Quick answer
Rowhouse gutters and scuppers in San Francisco: Most San Francisco rowhouses have a flat or low-pitched roof that drains through a scupper, a short gutter and one or two leaders, so a single clogged outlet can pond water on the roof or send it down the cornice and siding. Keep those few outlets clear before the November rains, make sure each leader runs freely all the way down, and plan ladder access ahead of time, because there is usually no side yard to work from. Call (650) 600-0598 or get a free quote.
Flat roofs, few outlets
How water leaves a San Francisco rowhouse roof
A rowhouse roof does not have a gutter running around all four sides. It has a few outlets, and each one matters.
A lot of San Francisco’s housing predates the war, and it shows at the roofline. In ZIP 94114, U.S. Census Bureau figures show 61 percent of housing units were built in 1939 or earlier. Noe Valley filled in with Victorians from the 1870s on and Edwardians after 1906, and many of those false fronts hide a low-pitched roof. In the Sunset, builders covered the dunes with stucco homes on 25 foot lots from the 1920s through the 1940s, many with red tile trim along the front and a low-slope roof, first built as tar and gravel, behind it.
Rain leaves those roofs through only a few openings. There is usually a scupper, an opening at the roof edge, feeding a short gutter or dropping straight into a leader, which is the downspout. There may be a short rear gutter and an inside corner. A scupper and one leader can be doing the work a whole run of K-style gutter does on a Peninsula ranch house.
Then the water goes underground. According to the San Francisco Public Utilities Commission, San Francisco is the only coastal city in California with a combined sewer system, and stormwater enters it through building roof drains and street catch basins. Roof water and household wastewater share the same pipes, so a leader clog can sit below ground where you cannot see it.
One outlet is the whole system
When a flat roof drains through one outlet, that outlet is the entire system. If it clogs, the water does not wait. It ponds on the roof or finds another way down: over the cornice, down the stucco or into the wall. Get that one outlet wrong and the water goes straight into the cornice.
That is also why a rowhouse can look fine for months and fail in a single night. The roof is dry from late spring into fall, grit and leaves collect around the scupper, and the first heavy storm pushes all of it toward one opening at once.
What we find
Where scuppers and leaders fail
Rowhouse drainage tends to fail at the same few spots. Where the water shows up in a storm points to which one.
Most of these show up during or right after rain, so look from the sidewalk or a window while it is still coming down.
| What you see | Likely cause | Usual fix |
|---|---|---|
| Water standing on the roof after the rain stops | Scupper or roof outlet blocked with grit, needles or leaves | Clear the scupper and flush the leader all the way through |
| Water running down the front wall or cornice | Outlet clogged or too small, so water finds the low edge | Clear it, then size the outlet and leader for the roof area |
| Drips or stains at the back of the house | Short rear gutter pitched the wrong way or leaking at a seam | Reset the slope, reseal, or replace with a seamless gutter |
| Leader spilling at its joints | A clog lower down, often at an elbow | Flush from the top; a clog below ground is a job for a plumber |
| Rust streaks and pinholes | Old galvanized steel worn by salt air | Replace with aluminum or copper |
| Water pouring into the light well | Leader disconnected, cracked or crushed | Reattach or replace the damaged section |
Fog turns debris into sludge
Fog and wind are the local story here. On the west side, summer fog drips steady moisture into gutters for months, so wet debris and roof grit build up in the trough and at the seams. Debris that never dries turns to sludge and holds water against the gutter and the wood behind it. The ocean wind adds its own trouble, pushing runoff past a short gutter lip and loosening hangers and leader straps. Just south in Daly City, the fog belt keeps needles, grit and debris wet year round on shaded north-facing runs.
What lands on your roof depends on the block
Homes near Sunset Boulevard and along Lincoln Way by Golden Gate Park catch needles from the Monterey pines and cypress. Eucalyptus bark and litter come down near Mount Sutro, the Presidio and Stern Grove. In Noe Valley, southern magnolia is the most common street tree on the city’s Street Tree List, ahead of swamp myrtle and flowering cherry, and those big leathery leaves lie flat over an outlet like a lid. Out toward Ocean Beach, the wind packs sand into gutters and scuppers.
Shared walls
No side yard: working around shared walls and light wells
On a rowhouse, the hardest part of a gutter job is often getting to the gutter.
Victorian and Edwardian rowhouses share walls with the neighbors on both sides, so there is no side yard to set a ladder in and nowhere obvious to run a leader except the front steps or the light well. Narrow side gaps and small rear yards are normal in the Sunset and Parkside, where many homes have a short gutter across the front, a flat or low-slope roof behind it and a single leader that drops past the garage door to the sidewalk. Some attached homes even share a downspout with the house next door.
