Roofing in San Francisco is mostly a flat-roof problem in a city that stays wet. Modified membranes, built-up surfaces, and older tar-and-gravel roofs sit behind parapets. Water leaves through scuppers and drains that clog with grit and with debris from roof decks. Fog keeps seams damp for long stretches. A hilltop house takes wind that lifts edges and drives water against a wall that was supposed to be above the weather. Bay windows and additions punch through the roof and create the joints that actually leak.
The surface can look boring and still be done. Blisters, open seams at a parapet, a pond that remains after the rain, or a soft feel under a roof deck are classic signs. Skylights on stairwells leak at the curb. Drains that sit high leave a shallow lake over a bedroom. Gravel holds moisture. A coating rolled over a wet, dirty membrane does not rebuild the roof. Access is its own issue: many of these roofs are reached by a tight hatch or by a neighbor's permission, and the work has to be planned around that, not around a wide suburban driveway.
Inside, follow the stain, then assume it traveled. Plaster ceilings show a ring far from the low spot outside. A deck above a bay window can dump water into the wall of the room below. Rot in the sheathing spreads under a membrane that still looks intact from the street. Gutters on the pitched sections of older houses, where they exist, fill with city grit. The fix is drainage, seams, and rotten wood, not a new color on a tired lid. Fog will test the work every week. A repair that only looks good in sunshine will not survive this climate.
Call with what the roof is made of and how water is supposed to leave it. Mention ponds, soft decking, stains below, or a scupper you cannot see daylight through. Say if a deck or a skylight sits on the same surface. The job is a San Francisco flat roof in constant damp, not a tile roof from a drier coast.
Call the number on this page.