The simplest way to think of wood floor cupping is to imagine the edges of each plank sticking up higher than the centers.
Wet hardwood floor cupping.
Underlayment and or subfloor that is too wet at the time of installation will cause wood floor cupping.
The general effect is easy to demonstrate by putting a small strip of paper onto a small drop of water.
The paper will curl up away from the water.
Wood is hygroscopic in nature and thereby tends to absorb moisture from its surroundings causing problems in hardwood floors.
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.
As you can see moisture and wood don t go well together.
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.
When moisture interacts with a hardwood floor the side of the boards closest to the moisture expands.
Cupping is a result of the changes in moisture in the room.