How to fix click-together wood flooring that slides

By Jeanne Huber
Wednesday, March 9, 2011; 2:44 PM

Question: I had a three-eighths-inch-thick, click-together wood floor installed over two layers of vinyl in my kitchen less than a year ago. The wood is sliding lengthwise in two areas. It has unlocked in one area, and socks snag on some of the joints. The installer fixed it once, but the problem continues. What is the best way to fix this? Is the problem that it was installed over vinyl, or something else? --Fairfax County

Answer: The problem isn't the vinyl, which acts as a moisture barrier and prevents problems stemming from a damp basement or crawl space.

Dry air is the more likely cause, particularly if the problem occurs only in winter. Click-together flooring at that thickness typically has a core made of high-density fiberboard, a kind of particleboard. Like all wood-based products, it expands when surrounding air is damp and contracts when the air is dry. The individual wood fibers move mostly in width, so if you had a traditional solid-wood floor, you'd see gaps along the sides of boards. With particleboard, though, fibers are oriented randomly. Your flooring is sliding lengthwise because the biggest change occurs in the direction where there is the most material.

Other issues may be compounding your problem. For example, the moisture level of the flooring may have been too high when it was installed, which would magnify the effect of dry air in the winter. Or a beam under the floor could be acting as a pivot point, encouraging the planks to unlock. (Click-together flooring isn't suitable for floors that sag more than one inch in six feet.)

What to do now? Frank Kroupa, technical adviser for the National Wood Flooring Association (, recommends buying a $20 hygrometer and monitoring the relative humidity in the room. The flooring should behave if you keep the reading between 30 and 50 percent and the temperature between 60 and 80 degrees, he says.

You may need a humidifier in the winter. An air conditioner acts as a dehumidifier in the summer. If the problem persists, Kroupa suggests using fine sandpaper to carefully round over sharp edges where socks snag. You can also plug gaps between boards with a matching color of a material that remains flexible: silicone caulk or oil-based putty, the same material sold for patching nail holes in prefinished flooring. (Color Putty and DAP Finishing Putty are two examples.)

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