I have a home in the Northeastern USA (Maine). The frost line is roughly 5 feet.

My home appears to be built using posts and piers. I haven't had a chance to start removing things to get a better view of the foundation.

The "crawl space" is very shallow; maybe 2 feet tall on one side of the home. It is not properly enclosed, except with some plastic and lattice.

The insurance company mentioned that I need to have this enclosed. They suggested bricks. It is also extremely cold during the winter on the floor. The floors are very wavey, which suggests that my foundation has other issues or were constructed poorly.

I am not sure how to tackle enclosing (not encapsulating) the crawlspace. I assume I can use bricks or cinder blocks and build a short wall under my home, but I do not know how deep I need to dig. I assume everything will shift over time and the house will separate from whatever enclosure I install since this is not a traditional footer.

What options do I have available?

  • Will probably want a structural engineer to determine if wavy floor is foundation or bad work. Without digging for footers, would not want solid wall to maybe lift up house.
    – crip659
    Apr 20, 2022 at 21:19
  • 1
    Be sure when you enclose it you keep it ventilated or you will have mold problems.
    – Gil
    Apr 20, 2022 at 21:51

1 Answer 1


You have three problems and there are different ways to solve each. I'll start with the easiest.

  1. Enclose the crawl space. This is a small project and serves a few useful purposes, such as reducing heat loss through the floor, reducing the likelihood of pipes freezing, and keeping rodents and other furry friends from bedding in the insulation under the floor. Enclosing the crawl can be as simple as digging a small trench a few inches wide around the perimeter of the home, installing a channel to receive skirting / siding, and other channel on the bottom of the home for the same. Then fill the gaps between the channels with purpose built skirting or cut corrugated vinyl or metal siding to height and install it.

  2. Extremely cold floors. You likely have little or no insulation under the floor. It will be a challenge to keep any in there while the underside of the home is open to the great outdoors. I would spray an inch of closed-cell foam under the subfloor. This is not a fun job (wear a respirator and a bunny suit) but it's very worth while. That first R-6 of foam will air seal the floor, stiffen it up, and make the floor stay a lot warmer. Air sealing under the floor stops indoor air from getting into the crawl space. That indoor air carries lots of moisture which can then condense on cold surfaces. It also often smells of food, which is an invitation for small furry friends to chew their way into the house. The floor joists are thermal bridges so spraying them too isn't a terrible idea.

  3. The wavy floors. There could be any number of reasons for this but it sounds to me like shoddy construction. Perhaps the distance between the floor joists is too wide for the thickness of the subfloor material, letting the subfloor sag between the joists. Or perhaps some of the pier blocks or footings aren't set below the frost line and have bucked or settled. A visual inspection with a good light and a 4 or 8' level can determine exactly why your floors are wavy. Any prescription depends on having an accurate diagnosis.

  • Would probably want to do three before two, at least find the reason first. Some people think wavy floors add charm.
    – crip659
    Apr 20, 2022 at 23:01
  • @crip659, maybe, depends on the diagnosis. If the floor is 1/2" OSB across 24" OC joists, an easy "fix" is adding 5/8" plywood over the existing subfloor, fastening through to the joists, and putting the flooring back down. But if the framing is buckling, probably best to slide in beams, raise the house, install an adequate foundation with perimeter walls, and then set the house onto it, solving 1, 2, &3 in one whack. Apr 20, 2022 at 23:46
  • If you enclose the crawl you either need ventilation or to treat it like part of the conditioned space. Apr 21, 2022 at 22:53
  • Search, "building science sealed crawl." There are alternatives. Apr 22, 2022 at 7:24

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