San Francisco Roofing Contractor for Fog, Flat Roofs & Winter Storms

Water coming through ceilings, walls or light fixtures during a heavy storm. It's usually caused by flashing that's pulled away at a wall, chimney or skylight, or by a blocked scupper or drain that lets water pond and back up under the membrane.

San Francisco's rain comes in a few intense bursts instead of steady drizzle. One atmospheric river can drop several inches in a day or two, often with strong westerly winds pushing water sideways into joints that stay dry the rest of the year. Months of dry weather let leaves, pigeon debris and windblown grit build up in scuppers and drains. Then the first big November storm hits a roof nobody has looked at since spring, and every roofer in the region gets booked up at the same time.

• Dripping or brown stains appearing during or right after rain
• Bubbling paint or sagging drywall on top-floor ceilings
• Water running down interior walls below parapets
• Standing water on a flat roof 48 hours after rain stops
• Overflowing scuppers or downspouts that aren't draining
• Musty smell in upper rooms or the attic

Flat-roofed Victorians in the Mission and Noe Valley, and Doelger homes in the Outer Sunset and Excelsior, see this most often. We usually trace it to parapet caps, scuppers and wall-to-roof flashing. Leak calls spike after the first big storm of the season.

Our fix: We tarp or seal the roof to stop water right away, clear the drains, find the actual entry point, then quote a permanent flashing, scupper or membrane repair in writing.

Wood decay in the roof structure: the spaced boards (skip sheathing) under old roofs, the fascia boards along the eaves, and exposed rafter tails. Rotted wood can't hold fasteners, so new roofing on top of it won't last.

Constant fog and marine moisture keep wood damp for much of the year, especially in western neighborhoods where the sun rarely dries out north-facing eaves. Many San Francisco roofs still sit on skip sheathing from the original wood-shingle era, with one or two layers of later roofing stacked on top that trap moisture. Overflowing or rusted-through sheet-metal gutters soak fascia and rafter ends. Most of this stays hidden until tear-off, which is why scope often grows once the old layers come off.

• Soft or spongy spots when walking the roof
• Fascia boards that are cracked, swollen or crumbling
• Paint peeling along eaves and gutter lines
• Sagging rooflines or wavy shingle rows
• Gutters pulling away from the house
• Daylight visible through attic boards

Common in the Outer Sunset, Inner Richmond, Glen Park and Daly City, where fog sits for days at a time. Pre-1915 homes in Haight-Ashbury and Bernal Heights often have skip sheathing that has to be overlaid with new plywood.

Our fix: We replace rotted boards and rafter tails, install new plywood decking over skip sheathing, and document hidden damage with photos before any change to the agreed scope.

Leaks from built-in gutters set into the roof edge, or from the tops and inside faces of parapet walls. When the lining, coping or counterflashing fails, water runs straight into the wall cavity and ceilings below, often far from the actual entry point.

Victorian and Edwardian builders hid roofs behind decorative false fronts and drained them through built-in box gutters. A century later, a lot of those gutter linings are rusted, patched with layers of tar, or sloped wrong after the building settled. Parapet caps crack from seismic movement and constant wet-dry cycles. Because these roofs can't be seen from the street, owners often don't find out until plaster stains show up two rooms away.

• Stains near exterior walls rather than mid-ceiling
• Cracked or loose parapet coping
• Rust stains or tar patches on gutter linings
• Efflorescence or bubbling stucco on parapet faces
• Water marks on cornices or below gutter outlets

Very common on Pacific Heights, Mission District and Noe Valley Victorians, and on shared parapets between Outer Sunset row houses, where the work has to be coordinated with the neighbors.

Our fix: We reline box gutters with new membrane or sheet metal, rebuild parapet caps with proper counterflashing, and correct slope so water reaches the scuppers.

Built-up tar-and-gravel and modified bitumen (torch-down) roofs that have reached the end of their service life. You'll see blistering, cracking, open seams, granule loss and ponding that keeps getting worse.

