A stain creeping across the ceiling. A drip that only shows in a storm. Water turning up in the unit downstairs. Send a few details and one vetted, licensed San Francisco roofer gives you a straight read on what it takes to find and stop it.
Tell us where the water shows up inside, whether it tracks with rain or wind, and the roof type. The spot you see the drip is almost never where the water gets in.
The drip is not the leak
Finding a San Francisco roof leak is the hard part. Fixing it is often twenty minutes of work once you know where it is. Water gets in at a failed flashing, a split seam, or a lifted shingle, then runs along the underside of the sheathing or down a rafter until it meets a nail or a joint and finally drops. By then it can be eight feet from the hole, and uphill. A Noe Valley stacked flat makes this worse: water that enters above one unit routinely stains a ceiling two floors down, over a room that has nothing to do with the actual breach.
Patch the stain and you have just repaired the one part of the roof that wasn’t leaking. Pay someone to trace the water, not to guess at it.
When the leak happens tells you a lot before anyone climbs up. A drip that only appears in a hard, wind-driven Pacific storm usually means rain is being pushed sideways past flashing or under a shingle course. That is not a hole. A leak that shows in any steady rain points somewhere else: a worn membrane, a clogged drain backing up, a seam that has let go on the flat rear roof. Two different searches. Telling us which one you see narrows it fast.
Where the water usually gets in
On the city’s two-roof homes, the front steep slope sheds water and rarely leaks. The trouble lives on the flat rear roof and at every transition between the two. Here is where an SF roofer looks first, and the rough cost of the fix once the source is confirmed.
| Entry point | What you notice inside | Typical repair (2026) |
|---|---|---|
| Flashing where the steep front meets the flat rear | Stain over the back rooms, worse in wind | $450–$1,500 |
| Parapet wall cap cracks (rear and deck roofs) | Damp high on an interior wall, not the ceiling | $600–$2,500 |
| Split seam or clogged drain on the flat roof | Spreading stain after any steady rain | $500–$3,000 |
| Chimney, skylight, or vent penetration | Drip near a fixed object, every storm | $400–$1,800 |
| Lifted or brittle shingles on the steep slope | Occasional drip only in wind-driven rain | $350–$1,200 |
The tell that the source is actually found
A roofer who has found the real entry point can show you the path: here is where it comes in, here is the rafter it rides, here is where it drops. If the answer is “we sealed around the stain,” the leak will be back with the next storm. In the rainy season, roughly November through March, the right first move is a dry-in that stops the water now, then the permanent repair on a dry window once the deck is dry enough to bond to. A sealant laid over a wet TPO or modified-bitumen seam does not hold. It just buys a callback.
Common questions
Can you fix a leak while it’s still raining?
We can usually stop it with a temporary dry-in. A lasting repair needs the roof dry, because patches don’t bond to a wet surface. Anyone promising a permanent fix in the middle of a storm is setting you up for a second visit.
The leak only happens in a big storm. Why can’t you find it on a dry day?
Wind-driven leaks are the trickiest kind. When a strong Pacific storm pushes rain sideways, it gets past flashing and under shingles in ways that calm vertical rain never does, so on a still, dry day there is nothing to see. Finding these means reading the entry points the wind exploits: the windward flashing, the exposed seams, the upwind edges. Sometimes it takes a controlled water test aimed to mimic the storm direction. That is why the wind direction during the leak is one of the most useful things you can tell us.
Water is showing up in the unit below mine. Is it my roof?
Maybe, maybe not. In a stacked flat, water that enters the roof can run along the framing and drop into a unit well away from the entry, sometimes across what feels like a boundary between homes. It has to be traced back to where it actually gets in, so the fix lands in the right place and the right party knows what is involved.
Send your San Francisco roof leak details
Tell us where the water shows up inside, whether it tracks with storms or wind direction, and the roof type. You’ll get a straight read on what it takes to trace and stop the leak, with no pressure to book.
No cost, no obligation. Just a clear answer from the roofer who’d actually do the work.