Wet Hardwood Floor Cupping

When moisture interacts with a hardwood floor the side of the boards closest to the moisture expands.

Wet hardwood floor cupping.

The simplest way to think of wood floor cupping is to imagine the edges of each plank sticking up higher than the centers. When the moisture increases the wood swells and then when it decreases the wood shrinks. 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. Wood is hygroscopic in nature and thereby tends to absorb moisture from its surroundings causing problems in hardwood floors.

As you can see moisture and wood don t go well together. The general effect is easy to demonstrate by putting a small strip of paper onto a small drop of water. 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. It ends up looking a little like an accordion.

The paper will curl up away from the water. This expansion can be in the form of cupping the center of the board is lower than the edges or crowning the center of the board is higher than the edges.