Because the city is so dense, flat and low-slope roofs are everywhere here. A lot of them were installed decades ago and patched many times since. In San Francisco, damp conditions break down seams and feed algae. Inland, in San Jose, Willow Glen and the East Bay flatlands, summer heat in the 90s and 100s dries membranes out and cracks them. Roof decks built straight over the membrane add foot traffic and make inspection hard.

• Blisters or bubbles in the membrane surface
• Cracks, alligatoring or bare spots without gravel
• Seams lifting at edges and laps
• Ponding areas that grow each season
• Repeated patches in the same areas
• Debris and vegetation growing in low spots

Doelger homes in the Outer Sunset and Daly City, Eichlers in Palo Alto and Willow Glen, and small apartment buildings across the Mission and Excelsior are near the end of their tar-and-gravel lifespan.

Our fix: We tear off down to the deck, correct drainage with tapered insulation or crickets, and install a Title 24-compliant cool membrane such as TPO, PVC or a modified system.

Water getting in where the roof meets a chimney, skylight or light well. Step flashing, counterflashing and curb seals separate, corrode or crack, and water runs down into framing and finished ceilings.

Many San Francisco chimneys are unreinforced masonry, and plenty were cracked or shifted in the 1989 Loma Prieta quake. Even small movement breaks the seal between brick and flashing. Salt air corrodes steel flashing, and old skylights and light wells were often sealed with mastic that dries out after a few years of sun and fog. These are some of the most common leak sources we trace.

• Stains on the ceiling or wall beside the chimney
• Water in the firebox or damp smell from the fireplace
• Rusted or tar-covered flashing
• Condensation or drips around skylight frames
• Cracked mortar or loose bricks at the roofline

Frequent in Bernal Heights, Glen Park and Rockridge homes with older brick chimneys, and in Victorians with light wells. Coastal homes need stainless or coated flashing.

Our fix: We install new step and counterflashing, reseal or replace skylight curbs, and flag chimney masonry concerns so you can have a structural or seismic review done.

Green or black growth on shingles, tile and shake, usually on north-facing or tree-shaded slopes. Moss holds water against the roof, lifts shingle edges and clogs gutters, which shortens roof life over time.

The persistent marine layer over western San Francisco and Daly City keeps roof surfaces damp for days at a time. Tree cover in the Oakland hills and the Peninsula adds shade and leaf litter. In Santa Cruz County, 30+ inches of rain a year and heavy forest debris make it worse. Left alone, moss turns a minor maintenance task into early replacement.

• Green or black streaks on roof surfaces
• Clumps of moss along shingle edges
• Gutters filled with organic debris
• Shingle tabs curling or lifting
• Dark, damp patches that stay after rain

North slopes in the Outer Sunset, Inner Richmond and Montclair, plus wooded parts of San Mateo and the Santa Cruz Mountains. Shake roofs in the hills are especially vulnerable.

Our fix: We remove growth gently without power-washing, clear gutters, treat surfaces, and recommend zinc or copper strips or algae-resistant shingles where it fits.

Shingles, ridge caps or drip edge that have been loosened, creased or blown off by wind. Once a few tabs lift, rain gets underneath them and the next gust pulls off more.

Strong westerly onshore winds hit exposed ridges and coastal neighborhoods all year, and Diablo winds occasionally sweep the East Bay hills. Shingles installed with too few nails, or with fasteners corroded by salt air, are the first to go. Heat cycling inland also weakens adhesive strips.

• Shingles or ridge caps found in the yard
• Creased or lifted shingle tabs
• Flapping or bent drip edge
• Exposed nail heads or underlayment
• New leaks after a windy storm

Twin Peaks, Glen Park ridges, Daly City and the Oakland Hills see the most wind damage. Ocean-facing Outer Sunset homes also suffer fastener corrosion.

Our fix: We replace damaged shingles and edge metal with corrosion-resistant fasteners at the correct nailing pattern, and seal ridges to resist wind uplift.