Deck Rot and Structural Repair in Seattle

Between $800 and $3,000 for most framing jobs, going by the tiers Seattle companies publish, and more once several members are gone. Four local firms price the same work differently, which tells you how to ask for it:

• A Seattle remodeler: $800–$1,600 for ledger board and support post replacements, and $2,000–$3,000 once the job includes beam and joist replacements
• A Seattle deck company, priced per part: $200–$400 per sistered joist, $400–$900 per post on an elevated deck including the temporary shoring, and $1,500–$4,000 for a ledger replacement
• A Seattle and Bellevue builder: $1,500–$6,000 for structural repair to joists, beams or the ledger, and past $10,000 for a major structural rebuild
• Boards only, if the frame turns out to be sound: $300–$1,500 to replace a few rotted or cracked ones

Per-part pricing is the one to ask for, because rot is almost never spread evenly. Two soft joists and one post base is a different invoice from a beam. New-build pricing sits in the deck cost guide, and re-decking a frame that is still good is covered under deck repair and replacement.

Because the wood never gets a chance to dry. A Seattle repair contractor puts it plainly: wood does not rot because it gets wet; it rots because it cannot dry out. North-facing sections, the seam where two boards meet and any corner where leaves pile up stay damp for months at a stretch, and that is where it starts.

The damage also runs ahead of the evidence. End grain on joists, posts and ledger boards soaks up moisture fastest, so rot works from the inside out, and a Seattle deck company reckons that by the time surface deterioration shows, the structural problem is typically six to twelve months old. Another local builder says the same thing from the other side: visible rot on the surface usually means it is already in the joists underneath.

Seattle's code pushes back on one part of this. You must use treated wood, or wood that naturally resists decay, for any wood that will touch concrete close to earth. That rule protects post bases. It does nothing for a ledger with bad flashing, which is why cedar and pressure-treated decks on a shaded lot need closer watching than ones out in the sun.

In Bellevue and Edmonds, yes, and it catches people out because nothing is being added. Each city words the trigger differently:

• Bellevue. No permit for installing or repairing a deck less than 30 inches above the ground. Above that, a permit with plan review is required for installing, repairing, replacing and adding to decks where the highest walking surface is more than 30 inches up, and separately for repairs to existing deck or porch handrails and stairs. The city's single-family addition permit lists the repair or replacement of existing deck structural framing as covered work. See Bellevue.
• Edmonds. A permit is required for the construction, repair, replacement, relocation, enlargement or alteration of decks, with a narrow exemption for an uncovered deck no more than 30 inches above grade. See Edmonds.
• Renton. Repair and replace both appear in the city's general trigger: a permit is required to construct, enlarge, alter, repair, move, demolish, convert, replace or install a building structure. See Renton.
• Seattle. The city's deck list goes by height, location and size rather than naming repairs, so a raised deck is in scope and a low one may not be. The Seattle permit guide has the thresholds.

A Seattle repair contractor's rule of thumb matches that: swapping like-for-like boards or a section of railing generally needs no permit, while structural work, meaning joists, beams, the ledger or rebuilding a raised deck, often does. All seven cities are set side by side on deck permits across the Seattle-area towns, including Redmond.

By probing, not by looking. The test a local contractor describes is to poke suspect wood with a screwdriver: if the blade sinks in, or the wood is dark and crumbly, that is rot rather than weathering. One Seattle firm charges from $150 for a site evaluation and deck condition assessment and from $180 for a moisture inspection and report, which is cheap against the repair it prices.

Ask for these five to be probed:

• The ledger where the deck meets the house, and the flashing above it. When that flashing fails, the rim joist inside the wall rots over three to five years, and that is house framing rather than deck framing
• The ends of the joists, where they sit on the beam or in the hangers
• Post bases, and the footings under them
• The beam at its connection points
• Stair stringers, and the treads at their outer ends

Get the findings in writing, member by member, before you agree a price. How we vet our deck pros covers the registration check we run before a pro joins, and the hiring checklist covers the one you can run yourself in about a minute.

Once it turns up in several places at once. A Seattle deck company's position is that rot in multiple posts, joist ends or the main beam leaves you a structural rebuild rather than a repair, and priced properly that rebuild routinely comes in at 60 to 80 percent of a full replacement. At that ratio you are paying most of a new deck's price for an old deck's remaining life.

Both paths, and the point where one overtakes the other, are priced on repair or replace your Seattle deck. If water is running through the deck into a room below rather than into the frame, start with leaking decks and waterproofing instead. Either way, send the details and our vetted local deck pro arranges a look.