Wood Floor Cupping: A Primer
Photo: Claude Taylor/Flickr
You may think that installing hardwood flooring is about as do-it-yourself as any home improvement job could be. After all, you only have to get enough material and hit the pieces into place with a rubber hammer, right? Well actually, there are complications that require precision in installation to avoid problems later, and one of the biggest ones is “cupping.”
Cupping is a problem that can occur in all hardwood floors to some degree. If you’ve never heard of it before, maybe your floor has never been affected badly enough to notice it, though trained flooring professionals can spot it. If you have a hardwood floor, here are the basics about cupping.
What is it?
Hardwood boards are cupped when the sides of each plank are a little higher than the middle, creating a depression in the middle and sometimes making them look worn down. Cupping affects both solid and engineered hardwood (though it affects engineered boards less), and is due to moisture and humidity.
Specifically, the volume of a given piece of wood is not static; it changes slightly depending on its moisture content. When the surrounding humidity is high, like in the summer, the wood will absorb enough of the moisture to get just a little bit bigger. When the heating is on in the winter, the humidity drops and the wood shrinks as it dries out. Gaps can even appear between the boards. When the moisture content of the boards gets high enough, they crush against each other. With nowhere to go, the edges of each board get pushed up, making the middle look like it’s sagging.
Why haven’t I hear about this before?
Most people have their floors put in professionally, and professional installers use industry-standard tools to measure the moisture levels in your house. By taking that, and the subfloor they will be installing over, into account, flooring professionals can reduce the chances of later cupping. But people who install hardwood on their own, especially without moisture meters, are more likely to see it.
Some cupping can happen no matter how carefully a floor was installed, but with the right precautions cupping may be so minor that you don’t even notice it.
What should I do?
If you have noticeable cupping in your hardwood flooring and you don’t like it, call your flooring professionals. Cupping often happens only to a few boards, so if replacement is necessary it might be quite affordable. Still, if a few boards keep cupping whenever the humidity increases, leaving them there increases the chances they will eventually buckle and dislodge other sound planks.
We do not recommend that you rent a sander and try to sand it down yourself. Doing so while it is cupped will grind away the edges where they meet, leading to an opposite floorboard condition called crowning. Crowned floorboards are convex instead of concave, with a groove where they join rather than a depression in the middle.
If you have hardwood cupping and want to talk to a professional about your options, call Unique Carpet and Floor at (703) 369-1600, or contact us on our website.