Wood Rot Behind Siding and Trim Repair in Vancouver, WA

Because the wall rarely gets a chance to dry. Dry rot is a wood-eating fungus and it gets going when wood stays above roughly 20 percent moisture content for long enough, which from about October through May around here is not a high bar to clear. The monthly rainfall normals for the Vancouver 4 NNE station say the same thing in inches: December averages 6.79, November 6.31 and January 6.05, with 14.8, 13.5 and 13.3 days of at least a tenth of an inch. July averages 0.48 inches over 1.4 days.

So the wood behind your siding has eight months of water and four months to recover. One Camas and Vancouver installer puts it at close to a coin flip: roughly half the houses it re-sides have dry rot somewhere, and most of it is small. That is the useful part. Half the time the answer is a few boards, not a wall.

Trim, fascia and exterior molding go first, and they are also the cheapest to put right. On the 2026 ranges published for Portland and Vancouver, WA, a small trim or fascia section runs $300 to $1,200, a window frame or sill $400 to $1,500 and an exterior door jamb $400 to $1,000. Past the trim the figures step up: one area of siding including replacement is $1,000 to $5,000 on the same page, a roof rafter or sheathing repair $1,500 to $10,000, and a major structural rot project $8,000 to $25,000 plus.

The ordering is about access and load rather than material cost. Trim, fascia and exterior molding are cheapest, window frames, door jambs and decking sit in the middle, and rafters, structural beams and ledger boards are the most expensive. A second local page prices the minor end of the work, rotted trim, a corner board or a few courses with no sheathing damage, at $350 to $1,200. Full numbers for new cladding are on the Vancouver, WA siding cost guide, full siding replacement covers the other way out, and how we price siding explains where every range came from.

Most often a missing kickout flashing. Where a roof edge dies into a wall there is supposed to be a small diverter that kicks water out into the gutter, and on a lot of older Clark County homes it was never installed, so every rainstorm sends water straight down inside the wall. One local installer calls it the single most common cause of serious rot it finds.

The rest of the list is short and it is worth walking your own house against it:

• Original siding from the late 1970s through the mid-1990s. Hardboard and T1-11 soak up water at every cut edge.
• Gutters that overflow. Years of water sheeting down one wall does exactly what you would expect.
• Siding buried in the dirt. It should stop several inches above grade, and landscaping built up against the house wicks moisture year-round.
• North-facing walls. They never get enough sun to dry out.
• Anything punched through the wall. Deck ledgers, hose bibs and dryer vents are all places water gets in.

Which wall you are looking at matters too. Age is the single biggest swing in a siding quote: pre-1980 homes in Minnehaha and Hazel Dell turn up this kind of damage regularly, while a newer subdivision house in Ridgefield usually has one installation defect instead.

You find some of it from the outside and you accept that the sheathing is invisible until it is not. Six things worth a walk around the house, from a Clark County installer's own list:

• Paint bubbling or peeling in one specific spot rather than all over.
• Trim that feels soft or spongy when you press a thumb into it, especially at the bottom of corner boards.
• Dark staining running downward from a window corner or a roof-to-wall junction.
• Siding that has swelled or delaminated along a cut edge.
• An interior clue: a stain on the drywall at a window corner, or a cupped baseboard.
• A musty smell in a closet on an exterior wall.

Then there is the screwdriver test. Push a screwdriver into a suspect spot with moderate pressure: sound wood pushes back, and rotted wood takes it like styrofoam. A contractor doing this properly probes with an awl until it hits dense wood, because by the time rot is visible it has usually been working on the wood for a year or longer. What you can reach yourself is trim and siding, and the structural wood behind that is a separate question. Vancouver Prime Siding doesn't inspect walls or test wood; how we vet our siding pros explains what we do check.

The price changes, and the honest version of that is written into the bid before anyone starts. One local installer quotes siding as a firm number and bills rot as time and material, on the reasoning that any contractor handing you a fixed rot price before the siding is off is either padding the bid with an allowance big enough to cover the worst case or planning a change order later. Pay for the first and you overpay when the house turns out to be fine.

That installer's sequence is a fair template for what your written scope should promise:

1. Work stops when rot is found, and nothing is repaired before you know about it.
2. It is photographed and the pictures are sent the same day.
3. You get an estimate of hours and material for that specific area.
4. You say go before anyone goes.
5. Material receipts and tracked hours are yours to see.

Ask for a rot-repair rate in the bid rather than a rot allowance, and ask what a moderate find does to the schedule. A moderate repair usually adds a day or two, and a major structural one can add a week. The hiring checklist covers the rest of what belongs on paper, and estimates for the same rot job often vary by 30 to 60 percent, which is almost always scope rather than pricing.

Cutting well past where the rot stops, treating what is left, and fixing the water. One installer goes at least a foot beyond where the rot stops; another's rule of thumb is to extend the cut at least 18 inches past the last point of probe penetration, because fungus travels farther than it shows. Cut edges and adjacent sound wood get a borate preservative, which stays active for decades and is invisible once paint goes on, and that is part of why cheap repairs skip it. Replacement trim and siding go back in matching material, primed on all six sides before install.

Then the cause: new kickout flashing, head flashing over the window, a gutter that drains, siding held up off the grade. Skip that and you pay for the repair twice. Rebuilding means a new weather-resistive barrier with the flashing lapped in the right order before the cladding goes back on. Epoxy filler has a place on a small non-structural spot, such as a trim board or an otherwise solid sill, but not on anything holding weight or anything that reaches the sheathing. Painting over rot is worse: paint seals the moisture in, the wall looks fine for two years, and then the repair triples. There is more on failed patches on the siding repair page, and repair or replace covers the point where patching stops paying.