Crawl space repair cost

Repairing a crawl space costs $3 to $15 a square foot, typically around $7, so a 1,200 square foot crawl space is $3,600 to $18,000. That range is wide because it covers two different kinds of work: sealing the space against moisture, and repairing wood that moisture has already damaged.

Only the second of those is repair in the strict sense, and it is the half that decides the price. Sealing a dry crawl space is a predictable job priced by the square foot, covered in Crawl space encapsulation cost at $3 to $10 a foot. Replacing a girder that has been wet for fifteen years is not predictable, and this article is mostly about that.

A crawl space is the part of a house nobody looks at, which is why problems there run for a decade before anyone notices, and why the noticing usually happens because the floor above has started to sag.

What it costs

Job	Typical cost
Crawl space inspection	$200 to $500
Structural engineer's report	$400 to $1,200
Removing debris and old insulation	$500 to $2,500
Mould remediation	$1,500 to $6,000
Sistering a joist	$150 to $500 each
Replacing a joist	$250 to $800 each
Rotted sill plate, per linear foot	$60 to $200
Girder or beam repair	$1,000 to $5,000
New support pier or jack post	$300 to $1,200 each
Levelling a sagging floor	$2,000 to $10,000
Perimeter drain, per linear foot	$30 to $90
Sump pump and pit in a crawl space	$1,000 to $3,500
Crawl space dehumidifier	$1,200 to $3,500
Pest exclusion and screening	$300 to $1,500
Encapsulation, priced separately	$3 to $10 per sq ft

Most crawl space quotes are a bundle of several of these lines. Ask for them itemised. A single per-square-foot number hides whether you are buying structural repair, moisture control, or a plastic sheet.

Find out what is wrong before you price the fix

The order matters here more than in most home repairs, because the companies that inspect crawl spaces mostly also sell crawl space work.

Pay $200 to $500 for an inspection, or go yourself with a torch, a mask and old clothes. If anything structural turns up, spend the $400 to $1,200 on an independent structural engineer before you take repair quotes. Structural engineer cost covers what that buys you. The reason is the same as with any foundation work: the person diagnosing should not be the person selling the fix, and an engineer's scope turns three wildly different quotes into three prices for the same job.

What you are looking for, in rough order of seriousness:

A floor above that slopes, bounces, or has developed a hump along one line
Doors and windows on the ground floor that have started to stick
Wood that gives when you push a screwdriver into it, particularly at the ends of joists and where the sill sits on the foundation
Piers that have tilted, settled, or are wooden posts standing on bare soil
Standing water, or a tide line on the piers showing where water has stood
Sagging, darkened insulation, and mould on the underside of the subfloor
Mud tubes on the piers or walls, which mean termites

Damp insulation — Wet insulation hanging out of the joists is the visible half of the problem. What decides the bill is the wood above it, and how long it has been wet.

The structural findings

Rotted joist ends. The commonest finding, and the cheapest to fix while it is still only the ends. A joist is sistered by bolting a new member alongside the old one for its full bearing length, at $150 to $500 each. Where the rot has run further in, the joist is replaced instead at $250 to $800. Crews price these per joist, so the total depends entirely on how many, which is why the engineer's report is worth having before the quote.

A rotted sill plate. The sill is the timber lying flat on top of the foundation wall, carrying everything above it. When it goes, the fix is $60 to $200 a linear foot, and it means temporarily jacking and supporting the wall above while the timber is cut out and replaced. It is slow, skilled work and the price reflects that.

Settled or inadequate piers. Interior piers carry the girder that carries the floor. Older houses often have piers that were undersized to begin with, built on no footing, or replaced at some point with a wooden post standing on soil, which in a damp crawl space is a post with a service life. A new pier or adjustable jack post on a proper footing is $300 to $1,200 each.

Girder and beam damage. The girder is the main horizontal member the joists land on, so a failure here shows up across a whole room rather than one board. $1,000 to $5,000 depending on span and access.

A sagging floor. Levelling is $2,000 to $10,000, and it is done by degrees, usually a quarter turn on the jack posts every week or two over a month or more. A crew that levels a floor in one afternoon will crack the drywall, the tile and sometimes the windows upstairs. If a quote promises it in a day, that is the thing to ask about.

Termite or beetle damage. Found in crawl spaces more than anywhere else, because they are dark, damp and unvisited. The insects are a separate treatment from the carpentry, and both are needed.

Do it in this order

Water first, then wood, then air. Fix what is letting water in with grading, gutters, a perimeter drain or a sump. Then repair or replace the damaged framing and treat any mould. Encapsulate last, once the space is dry and sound.

Running that order backwards is the expensive mistake, and it is common because encapsulation is the part that gets sold. A sealed liner laid over a wet crawl space traps the water under it, hides the rot from the next person who looks, and has to come up again when the joists are finally dealt with. You pay for it twice.

What waiting costs

Crawl space damage compounds in a way that most home repairs do not, because the cause stays present. A joist end with early rot is a $300 fix. The same joist three years later is an $800 replacement. When enough of them go, the girder follows, and the girder is what turns a four-figure job into a five-figure one.

There is a resale dimension as well. Structural findings in a crawl space are disclosable in most states, they show up in any competent buyer's inspection, and buyers discount them well beyond the cost of the repair. Selling a house with foundation problems covers how that plays out.

Frequently asked questions

How do I know whether it is structural or just damp?

Damp is what you smell and see. Structural is what you feel upstairs. Sloping or bouncing floors, doors that have started to stick, and cracks over doorways on the ground floor are the signs that the problem has reached the frame. If the crawl space is wet but nothing upstairs has moved, you likely have a moisture job rather than a repair.

Does homeowners insurance cover it?

Rot, mould and long-term moisture damage are excluded on standard policies as maintenance. A sudden event, such as a burst pipe, is generally covered, and the resulting damage with it. The distinction insurers draw is sudden against gradual, and crawl space damage is nearly always gradual.

Can I repair joists myself?

Sistering a joist is achievable if you can get to it, and many people do. Anything that carries load while you work on it is not: sill plates, girders and piers all mean supporting the house temporarily, and getting that wrong in a three foot space is dangerous rather than merely expensive.

How long does the work take?

A few days for joist repairs and remediation. A week or more where a sill plate or a girder is involved. Floor levelling runs over a month because it has to be done gradually.

Should I fix it before selling?

Usually yes for structural findings, because buyers discount for uncertainty and their number is worse than your quote. Get the engineer's report and the repair invoices, and hand both over. A documented repair is worth considerably more at the table than a disclosed defect.