Dry rot is one of the most common and misunderstood problems in Pacific Northwest homes. Despite the name, it does not start with dry wood. This guide explains what actually causes wood decay, where it hides, how to spot it early and what to do about it.
The name is misleading
Dry rot is a common term for wood decay caused by fungi. Those fungi need moisture to start and grow, so wood that is repeatedly or continuously damp is at risk. The name comes from the way badly decayed wood can look dry, brittle and crumbly after the fungus has done its work. The practical lesson is the same either way: if wood keeps getting wet, it will eventually decay, and the cure is to stop the water.
What causes it in Oregon homes
Our climate supplies moisture for much of the year, and certain building conditions make it worse. Clogged or leaking gutters spill water onto fascia and siding. Failed caulk and flashing around windows, doors and trim let water behind the surface. Decks and railings hold moisture where boards meet framing. Soil and plants against siding keep walls damp, and poor drainage sends water toward the foundation. Paint that has peeled leaves bare wood exposed to rain.
Where to look
Check the places water collects: window sills and trim, the bottom of door frames, fascia and rake boards under the roof edge, siding near the ground, deck ledgers and post bases, railings, and fence posts. Inside the home, look for stains, bubbling paint or musty smells near windows and below roof edges. A hidden leak can damage wood for a long time before any sign shows on the surface.
How to test for rot
Press a screwdriver or awl into the wood. Sound wood resists; decayed wood feels soft, spongy or crumbles. Look for wood that is discolored, cracked in a cube-like pattern or sinks under pressure. Paint that peels in the same spot repeatedly is another clue that moisture is working behind it. If you find soft areas, the decay may be larger than what you can see on the surface.
Why it spreads if ignored
Decay does not repair itself, and the moisture that caused it usually keeps coming. A soft piece of trim can lead to rotted siding, and water that reaches framing or sheathing makes the repair larger and more expensive. Finding and fixing the source, whether a gutter, a flashing detail or a missing caulk line, is just as important as replacing the damaged wood. If you only replace the wood, the problem tends to return.
How rot is repaired properly
A proper repair removes all the affected wood, finds and corrects the moisture source, and replaces what was removed with sound material that is sealed, primed and painted. Our dry rot repair service follows that approach for siding, trim, fascia, decks and framing. For broader fixes, see exterior home repairs, and for water management consider our gutter services.
Preventing rot in the first place
Keep gutters clean and working, as covered in our guide to how often to clean gutters in Oregon. Repaint before paint fails, as explained in how often to repaint your exterior. Maintain caulk around windows, doors and trim, keep plants and soil away from siding, and make sure water drains away from the house. A yearly walk-around after the wet season catches most problems while they are small.
Get it checked
If you suspect rot, an inspection will show how far it goes and what caused it. We explain what we find, show you what needs replacing, and give you a written estimate. Request a free estimate or call 503-200-9880.
