The floors in your home should be firm and even. They shouldn’t bulge downward underfoot. Neither should there be visible gaps between your floors and baseboard trim. Neither should a marble be pulled by the momentum of a sharp decline. These examples are signs of uneven floors, and here are four causes.

Compromised Soil Beneath a Slab Floor

Many homes have basements or crawl spaces, while others have concrete slab floors with no structural wood flooring system. Uneven floors in homes with slab floors are almost always the result of soft soil or bad soil compaction.

When soil becomes compromised a slab can shift and create a sagging or sinking effect. Sometimes pressure from a shift can cause the slab to crack, and create high and low points on your flooring.

Water Intrusion, Humidity, and Insects in Crawl Spaces

Homes with crawl spaces typically have a mostly wood framing support structure that sits on top of the foundation and supports the subfloor above, and thus the structure is prone to damage from water intrusion, humidity, and insects.

Water Intrusion

If water collects in your crawl space, your home’s structural wood framing system—which includes the sill plate, wood beams, and floor joists—becomes susceptible to rotting. (The sill plate connects the house to the foundation).

When water saturates these wood components it leads to deterioration, which ultimately causes your subfloor above to fail.


High humidity in your crawl space can also damage the beams and joists that support your subfloor. Because wood is very porous it easily absorbs moisture from the air. Over time, water saturation softens and rots these structural components. As they decay they compress under the weight of your home, and can lower the height of your floors sometimes by several inches.


Bugs like termites, and even certain beetles, can be enemies of your floor’s structural wood. Many subspecies of beetles eat wood, including the Powderpost beetle—which can be difficult to identify because an average adult beetle is smaller than a grain of rice. These beetles lay their eggs inside of wooden beams, and when the larvae hatch they eat the wood. Beetles and termites will infest and damage your structural wood flooring system.