Why Everything Rots in the Pacific Northwest — And How to Catch Dry Rot Before It Spreads

Wood rots quickly in western Washington because dry-rot fungi need wood, mild temperatures and moisture — and the Eastside supplies all three for roughly eight months a year. Rot starts first at deck posts near concrete, stair treads and stringers, fascia behind leaking gutters, window trim, and siding close to grade. You can test for it with a screwdriver: sound wood resists, rotted wood gives way under light pressure.

If you've lived on the Eastside for more than a few years, you know the feeling. You step on a deck board and it gives a little. You press a thumb into the window trim and it's soft. One homeowner put it bluntly: "everything rots, you have to keep painting these damn things." Another described a 31-year war against water — and honestly, that's about right for western Washington.

Why Wood Rots So Fast in Western Washington

Rot isn't bad luck. It's biology. The fungi that cause dry rot need three things: wood, moderate temperatures, and moisture. In Kirkland, Bellevue, Redmond and the rest of the Eastside, we hand them all three for about eight months a year.

Our rain isn't dramatic — it's persistent. Wood gets wet in October and doesn't fully dry until June. Add shade from evergreens, moss holding moisture against surfaces, and mild winters that rarely freeze hard enough to slow fungal growth, and you have close to ideal rot conditions. That's why a deck that would last decades in a drier climate can be pretty rotted here in ten or fifteen years if water gets in.

One more thing worth knowing: "dry rot" is a misleading name. The wood looks dry and crumbly by the time you notice it, but the damage was done while it was wet. Waterproofing is the main thing — everything stems from where water gets in and stays.

Where Rot Starts First on Eastside Homes

After thousands of inspections since 2012, we see the same trouble spots over and over:

• Deck posts at the base — especially posts set in or on concrete where water pools. Homeowners in Kirkland, Renton and Snohomish have all shown us posts that looked fine from five feet away and were compromised at the bottom.
• Stair treads and stringers — flat surfaces that hold water. If someone in your house is dreading those steps, trust that instinct.
• Fascia and rake boards — where gutters overflow or drip edge is missing, water runs behind and the board rots from the back side out.
• Window trim and sills — horizontal surfaces with failed caulk or paint. Soft trim is often the first visible sign of a bigger problem in the framing behind it.
• Siding near the ground — anywhere siding sits too close to soil, patios or splash-back from roof runoff.

How to Tell If Deck Wood Is Rotted

You don't need special tools — you need a screwdriver and ten minutes.

• Probe it. Press a screwdriver into suspect wood. Sound wood resists. Rotted wood gives way with light pressure, or the tip sinks in easily.
• Look for cubical cracking. Advanced dry rot breaks wood into small, brick-like chunks. That wood has no structural value left.
• Check paint that's bubbling or peeling in one spot. Paint failure in a single area usually means moisture behind it, not a paint problem.
• Notice movement. A railing that wobbles or a step that flexes underfoot means something structural is deteriorated. If it feels unstable to go down, don't wait for it to fail — it's telling you something.
• Follow the water. Find a rotted spot, then look up. Rot almost always starts where water enters above and travels down.

Targeted Repair or Full Replacement? The Honest Answer

We hear two extremes from homeowners. Some hope we can save these boards and do just the steps. Others assume "if there is rot, it all has to go." The truth is usually in between, and it depends on where the rot is — not how much you can see.

A targeted repair works when the rot is limited to non-structural, replaceable pieces: a few treads, a section of trim, one fascia board — and when we can fix the water source that caused it. Replacing rotted wood without fixing the leak means it's still leaking behind the new material, and you'll be back at this in two or three years.

Replacement makes sense when rot has reached structural members — posts, beams, ledger boards, framing behind siding. A rotted deck post can sometimes be replaced individually, but if the beam it supports is also soft, patching one piece is throwing money at a failing system. Same with siding: if the sheathing behind it probes soft, new siding over rotted sheathing is a cosmetic fix on a structural problem.

Cost-wise, the drivers are how deep the rot goes, whether structural members are involved, how accessible the damage is, and whether the water source needs correcting — flashing, gutters, grading or drainage. That's why we won't quote rot repair sight unseen. Anyone who does is guessing, and guessing here usually means change orders later.

How to Slow Rot Down (You Can't Stop It, But You Can Win)

That 31-year war against water is winnable — it just takes maintenance instead of heroics:

• Keep gutters clean and make sure downspouts carry water away from the house.
• Repaint or re-stain exposed wood before the finish fails, not after. Paint is your waterproofing, not decoration.
• Keep caulk fresh at trim joints, window sills and butt joints in siding.
• Trim back vegetation so wood can dry between rains.
• Get soft spots probed and addressed as soon as possible. Rot spreads — a small repair this year beats a structural one in three years.

Frequently Asked Questions

How can I tell if my deck is safe or needs to be replaced?

Probe the posts at the base, the ledger where the deck attaches to the house, and the stair stringers with a screwdriver. If any of those structural pieces are soft, get a professional assessment before hosting the next barbecue. Soft decking boards alone are usually replaceable; soft framing is a safety issue.

Can rotted deck posts be repaired, or do they have to be replaced?

A post with surface rot can sometimes be treated and protected, but a post that's soft through the base has lost its strength and should be replaced. The good news is individual posts can often be swapped out with proper temporary support, without rebuilding the whole deck — as long as the beam above is still solid.

I found rot on my siding — what should I do first?

Figure out where the water is coming from before anything else: a gutter, a flashing gap, sprinkler spray, or siding touching soil. Then have the area opened up to check the sheathing and framing behind it. Painting over rotted siding hides the problem while it keeps spreading.

Does pressure-treated wood rot in western Washington?

Eventually, yes — especially at cut ends, fastener holes and anywhere it stays in constant contact with soil or standing water. Pressure treatment slows rot significantly but doesn't make wood immortal here. Cut ends should be sealed and posts kept out of standing water.

Not Sure If It's Okay? Let's Find Out

If you've got a soft step, a wobbly post or trim that gives under your thumb, the honest answer starts with someone actually probing the wood. Roof4Life has been inspecting and repairing rot on Eastside homes — Kirkland, Bellevue, Redmond, Renton and surrounding areas — since 2012, and we'll tell you straight whether a targeted repair will do it or whether it's time to do it right. Call (425) 207-3500 for a free inspection. No pressure — just a clear answer on what's solid and what isn't.