Pile of cupped flood boards imagery

What Causes Cupped Floor Boards?

What is “cupping”? Not to be mistaken with a newer therapeutic trend, “cupping” floorboards are usually the first obvious sign that a floor is being affected by moisture. Any hardwood floors will naturally expand when exposed to moisture. When only one side of a plank is exposed, that single side will expand. This causes the whole board to warp away from the damp side. Consequently, the plank edges can curl up resulting in an overall wavy appearance.


These problems can arise from seasonal changes, like the summertime when humidity levels rise. In these instances, the expansion tends to naturally correct itself when the seasons change and humidity falls.

One of the most common causes is wet mopping. This should not be done on any hardwood floorboards, especially when the relative humidity in the home is not kept within a 20% range. Cupping can also occur due to faulty plumbing, bad ventilation, and a variety of other circumstances all having to do with excessive moisture in the home.

How do I treat cupping?

In some cases, a cupped floor can straighten out naturally over time on its own. The key here is first determining all potential sources of moisture and acting quickly to treat them before the floor becomes permanently damaged. Until this occurs, a cupped floor cannot become repaired. Once you have located and eliminated any trouble spots, verify that the underlying subfloor is dry by taking readings with a moisture reader.


This may take weeks, months, or even an entire heating season. It is a good idea to take moisture readings at different levels in the flooring. If there’s a difference of 1 percent or more between the top and bottom of the boards, they’re probably not done drying.

If your flooring does not return to an acceptable state, your home most likely has an underlying moisture issue. This problem requires closer inspection by waterproofing professionals like Barrier Waterproofing Systems. We help to determine if the moisture intrusion is coming from the foundation of the home or a crawlspace located beneath the subfloor. Either one is most likely not properly sealed off from the rest of the home.


So just to recap, cupped floor boards are caused by moisture that is intruding into your flood boards. To prevent this problem, you can contact your local waterproofing contractors, like Barrier Waterproofing Systems, and have your floors evaluated for any potential problems. Give us a call at (615) 257-1060 | (931) 536-1168 today!

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