only in limited cases. California’s reroofing code does not allow a recover over a roof that already has two or more layers or is water-soaked or deteriorated. See roofing over an old roof.
What does it cost?
Our San Francisco cost table puts a flat TPO roof at about $10,000–$22,000 for roughly 2,000 sq ft of roof, including tear-off and basic permit fees. Parapets, access, the number of old layers and deck repair move the number. Your actual price comes from an on-site inspection.
Request a free inspection and written estimate or call (415) 410-7917. Related: flat roof leak repair, roofing in San Francisco.
Sources: CEC building climate zones by ZIP code; CRRC chart of 2025 California Energy Code cool roof requirements.
Related services and local pages
- Roof Repair & Leak Detection
- Roof Replacement
- Commercial & Residential Roofing
- San Francisco roofing contractor
- Roofing materials guide
Sources
- California Energy Commission: building climate zones by ZIP code
- Cool Roof Rating Council: 2025 California Energy Code cool roof requirements (chart)
- 2025 California Residential Code R908, reroofing (code text on GoCodebook)
Rules and maps change; confirm requirements for your address with your city or county building department.
Have a follow-up question for your specific roof?
Free, no-obligation on-site inspection. Honest written report — yours to keep whether you hire us or not.