Wet Hardwood Floor Cupping

It ends up looking a little like an accordion.

Wet hardwood floor cupping.

The general effect is easy to demonstrate by putting a small strip of paper onto a small drop of water. As you can see moisture and wood don t go well together. A cupped floor develops as moisture from the underlayment or subfloor moves upward through the hardwood as the back of the wood becomes wetter than the face of the wood. The simplest way to think of wood floor cupping is to imagine the edges of each plank sticking up higher than the centers.

Wood is hygroscopic in nature and thereby tends to absorb moisture from its surroundings causing problems in hardwood floors. Cupping in solid wood floors cupping occurs in solid wood flooring as a result of an elevated mc in the bottom of the flooring compared with the mc of the face. Cupping is a result of the changes in moisture in the room. If you imagine a picture of a child drawing a boat in the water then the water will give you a good idea of what a cupped floor looks like.

When moisture interacts with a hardwood floor the side of the boards closest to the moisture expands. The paper will curl up away from the water.