Roof at the end of its life, one too many patches on the flat section, or a leak that keeps coming back no matter what? Send a few details and you’ll get a straight answer on whether it’s genuinely time to replace — and what a real replacement should cost — from one vetted, licensed San Francisco roofer.
Tell us the age of the roof, whether the trouble is the steep front slope or the flat back roof, and what’s been done to it so far. That’s what separates an honest replacement recommendation from an oversold one.
When a San Francisco roof actually needs replacing
Plenty of San Francisco roofs get quoted for replacement when a roof repair would do. A roof genuinely earns a full replacement when the failures are spread across the roof rather than at one detail, when the membrane on the flat section is at the end of its service life, when repeated patches have stopped holding, or when the underlayment beneath the shingles has broken down. The tell is whether a roofer can show you the widespread failure — photos, moisture readings, lifted sections — or is simply asserting that the roof is “shot.”
Because most SF homes carry both a steep front slope and a flat rear roof, replacement is rarely all-or-nothing. It’s common and completely legitimate to replace the flat roof over the back rooms while the front slope still has years left, or the reverse. A good roofer prices the two systems separately and tells you which one is actually done — not just packages the whole building because it’s easier to sell.
What a replacement involves here
- Tear-off and inspection — removing the old roof down to the deck and checking the sheathing and framing, which on a pre-1940 building can hide dry rot around old leaks.
- New underlayment and flashing — the parts that actually keep a fog-and-storm city dry; skimping here is why cheap reroofs leak within a few winters.
- The right system for each section — architectural composition or standing-seam on the steep slope, torch-down modified bitumen, TPO, or built-up membrane on the flat.
- Drainage and detailing — scuppers, drains, deck-to-wall and parapet flashing done properly so water leaves the roof instead of sitting on it.
- Permit and cleanup — a DBI permit, Title 24 compliance on low-slope work, and hauling debris off a street with nowhere to park.
Common questions
What does a roof replacement cost in San Francisco?
As of 2026, an architectural asphalt shingle reroof on the steep sections of a typical SF home runs roughly $16,000 to $30,000, a flat torch-down or TPO roof over the back $9,000 to $22,000 depending on size and access, and standing-seam metal on visible slopes $28,000 to $60,000. City labor, no on-site parking, steep multi-story access, and buildings needing both systems at once push costs above suburban norms. A real quote depends on square footage, pitch, access, and how much deck repair turns up at tear-off.
Can I put a new roof over the old one?
Sometimes on a steep composition slope, but it’s usually a false economy here. An overlay hides the condition of the deck and old flashing — exactly the things that leak in a moist, storm-driven climate — and it doesn’t let anyone find dry rot in older framing. On flat roofs, going over a failed membrane rarely lasts. Most of the time a proper tear-off is the honest, longer-lived choice, and a roofer should explain why rather than just quoting the cheapest option.
How long does a replacement take?
A steep composition reroof is typically three to six days on site, and a flat-roof membrane two to four, weather permitting. A building that needs both is effectively two jobs and runs longer. The bigger variables in the city are the winter rain window and access — staging materials and hauling debris on a street with no parking adds time that a suburban job wouldn’t.
Send your San Francisco roof replacement details
Tell us the age of the roof, which section is failing, and what’s been patched already — and you’ll get a straight read on whether it’s truly replacement time and what it should cost, with no pressure to book.
No cost, no obligation — just a clear answer from the roofer who’d actually do the work.