That is why access gets planned on the walkthrough, not argued about on the day. A Solutionist looks at where a ladder can safely stand, how to reach the rear gutter, and whether the leader you care about also carries part of your neighbor’s roof. Shared downspouts get noted in the written scope, so everyone knows what is being touched. On the day, the crew bags the debris and carries it out, so nothing ends up in the light well or on a neighbor’s roof.
Talk to your neighbor first
- Whether you share a leader, a gutter or a roof outlet at the property line.
- Which way the roof between your two houses drains.
- Whether a ladder needs to stand in their yard or on their side of the light well.
- Any leaks or stains they have noticed on their side of the shared wall.
- When their own outlets were last cleared, since a shared edge drains both roofs.
Sorting this out ahead of time makes for a quicker visit and fewer surprises.
Fog, salt and storms
Keeping a rowhouse roof draining all winter
With so few outlets, a little attention at the right time goes a long way.
San Francisco gets noticeably more rain than Sunnyvale, and it arrives in a short, heavy season. NOAA’s normals for the San Francisco Downtown station put the average at 22.89 inches a year, with about 84 percent of it falling from November through March. Many of the biggest storms are atmospheric rivers, which is why our rain-ready checklist for Peninsula homes pushes the work into October.
- Clear scuppers and outlets in fall.The Sunset’s clearest weather usually runs from September into early November, the best window to clean and fix before the storms.
- Flush every leader.Run water in from the top and confirm a steady stream comes out the bottom. A slow leader means a clog at an elbow or below.
- Check the street end.If the curb drain out front is buried in leaves, report it to 311 under catch basin maintenance, as the SFPUC asks.
- Look at the metal.Rust streaks, pinholes and loose straps on old steel gutters and hangers mean salt air has been at work.
- Watch the first big storm.Note where water escapes, then get it on the list for when the weather clears.
Repair, replace or guard
A loose leader strap, a leaking corner or a short gutter pitched the wrong way is usually a gutter repair, done in one visit when possible. When old galvanized runs are rusting through, replacement makes more sense. Aluminum and copper hold up far better near the ocean than old galvanized steel, and we form them on-site as a seamless gutter cut to the exact length of the run. For a Victorian or Edwardian front, copper gutters are worth a look.
Where trees or wind-blown grit keep filling the outlets, BroGuard stainless micro-mesh keeps that grit and debris out while the water runs straight through. A scupper with no trees nearby may only need regular cleanings. Our gutter maintenance program puts those cleanings on the calendar ahead of the storms, and every gutter cleaning includes clearing the scuppers and flushing the leaders, not just the trough. See how we work across the city on our San Francisco page.
Want someone to look at your scuppers and leaders before the storms? Call (650) 600-0598
Get a Free QuoteFrequently Asked Questions
A scupper is an opening at the roof edge that lets water off a flat or low-pitched roof, usually into a short gutter or straight into a leader, the downspout below it. On many rowhouses a scupper and one leader do the work a whole gutter run does on a pitched roof, so if that one opening clogs, water ponds on the roof or runs down the wall.
Usually the scupper or roof outlet is partly blocked with grit, needles or leaves, or the leader below it is clogged at an elbow. Clear the opening and flush the leader from the top. If water still backs up after that, the clog may be farther down the line, below ground, where a plumber is the right call.
Yes. Attached houses with shared walls, light wells and no side yard are regular work for our crews. A Solutionist plans the ladder setup and access during the free walkthrough, and the crew bags the debris and carries it out, so nothing ends up in the light well or on a neighbor’s roof.
Aluminum and copper hold up far better near the ocean than old galvanized steel, because salt air works on steel gutters, hangers and fasteners. We form aluminum and copper gutters on-site to the exact length of each run, so the only seams are at corners and outlets, which leaves fewer joints for wet fog and salt to work on.
According to the SFPUC, San Francisco is the only coastal city in California with a combined sewer system. Stormwater enters it through building roof drains and street catch basins and is treated along with household wastewater. That means a clogged leader can back up below ground, and a street drain blocked with leaves should be reported to 311.
Free quotes
Ready to get your rowhouse roof draining before the next storm in San Francisco?
Free, no-pressure written estimates from your local crew, based in Sunnyvale and working across San Francisco. Scuppers cleared, leaders flushed and tested, and access planned before anyone climbs a ladder.
The Brothers That Just Do Gutters · Sunnyvale · (650) 600-0598 · Serving Sunnyvale, CA and the Peninsula, from Santa Clara to San Francisco