A stain that appeared after the last Pacific storm. A flat roof over the back rooms that finally quit. A steep Victorian slope that has run out of years. Send the details and one vetted, licensed San Francisco roofer answers you. Repair or replacement, straight.
Useful things to tell us: when it started, where it shows up inside, roughly how old the roof is, and whether the trouble is over the steep front or the flat back.
No callback roulette. No five contractors buying your phone number.
Your house has two roofs
Start here, because almost every bad San Francisco roofing decision traces back to not knowing it.
Look at your building from the sidewalk and you see a steep, handsome, pitched slope. Victorian or Edwardian, composition shingle over it now, whatever it was originally. That is the roof you think you have. Behind it, invisible from the street, is a low-slope or dead-flat roof covering the rear rooms, the light well, and the back deck. Torch-down modified bitumen, usually. Sometimes TPO. Sometimes a built-up tar-and-gravel roof that has been patched by six different people.
Two roofs. Two materials. Two lifespans. Two crews, often. And the leak is nearly always in the one you cannot see.
So here is the opinion, and it will not please anyone selling you a beautiful front slope: spend your money on the back. The steep front sheds water by geometry and will forgive a lot of neglect. The flat rear is holding water on purpose, at seams, at drains, at the flashing where it dies into a stucco wall. That is where the failures are. If a roofer quotes your building without going around back, you have learned something about the roofer.
Moisture, not sun
Inland roofs die of heat. The sun cooks the asphalt, the granules wash off, and after twenty summers the shingle is a brittle cracker. That is not what happens here.
San Francisco roofs die of water and time. Fog and the marine layer mean a north-facing slope in the Sunset can go weeks in summer without ever fully drying, and what grows there is moss, algae, and lichen. Moss is not cosmetic. It lifts the shingle edge, holds a wet sponge against the roof deck, and works the nail line loose. Then in December an atmospheric river arrives sideways at 40 mph and finds every detail that moss quietly compromised in July.
West of Twin Peaks, in the Sunset and the Richmond, add salt. It eats galvanized flashing, fasteners, and vent collars from the outside in. A roof out there can have a sound field of shingle and completely rotten metal, which is a maddening failure mode because the roof looks fine and leaks anyway.
One more thing, since it saves people real money: do not let anyone pressure wash your roof. It strips granules, drives water under the courses, and takes years off the shingle. Soft wash, or nothing.
What the city adds to the bill
Access is a line item here in a way it simply is not in Elk Grove. No driveway. No place to stage a dumpster. A three-story walk-up whose roof is reached through the building or off the street, on a block where the crew cannot park. That is real money, and an honest estimate says so out loud rather than burying it.
Reroofs pull a permit through the Department of Building Inspection. If you are in a landmark district, or the building itself is designated, expect additional review that can constrain what the roof is allowed to look like from the street. Title 24 cool-roof rules apply to most low-slope reroofs, which is another reason the flat rear roof is not the simple part of the job.
And in a stacked flat or a two-unit Edwardian, a roof leak is not one household’s problem. Water enters at the top and turns up two floors down, in somebody else’s ceiling.
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Common San Francisco roofing questions
The stain is over the back bedroom. Is that the flat roof?
Probably. Membrane seams, the drain or scupper, and the flashing where the flat roof meets a wall or parapet account for most of it.
But do not assume the stain marks the hole. Water lands on the deck, runs along a rafter until it hits a nail or a joint, and drips there. The failure can easily be eight feet away and uphill. This is why “we patched right above the stain and it still leaks” is one of the most common calls we get.
What does a new roof cost here?
2026, typical single-family Victorian or Edwardian. Architectural asphalt on the steep sections: $16,000 to $30,000. Low-slope membrane over the rear rooms and decks: $9,000 to $22,000. Standing-seam metal on visible slopes: $28,000 to $60,000.
If your building needs both systems, it is two jobs and it prices like two jobs. City labor, no staging, and steep multi-story access are why these numbers look nothing like the suburbs. Ranges, not quotes.
Should I let them shingle over the old roof?
No. An overlay is false economy. It buries whatever is rotting underneath, adds dead load to old framing, and voids most manufacturer warranties. It also guarantees that the next roofer has to tear off two layers instead of one, and charges you for it. Tear off, look at the deck, then reroof.
How do I know the roofer is legitimate?
Check the C-39 on the CSLB site yourself. It takes a minute. Then look at the estimate: it should name the actual manufacturer and product line, not “30-year shingle” or “flat roof coating,” and it should describe both roofs on your building. Anyone who quotes without going up top, or who tells you the price expires tomorrow, has told you what you need to know.
How long will the crew be here?
Three to six days for a composition reroof, two to four for flat membrane work, one or two for most flashing and seam repairs. Both systems at once, longer. The real schedule risk is not labor, it is rain: between roughly November and March the job is scheduled around storms, and a good roofer will dry you in and wait rather than lay a membrane onto a wet deck.
Send your San Francisco roofing details
Most of what we see turns out to be a repair. A flashing leak. A failed seam over the back rooms. A few slipped shingles after a storm.
Tell us the roof’s age, when the problem started, and what it is actually doing: dripping, staining, ponding on the flat section, missing pieces since the last storm. Specifics turn a guess into an estimate.
No cost, no obligation. Just a read from the roofer who would do the work.