Moisture Causes Cupping In Robbins Prefinished Wood Floor


We installed 2-/4″ Robbins prefinished wood flooring to the tune of about $6.80/square foot. At first it was beautiful then it cupped. We have exhausted ourselves trying to get somewhere with the company. I mean one room is not enough for them to bother themselves. They did come out to the site and the predictable response was that they are not accountable and to put a dehumidifier in the basement which we did but the cupping remains. Any suggestions? I hate to have to try to take down the supposedly 10 layers of aluminum oxide. Just wondering what you would do. Perhaps we should just live with the problem..



Dear Mary

Wood floors only cup when there is a difference in moisture content from one side the board to the other. It certainly could be dampness in your basement, but I’m not sure that this would be the time of year when your basement would be damp. Have you had and unusually wet winter where you are ? De-humidifiers work best in warm summer weather and tend to freeze up in the winter when temperatures in the basement are low and the humidity is low, because of a furnace down there.

The hardwood floor will cup when the moisture content is more on the top of the floor surface, than the underside. This would make sense in the winter when the basement furnace is drying out the underside of the floor, whereas the living space is kept humid within the 40-60%. And then it will bow up in the middle of the hardwood board when the opposite is true in the summer. Damp basement and dry air conditioned air in the main room. And prefinished floor are really susceptible to this because they are not sealed with a finish at their seams. You might also question the installer as to the moisture content of the wood when it was installed, and ask if they checked the moisture content of the subfloor, were the two with 4-5% of each other ?

In oder to prevent this from happening the new floor should have been installed on a thick plywood subfloor (1″ is best) so that the bottom side moisture would not have affected this so much, as the floor nails (I hope they used nails and not staples) would not penetrate the plywood, thus saving it from any moisture migration from below. Also if the floor is installed on a OSB or particle board subfloor this could be causing problems also.

So it would be best to not sand the floor at this point, as you may find that by spring and with a dehumidifier the cupping may diminish a bit. But it probably won’t go away entirely. Sometime in the summer you should think about sanding the floor flat again, but this time make sure you have no dampness in the basement winter or summer, and try to keep the indoor humidity level to about that magic 40-60%. Below and above.