From the older streets of Sikeston to the bluffs of Cape Girardeau, most houses built before the 1980s sit on a crawl space: a short gap between the ground and a wood floor system, with vents in the foundation wall. Newer construction here is mostly slab, and flooring over a concrete slab covers that side. The two behave completely differently under a floor, and the crawl space is the one that catches people out.
This is what a crawl space does to a floor in this climate, which floors handle it, which ones fail, and the one check we do before recommending anything.
What a crawl space does to a floor
The Bootheel is flat alluvial ground with a high water table, and it gets around 48 inches of rain a year in a humid climate. Under a house, that means the soil in the crawl space is releasing moisture constantly. Some of it leaves through the vents. The rest rises through the wood subfloor and into whatever floor is on top.
A floor over a crawl space is therefore being loaded with humidity from below while the air conditioning dries it from above. Products that absorb moisture, solid wood and to a lesser degree laminate, expand and contract with that imbalance. That is what cupping is, and it is why a hardwood floor in a Bootheel crawl-space house so often looks wavy by the end of its first summer. We do not install hardwood at all, and the crawl space is a large part of why we are comfortable saying that in this part of the state.
In older houses the subfloor itself has taken decades of this, and boards near exterior walls and under bathrooms are often soft. The subfloor decides the job covers what we do about that once the old floor is up.
The check that matters
Before we recommend a product, we put a moisture meter on the subfloor in every room. The reading tells us two things: whether the floor is dry enough to install over today, and whether the crawl space is a problem that will shorten the life of whatever we put down.
If the readings are fine, the choice is about the room. If they are high, we tell you, and we tell you what to do about it: a plastic vapor barrier laid over the crawl-space soil, which is cheap and does most of the work; working vents, or a dehumidifier in a sealed crawl space; and fixing any plumbing leak or downspout that is dumping water against the foundation. Those are not flooring jobs, so we do not do them, but we will not install a floor on top of a wet crawl space and pretend it will be fine.
Which floors handle a crawl space
Luxury vinyl plank: the default. LVP is not wood-based, so the humidity coming up through the subfloor does not swell it. It floats, so it can move fractionally with the seasons without being held tight to a subfloor that is moving too. And it is waterproof from above, which is a separate benefit in a kitchen or bath. Over a crawl space we favor a rigid-core plank with an attached underlayment. It bridges the slight unevenness of an old wood subfloor and it puts a layer between the plank and the boards.
Carpet: the right answer in bedrooms. Carpet over a crawl space is noticeably warmer in winter than any hard surface, because the pad insulates the room from the cold air below, and carpet breathes, so humidity from the subfloor passes through rather than being trapped. It is what most bedrooms in these houses have and should keep. A good pad matters more here than over a slab.
Laminate: fine in dry rooms, with one condition. Laminate has a wood-based core, so it responds to the humidity from below more than vinyl does. It works well in a living room, hallway or bedroom over a crawl space provided it sits in the house for several days before installation, so the boards reach the moisture content of the room rather than the truck, and provided the expansion gap at the walls is respected. Keep it out of the kitchen, bath and laundry over a crawl space, where water from above and humidity from below meet. LVP or laminate in a Bootheel home covers the split.
Tile: possible, with the right base. Tile over a wood floor system needs a stiff enough floor and a cement backer board or uncoupling membrane, or it cracks along the joists. In a small bathroom over a crawl space it is a good, permanent answer if the floor is stiff. Across a large room over old joists it usually is not worth the prep.
Which floors fail
Solid hardwood, for the reasons above, and we do not install it. Glue-down plank over a subfloor that reads high, because the adhesive bond is fighting moisture from below. Any floating floor installed with no expansion gap, or pinned under a cabinet, over a subfloor that moves seasonally. And anything installed over a soft, damp subfloor that should have been repaired first.
The cold-floor problem
Crawl-space houses are cold underfoot in January, and a new hard-surface floor makes that more noticeable than the carpet it replaced. There is no complete fix short of insulating the crawl space, but two things help: choosing a plank with a thicker attached underlayment, which adds a little insulation, and keeping carpet in the rooms where you stand barefoot. It is worth thinking about before running vinyl through a bedroom.
What we do on the visit
We come to the house with samples, measure, meter the subfloor in every room, and look under a corner of the existing floor. If the crawl space is a problem we say so and explain what will fix it. Then you get a written figure with the flooring, removal, any subfloor repair and the transitions as separate lines. Most of the crawl-space houses we work in are in Sikeston, Scott City, New Madrid and the older parts of Cape, and we are in all of them every week.
The estimate is free. Book one here or call 573-471-8700.
