Who Says Waterproofing Has to Be the Unsexy Hero of San Francisco Homes?
We’re here to change your mind, and show you why siding is more than just a pretty face.
5 minute read.
Waterproofing isn’t the kind of thing people brag about at dinner parties. You’ll hear plenty about a new kitchen backsplash or the perfect shade of white paint, but no one ever says: “Check out my rainscreen gap, it’s gorgeous.”
(Though if anyone ever did, it’d probably be us. There’s a quiet kind of pride in knowing those details are done right.)
And yet, it’s the part of your home that decides whether you live in comfort or in a damp, moldy money pit.
Here in San Francisco, where the fog rolls in sideways, the air carries salt, and many of the houses here were built back when horse-drawn carriages still clattered down the streets. Your exterior isn’t just decoration. It’s armor. And like any armor, it’s only as strong as its weakest seam.
With rainy season just around the corner, this is the moment to get real about what’s behind your siding, before water beats you to it!
Behind your siding
We’ve pulled off more siding than we can count, and behind it we often find the same story; rot, mold, patch jobs held together by caulk, good intentions, and hopeful wishes.
It’s rarely the homeowner’s fault. San Francisco houses have lived through decades of “temporary solutions” which mean a strip of wrap here, a patch of siding there, a bead of caulk to get through another season. It works… until it doesn’t.
Water intrusion is patient. It finds the tiniest weak spot and settles in. By the time you notice stains or feel a soft patch inside, water has already been running its own remodel behind the walls.
If that sounds familiar, you’re not alone. Most older SF homes have some version of this. The trick is making sure your home doesn’t keep repeating the same cycle.
The Anatomy of Proper Waterproofing for SF conditions (in our experience)
We could talk about membranes and rainscreens all day, but it’s easier to show you.
On a recent project on Washington Street, we peeled back the siding on a home that had gone through years of deferred maintenance. What we uncovered was textbook; severe dry rot, mold, and framing that had been quietly compromised by decades of water intrusion. A cautionary tale, but also the perfect case study.
Here’s how we rebuilt the exterior for longevity, layer by layer:
The first step was structural.
We replaced all compromised framing members with new lumber, carefully tying into the original framing that was still solid. Only then could we start rebuilding the protective layers.
The Base.
Continuous plywood sheathing created a clean, solid canvas (as opposed to the uneven framing often found in SF homes) and added seismic strength. We meticulously created cut outs in the plywood for windows, doors and other openings.
The Weather Barrier.
Instead of a loose wrap like the industry standard Tyvek, we installed a fully-adhered waterproofing membrane (the blue material) that bonds directly to the sheathing and self-seals around any nails, fasteners, or punctures. This membrane is a continuous, monolithic protection as opposed to a wrap like Tyvek.
Around Openings.
Windows and doors are notorious leak zones, so we used a liquid-applied flashing that cures into an impenetrable, flexible shield, and completes the continuous membrane.
Roof + Wall Tie-Ins.
At rooflines and wall junctions, we bridged the layers with specialized flashing to lock everything together like armor plates. Bump outs or other architectural details, like bay windows common in SF homes, are notorious for poor waterproofing and leaks if not tied in properly to the adjacent areas. There are many layers of waterproofing in just this bump out of bay windows alone!
The Rainscreen system.
Those black mesh-looking strands create a slim gap between your siding and waterproofing membrane that lets walls drain and breathe. Think of it as lungs for your house.
Siding + Metal Flashing.
Finally, new siding went up, finished with custom sheet metal flashing to redirect water away from trims and joints. The part you see, backed by layers you don’t.
None of it is necessary glamorous. But each layer adds up to the difference between a home that quietly soaks in San Francisco’s fog and one that plays a moisture fighting dance with it.
Intentional & Regular maintenance offers peace of mind
A few simple habits can keep water where it belongs:
Repaint at least every 5–7 years (paint is your home’s first line of defense).
Replace whole walls when the time comes to address a trouble area. Patch jobs (or worse, caulking) in your waterproofing membrane just invite water to find a seam.
Keep gutters and roof drains clear (SF roof decks are especially guilty of flooding themselves).
Don’t let soil pile up against your siding as it’s basically an open invitation for moisture.
Wash exterior wood with a diluted bleach solution to keep mold from moving in.
None of this is exciting, but your future self (and your house) will thank you.
Why Now Is the Time
Right now, the weather’s dry. That makes this the sweet spot for exterior work. Once the storms arrive, opening up walls isn’t just inconvenient, it’s risky.
And waiting is always an option. Many people put it off, hoping things will hold up another season. But what we see too often is that the first sign of trouble inside means water has already been at work for a long time behind the walls. By then, the repair is never as simple as it could have been.
The best time to take care of siding and waterproofing is when the weather is dry and predictable. That way, walls can be opened up, repaired, and closed again without the risk of sudden storms interrupting the process.
Not Exactly Instagrammable, But Essential
Most people will never see the layers we put behind siding, and honestly, that’s the point. If no one notices, it means the home is doing its job.
Our satisfaction comes from knowing a house is sealed, dry, and set up for another century of fog and rain. We’ve learned these lessons by opening up plenty of homes that didn’t get it right the first time and by putting them back together so they can stand strong again.
It may not be glamorous, but in San Francisco, that’s our idea of a sexy hero.
Exterior Check-Up
Most people never think about waterproofing until they have to. We think about it so you don’t have to. We’ve seen what happens when water sneaks in and we’d rather catch it early. Reach out if you’d like us to take a look at your siding before the rains roll in.
