Crawl space repair, the structural half

What is crawl space repair?

Crawl space repair covers two entirely separate categories of work that share a location. This page is about the structural one: the posts and footings holding your floor up, the wood at the bearing points, and the builder-grade supports that were never adequate. The other category - vapour barriers, sealing, humidity control and encapsulation - is a moisture project, covered by crawl space encapsulation. Knowing which one you need is most of the decision.

Signs you need crawl space repair

• A support post standing out of plumb, sitting on bare soil, or with its shims fallen out and lying beside it
• A stack of concrete blocks serving as a support that has cracked, tilted or partly collapsed
• A visible gap between the top of a post and the beam it is supposed to be carrying
• The end of a girder or joist that is dark, soft or crumbling where it enters the foundation wall pocket
• Sill plate along the perimeter that gives way under a probe rather than resisting it
• A floor above that has developed a localised dip or a soft spot over one particular area
• Insulation hanging down, obscuring the framing it was installed to insulate - and hiding the condition of everything behind it
• A crawl space you have never entered, in a house you have owned for years

Seeing something not on this list? Browse foundation repair problems by symptom →

How crawl space repair actually works

1. 1

   Get somebody under there who is not selling a package

   The crawl space is the least-inspected part of most houses and the easiest place to be told anything. An assessment from someone who does not sell either encapsulation or underpinning is worth more here than almost anywhere else in the building.

   Watch forAn inspection that arrives with a fixed product in mind. If the visit ends in the same proposal regardless of what was found under there, you learned about the company rather than the house.

2. 2

   Deal with access and clearance honestly

   Low headroom, standing water, ductwork blocking the route and buried debris all limit what can be reached, and they change what any repair costs. Access is a legitimate line item, not padding.

   Watch forA full assessment claimed for a space with a blocked route or an area nobody could physically reach. Ask directly which parts were inspected and which were not, and get the unreached areas listed.

3. 3

   Examine every support, and what each one stands on

   Each post or column gets checked for plumb, for bearing at the top, and for what is underneath it. Builder-grade supports set on thin footings or directly on soil are extremely common and settle predictably over decades.

   Watch forSupports on inadequate footings replaced with new supports on the same inadequate footings. The post gets renewed, the reason it failed does not, and the failure repeats on a schedule.

4. 4

   Probe the bearing points, not the middle of the members

   Deterioration concentrates where wood meets masonry and where water has run - beam pockets in the foundation wall, sill plates, the base of posts, and the ends of joists at the rim. The middle of a joist can be perfect while the end sitting in the wall is gone.

   Watch forWood assessed visually through a layer of fallen insulation. Insulation has to come away for the framing behind it to be judged, and any report that skipped that has judged the insulation.

5. 5

   Identify the water source before rebuilding

   Rot means sustained moisture, and the structural crew is not usually the one who fixes it. Ground water, a failing drain, condensation on cold surfaces and surface water entering from outside are different problems with different owners. This page hands that half over deliberately.

   Watch forTwo contractors each assuming the other is handling moisture. Name the responsible party in writing, because "we thought they were doing it" is how new timber ends up back in the same conditions.

6. 6

   Replace or reinforce the compromised structure

   Failed supports are replaced onto footings capable of carrying them, deteriorated timber is cut back to sound material, and bearing is properly re-established at each point. Temporary support carries the load while that happens.

   Watch forSistering new material alongside rot without removing the deteriorated wood. It looks like a repair from the access hatch and leaves the decay in place, with the moisture that produced it still available.

7. 7

   Handle mould and air quality as a separate question

   Growth on crawl space framing is a moisture consequence and an indoor-air question, and it is a specialist trade with its own protocols. Start at the mould remediation services index rather than treating it as part of the carpentry.

   Watch forSurface treatment sprayed onto framing and presented as remediation, with nothing done about the humidity keeping it alive. That is a cosmetic result on a structural surface.

8. 8

   Document the work and leave the space usable

   You want photographs of each repaired location, a note of what was replaced and what was left, and the space left with access maintained rather than sealed off behind whatever was installed last.

   Watch forA vapour barrier laid over new structural work with no photographic record underneath it. The next person who needs to check that repair will be lifting up something you paid for.

What does crawl space repair cost?

Structural crawl space work ranges from replacing a handful of supports onto proper footings, at the low end, to substantial figures once girder ends, sill plates or joist ends need cutting back and replacing. Restricted access and standing water raise every line on the quote.

See the full crawl space repair cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →