Roofing in San Francisco: what actually matters here
San Francisco is the rare American city where the roof spends half the year completely untested and the other half taking everything at once. Most of the housing is older than the rest of California by a wide margin, a lot of it is flat rather than pitched, and the houses sit wall-to-wall with no side yard for a crew to work from. On top of that, California regulates who is allowed to do roofing more tightly than it regulates almost any other trade, and the city will not issue your permit to someone who does not hold the right licence. Here is what a San Francisco homeowner actually needs to understand before calling anyone.
Your roof is not tested between June and September
Under NOAA's 1991–2020 normals, the downtown San Francisco station averages 0.01 inches of rain in July and 0.06 inches in August. Add June and September and the entire four-month stretch comes to about a third of an inch. December alone averages 4.76 inches.
That is the single most important thing to understand about a roof in this city. A San Francisco roof can have an open seam, a failed flashing joint or a cracked membrane all summer and give you no sign whatsoever, because nothing is asking it to keep water out. Homeowners read that silence as a roof in good condition. It is not evidence of anything.
The practical consequence is about timing. The right moment to have a roof looked at here is September or October, while the weather is still dry enough to work in and before the first real storm finds the defect for you. Waiting until you see a stain on the ceiling means you are hiring in the middle of the wet season, competing with everyone else who waited, and paying for an emergency instead of a planned repair.
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When the rain does come, it arrives concentrated
The same normals put San Francisco at 22.89 inches of precipitation a year spread across roughly 71 days. That is a modest annual total delivered in a small number of sessions, heavily weighted to December and January, and it behaves nothing like a climate that rains a little most weeks.
A roof that leaks here usually does not start as a slow drip that gets gradually worse. It holds, holds, holds, and then fails during one storm, often the first significant one of the season. That is also why San Francisco roofers get busy in a narrow window and why quotes taken in December tend to be worse and slower than the same quote taken in September — the demand is compressed into the same weeks the weather makes the work hardest to do.
A great many San Francisco roofs are flat, and that is a different trade
Census figures put roughly 44 percent of San Francisco's housing at pre-1940 construction, one of the oldest housing stocks of any large American city. A lot of that stock — the Victorians and Edwardians of the Mission, the Richmond, the Sunset, Noe Valley, Bernal Heights — carries a flat or very low-slope roof behind a parapet or a decorative front cornice, often invisible from the street.
Low-slope roofing is a different system from pitched shingle roofing, not a variation on it. It is a membrane — torch-down modified bitumen, single-ply, or a built-up assembly — and it fails in different places: at seams, at penetrations, at the parapet wall junction, and anywhere water sits instead of running off. Drainage is the whole game, and a scupper or internal drain blocked with debris will pond water on a roof that was otherwise fine.
If your house has a flat roof, the crew you want is one that does flat roofs regularly, not a shingle crew taking one on. Ask what membrane they propose and why, how they will handle the parapet junction, and where the water is going to go. A quote that names a product and no drainage plan is describing half the job.
No side yard changes the job, and the price
San Francisco row houses sit on narrow lots, wall to wall, frequently with the garage at the street and a steep hill on one side of the block. There is nowhere to park a dumpster, nowhere to stage material, and often no way to get the old roof down except through the front or over the top.
This is not a detail — it is a real part of what a San Francisco re-roof costs, and it is the reason quotes between two otherwise similar houses can differ substantially. A contractor who has looked at your actual block will say something specific about access, street permits for a debris box, and where the crew will work from. One who quotes your square footage without ever mentioning how they intend to get material onto the roof has not finished pricing the job, and the gap tends to reappear later as a change order.
California licenses roofers specifically, and San Francisco enforces it at the permit
Roofing has its own licence classification in California: C-39, issued by the Contractors State License Board. You can look any contractor up by name or licence number on the CSLB website before you sign anything, and it takes about a minute.
There is a second thing worth knowing that most homeowners never hear. Under Business and Professions Code section 7125, C-39 roofing contractors are required to carry workers' compensation insurance whether or not they have employees. Roofing is one of a short list of classifications that cannot file the no-employee exemption most trades can. So on a roofing job in California there is no legitimate version of “it is just me, I do not carry comp.” If someone tells you that, the CSLB lookup will show it, and what it means for you is that an injury on your roof could become your problem.
The city closes the loop at the permit desk. San Francisco requires a permit before roofing material is installed, repaired or removed, the Department of Building Inspection issues it, and a contractor must hold a valid C-39 to apply for a reroofing permit online. Published fees start at $514 for single-family homes and duplexes and $714 for other building types, with project-specific fees on top — worth confirming with DBI directly, since municipal fee schedules are rarely the newest thing on a city website. Pulling it is the contractor's job. A roofer who offers to skip the permit to save you money is proposing unpermitted work on your house, and it will surface when you sell.
ZIP codes we cover in San Francisco
94102, 94103, 94104, 94105, 94107, 94108, 94109, 94110, 94111, 94112, 94114, 94115, 94116, 94117, 94118, 94121, 94122, 94123, 94124, 94127, 94128, 94129, 94130, 94131, 94132, 94133, 94134, 94158, 94188
Common questions
My roof has been fine all summer. Does that mean it is in good shape?
Not necessarily, and in San Francisco specifically it means very little. July and August here average almost no rain at all under NOAA's 1991–2020 normals, so a roof with a real defect has had nothing to reveal it. A dry summer is not a clean bill of health — it is just a season with no test in it. If the roof has not been looked at in years, early autumn is the moment to do it.
How do I know whether my roof is flat or pitched? I cannot see it from the street.
A great many San Francisco houses have a front cornice or parapet that hides a flat or nearly flat roof behind it, so the view from the sidewalk tells you very little. If you can get into the attic or onto an upper floor and the ceiling is close to level with no visible slope above it, that is a strong hint. Otherwise any contractor doing a real inspection will tell you on the first visit — and it matters, because flat and pitched roofing are genuinely different systems.
Do I need a permit to replace my roof in San Francisco?
Yes. The city requires a permit before roofing material is installed, repaired or removed, and the Department of Building Inspection issues it. Your contractor pulls it, not you, and to apply for a reroofing permit online they must hold a valid California C-39 licence. Published fees start at $514 for single-family homes and duplexes; confirm the current figure with DBI, since fee schedules change.
How do I check that a San Francisco roofer is legitimate before I sign?
Look the company up on the Contractors State License Board website and confirm it holds an active C-39 roofing classification. While you are there, check the workers' compensation status — under Business and Professions Code section 7125, C-39 contractors must carry it even with no employees, so a roofer showing an exemption is showing you something that should not exist. If the licence does not come back active, or the name on it does not match the company on your quote, that is the end of the conversation.
When is the best time of year to get roof work done here?
Late summer into early autumn. The weather is dry enough to open a roof safely, the wet season has not started, and contractors are not yet working through a backlog of leaks. September and October are also, conveniently, the warmest part of the San Francisco year. Waiting until the December storms means hiring at the worst moment on both price and availability.
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