Cedar siding and trim rot on Eastside homes because dry-rot fungi need wood, mild temperatures and moisture — and western Washington supplies moisture for roughly eight months a year. The usual root cause is not the cedar itself but flashing done wrong: missing kickouts, reversed laps, or failed caulk joints that route water behind the siding. Caulking or filling over rot never holds, because the fungus stays alive in the surrounding fibers.
You pressed a finger into the trim under a window and it felt spongy. Or maybe you noticed the fascia board looks dark and swollen, and now you're wondering how far the rot goes and whether the whole side of the house is compromised. If you're on the Seattle Eastside, you're not alone — dry rot is one of the most common problems we get called out for, and the honest answer is that our weather here will beat up the wood if it isn't protected properly.
The short version: rot is a fungus, and fungus needs moisture, mild temperatures, and wood to eat. From October through May, the Eastside gives it all three in generous supply. Our rain isn't a downpour that runs off and dries out — it's weeks of drizzle, fog, and damp air that keeps wood wet long enough for fungal spores to take hold.
"Dry rot" is a bit of a misleading name. The wood was wet when the fungus got started; it just looks dry and crumbly by the time you find it. By that point, the fungus has already digested the fibers that give wood its strength, which is why rotted trim breaks apart in your hand instead of splintering.
Cedar is naturally more rot-resistant than most woods, which is why so many homes here were sided with it. But "resistant" isn't "immune." Once the finish fails, once water gets behind a board, or once a piece sits in constant contact with moisture, even good cedar will go.
After eight recent visits involving rot, a pattern is clear. The trouble spots come up again and again:
Flashing is the thin metal that directs water away from joints — around windows, doors, rooflines, and where siding meets other materials. When flashing is missing or installed backwards, water gets in and can't get out. It sits behind the siding, invisible, feeding rot for years before a soft spot ever shows on the surface.
One homeowner we visited had paid a prior contractor for work and later found out they "didn't do the flashing like they needed to." From the street, everything looked fine. Behind the siding, water had been coming from a couple of different spots for who knows how long. That's the frustrating part of flashing failures: the quality of installation is invisible until the damage isn't.
This is why we tell neighbors to weight the quality of installation heavily when comparing bids. A cheaper job that skips proper flashing doesn't save you money — it just delays the bill and adds interest in the form of hidden water damage.
We understand the temptation. Rot repair isn't cheap, and a tube of sealant is. One homeowner we met had tried a DIY sealant over rotted trim, and it failed the way it always does — the fungus kept working underneath, the wood kept softening, and water found its way in around the edges of the patch.
Here's the thing about rot: it spreads. The fungus sends threads into wood that still looks solid. If you cut out only the visibly bad section, you often leave infected wood behind, and the rot marches on. One of our clients put it perfectly: "if there is rot, it all has to go." That's our rule too. Proper dry rot repair means:
Do it once, do it right. Patching rot is how you pay for the same repair twice.
We won't quote numbers in a blog post, because honest pricing depends on what we find. But we can tell you what moves the needle, so there's transparency and no last-minute surprises:
If budget is tight, tell us. We can help you prioritize — get the stuff that is very important handled first, keep the costs you can control low, and plan the rest before the weather turns.
Press on suspect areas with a screwdriver handle or your thumb. Sound wood is firm; rotted wood feels spongy, soft, or crumbles. Also look for paint that's bubbling or peeling in one area, dark staining, and swollen or cracked boards — especially under windows and along the bottom of walls.
Yes. The fungus travels through wood beyond what you can see, which is why partial patches fail. If rot in siding or trim reaches the sheathing or framing, the repair gets bigger and more urgent. That's the reason all affected wood has to go.
Ideally, yes. Open or softened wood takes on water fast once the fall rains arrive, and damage accelerates over winter. If a full repair isn't possible before the weather turns, a proper temporary weatherproofing can help the house make it to spring — but it should be a plan, not a patch you forget about.
Almost certainly. Inspectors probe trim, fascia, and siding, and rot is one of the most commonly called-out items in our area. If you're planning to sell, handling it proactively — with everything called out, handled — is usually smoother than negotiating repairs with a buyer lined up and a clock running.
If you've found a soft spot — or you just want to confirm everything's solid before winter — we're happy to take a look. Roof4Life is a family-owned, licensed contractor (ROOF4778BL) serving Kirkland and the greater Seattle Eastside since 2012. We'll tell you plainly what needs attention now, what can wait, and what we'd recommend if it were our own house. Call (425) 207-3500 to get a free inspection booked and get it squared away before the rain settles in.
No-obligation, detailed written estimate from Roof4Life. Serving Kirkland, Bellevue, Redmond, Sammamish, Issaquah & the entire Seattle Eastside since 2012. Rated 4.9 stars across 74 reviews.
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