Crawl Space Structural Repair in Tacoma, WA
Sistered joists, replaced sills, and new posts and piers under a house whose framing has been standing in wet crawl space air for decades.
What Fails Under a Wet Tacoma House
Crawl space repair replaces or reinforces framing that moisture has damaged: sistering joists, replacing rotted sills and rim boards, and setting new posts and piers under sagging beams. In Tacoma a new post on a footing runs about $800 to $2,500 and a sistered joist about $150 to $350.
Wood in a Tacoma crawl space spends five months a year at a moisture level where fungi grow. Douglas fir framing tolerates a great deal, but a post standing in seasonal water, a sill on a damp stem wall, or a joist under a leaking bathroom eventually goes soft. Sixty-four percent of Tacoma's housing predates 1980 and 43 percent predates 1960, so a large share of the crawl spaces here have had sixty to a hundred wet winters to work on the framing.
Posts and piers
The most common Tacoma failure. Older houses were built with wood posts on concrete pier blocks set on the soil, or on no footing at all, and the post bottoms wick water from the ground every winter. They rot from the base up, the beam above drops, and the floor sags toward the middle of the house. Sometimes the pier has sunk or tilted in the soft ground instead. The repair is a new pressure-treated or steel post on a poured footing, with the beam jacked back toward level first.
Sills and rim joists
The sill plate sits on the stem wall, and on pre-1970 houses it is usually untreated lumber with no gasket, in contact with damp concrete. Rim joists rot where foundation vents let rain blow in or where the grade outside is above the sill. Replacement means supporting the floor, cutting out the rotted length, and sistering or replacing it in sections.
Joists, beams, and subfloor
Joists rot at the ends where they bear on a wet sill, and under bathrooms and kitchens where plumbing has leaked. Beams fail at the post connections. Subfloor delaminates where it has been damp from below for years, which shows upstairs as soft or cupped flooring. A joist is sistered with a full-length partner bolted alongside; a beam is replaced or reinforced with a steel flitch plate or an added post; subfloor is cut out and replaced from below or above.
What It Costs in Tacoma
- Sistered joist: about $150 to $350 each, more when plumbing or ducts are in the way.
- New post and footing: about $800 to $2,500 per post, including jacking the beam.
- Sill or rim joist replacement: about $100 to $200 per linear foot, done in sections.
- Beam replacement or reinforcement: about $5,000 to $18,000 depending on span and access.
- Subfloor replacement: priced by area; a bathroom floor from below is roughly a day's work.
- Access and cleanup: low clearance adds to every line above, and rodent or mold contamination is cleaned before a crew works in it.
A house with two or three rotted posts and one bad sill section is roughly a $3,000 to $8,000 job. A house whose beam has been resting on the ground for years is more. Neither number means much until someone has been under the house with a moisture meter and a probe. The cost guide puts these beside the other crawl space work.
Permits, Sequence, and What to Ask
Tacoma's permit exemptions cover ordinary repairs but not the removal or cutting of any structural beam or load-bearing support, so post, beam, and sill work usually involves Planning and Development Services, and a contractor should say so in the bid. Outside city limits the county's Planning and Public Works handles it.
Structural repair comes after the water is stopped and before the liner goes down, because the crew needs bare ground and open access, and because a new post standing in the same seasonal water as the old one has the same life expectancy. A contractor who quotes encapsulation without a word about the posts and sills has either found them sound or has not looked; ask which.