Crawl Space Repair in Ann Arbor

Old crawl spaces are often held up by whatever was handy: dry-stacked block on bare dirt, wood posts sitting on soil, a pile of shims. Over time the block sinks, the posts rot and the girder above sags between them. Steel support jacks replace those piers. Each one is a steel post with a threaded head, set on a concrete footing pad on firm soil, and turned up in small steps until the girder is back to its line.

Where the girder itself is too far gone, it gets replaced as well, and the clearance rules matter here. In a crawl space, a girder closer than 12 inches to the soil, or joists closer than 18 inches, has to be pressure-treated or naturally durable wood. In a low crawl, that means the new beam is treated lumber. Column sizes and the code's minimum for steel posts are on the sagging floor repair page.

The sill plate is the board bolted flat on top of the foundation wall, with the rim joist and the house's walls sitting on it. It rots where water reaches it: soil and mulch piled against the siding, gutters that spill at the corner, a leaking hose bib. Michigan's code requires treated wood for framing that rests on a foundation wall less than 8 inches above exposed ground, and many older sills were never treated.

The repair takes the weight off the wall first. The crew shores up the floor framing with temporary posts or cribbing, cuts out the rotted run, slides in a pressure-treated sill with new anchor bolts, then sisters or replaces the rim joist. HomeGuide's figure (September 2025) is $120 to $200 per linear foot, or $3,000 to $5,000 for a 25-foot run, and it notes that most cities want a permit for this. Fixing the cause is part of the job: grade pulled back from the siding and water sent away from the wall (the grading rule is on basement leak repair).

Crawl space walls are short, usually a few courses of block or old stone, but they carry the same load as a basement wall. They crack along the mortar joints, lose stones, or lean in where wet clay pushes on them. The repairs match the wall type: repointing and rebuilding courses on block (block foundation repair), lime mortar on stone (stone foundation repair).

Two code details come up when a crawl wall is rebuilt:

• Vents. A vented crawl space needs 1 square foot of opening for every 150 square feet of floor area, or 1 for every 1,500 where the ground is covered with a Class I vapor retarder. An unvented crawl instead needs a continuous vapor retarder lapped 6 inches at the joints and run at least 6 inches up the wall.
• Access. The crawl must stay reachable: at least 18 by 24 inches through the floor, or 16 by 24 inches through a perimeter wall.

Vapor barriers and full encapsulation are a separate trade's work. Our view: do them after the walls and supports are fixed, not before, or the new plastic gets torn up.

A common pattern: a house with a full basement and a family room or porch added later on a shallow crawl. If the addition's footings don't reach frost depth (the Michigan rule is on helical piers for decks and additions), it moves with the seasons while the main house stays put. The signs are a crack where the two meet, a floor that steps down at the doorway, and a roof joint that keeps leaking.

The fix is usually to stop the addition settling with piers under its footing, driven from outside or through the crawl, and then lift it back toward the main house. Helical piers covers the pier types. Access is the hard part: some of these crawls have barely two feet of clearance, and the crew may need to cut an access opening.