Cupping is the bane of many wood floors and something that wood floor owners dread. Cupping occurs because hardwood is a natural material that responds to heat and moisture. Porous woods absorb water over time, which causes them to expand. Heat can also cause them to expand. That’s why particularly humid environments are especially dangerous for a wood floor.
What Causes It?
Cupping is caused when wood planks expand due to heat and/or moisture. That causes the planks to push up against each other. Much like the formation of mountains and valleys, the two pieces pushing against each other causes the edges to rise upward and the middle of each plank to sink. That is cupping.
The first and most effective method for dealing with it is to prevent it in the first place. To prevent cupping from ever occurring, you need to talk with a professional who installs your flooring. A waterproof subfloor is absolutely essential. If you’re on the first floor or if the climate is particularly humid, that might not be possible. In that case, a dehumidifier can help you prevent cupping. However, if that didn’t happen and you have cupping, you need to take a few steps.
What Can You Do?
A caveat must come first; you should not sand a cupped floor smooth until you are sure that it is dry. The hardwood floor and the subfloor must both be dry. If you sand a cupped floor before it is dry, it can dry and then crown. A crowned floor is one in which the middle of the planks begins to rise. Once a floor has been sanded and then crowns, it might be beyond repair. So, make sure it is dry first. The best way to dry it is by calling a professional. The professional will be able to measure the moisture level and recommend the best solutions. If that’s not possible, you should invest in a dehumidifier. That could take weeks or months to get completely dry. So, you’ll have to be patient.
Once you’re confident that it’s dry, you can rent a sander from a hardware store. You’ll need to sand the wood flat again. It will take off the finish as well; so, you need to be prepared to refinish the hardwood floor. If it’s only a few planks, you can do this in a weekend project. If it’s the entire floor or most of the floor, you might need to call a professional and just plan to be out of the house for a few days.