Knowledge Center

Cupping Hardwood Floors - What to Do?

October 26, 2015

One of the biggest problems anyone with hardwood floors will ever face is a phenomenon known as "cupping". What is cupping and what can be done about it? Here are some answers.

What is Cupping?

Cupping occurs whenever the individual planks of a floor become concave in the center and rounded on the sides, thereby creating a sort of “cup” or bowl. This problem can happen with either solid or engineered hardwood flooring, and is a response to changes in the moisture content of the wood. Water vapors from a subfloor can also cause cupping to occur, as can being exposed to excess amounts of water such as during flooding.

Associated Problems

Minor cases of cupping are often resolved whenever the moisture content of the wood returns to normal again. However, in many instances, the plank becomes “set”, and does not return to its original size and shape. When this happens, the plank is said to be “compression set.” Wood flooring that has become compression set may eventually develop permanent gaps between the boards that could result in drafts, excessive creaking, and an unsightly appearance overall.

Remedies for Minor Cupping

When cupping is only minor, it can often be eliminated by simply removing the source of water and then thoroughly drying out the floor. It’s important to note that getting rid of cupping in this manner is a rather lengthy process, as gradual changes may occur over a period of weeks or even months. Running a fan or dehumidifier in the room where cupping has occurred will sometimes speed up the process. It’s important to protect the floor from further water damage during this drying-out period as well.

Resolving Serious Cupping

Repairing floors with severe cupping requires a great deal more time and effort. In many cases, individuals may have to completely remove everything from the room to allow for better airflow. Removing baseboards could also be needed, especially if sanding is recommended. Sanding the floors with a floor sander using 36-grit sandpaper can often level out floors that are severely cupped. A special hand-held floor sander could be needed in order to reach planks that have deeper cups. If floor sanding fails to resolve the problem, the only other alternative may be to replace certain planks.

Preventing Cupping

There are several things individuals can do to prevent their floors from cupping in the first place. One of the biggest ways is to keep indoor air at an even temperature all year round. Homeowners should also be aware of any hidden sources of moisture so they can take steps to eliminate it if possible. Using a dehumidifier might also be recommended in areas where hot, humid temperatures are the norm during the summer months.

The best way to prevent hardwood floors from cupping is to make sure they are professionally installed. Floors should also be inspected on a regular basis for signs of cupping so that the appropriate measures can be taken to contain it early on.