Flooring Inspection Safari: Swollen Laminate Seams

swollen flooring seams

If you have a wood or laminate floor in your home, you must be aware that water is not a friend of your floor. You should quickly clean up spills. You should use only a DAMP towel or cleaning pad when you maintain the floor. And you should absolutely NOT use any type of wet-jet or steam mop on these floors! The story that follows illustrates what happens when excess water meets a wood-based floor.

I looked at a laminate floor that had been sold for use on two floors in a townhome as a “commercial” quality by a big box store. The homeowner complained almost immediately that she saw “bubbling” along one seam near the kitchen in the dining area. She complained for the next two years that more and more seams showed this problem. The installers looked at the flooring and said that the “bubbling” (what we in the industry call swollen seams) was from excess water. The homeowner would not accept this explanation so the store asked me to take a look at the floor.

The Mrs. was adamant in explaining that she cleaned the floors using a damp, wrung out cleaning pad and flat mop. If she needed something stronger, she lightly sprayed on Bona cleaner, recommended by the retailer. So far, so good.

I found eight boards with swollen seams near the slider and in the nearby dining area on the main floor. I checked the stairway and upstairs hallway and office. All of those seams were perfect.

The laminate was properly installed. I found the correct plastic moisture barrier over the ground level concrete subfloor. The correct underlayment (pad) was laid over the plastic sheet. The floors were flat to tolerance. The distance between end joints was correct. I was able to lift baseboards and saw that the installers had left expansion gaps around all the room perimeters as required. Most importantly, I used a special non-destructive moisture meter to check moisture levels under the floor in all the rooms. All areas were in the “low” range, well within tolerance. I also used a pin meter to check moisture in the swollen seams themselves. (As the name implies, this meter has two sharp pins attached to a meter. The pins sense moisture amounts and send this information to the calibrated meter.) The readings were also low — no detectible moisture.

So what does this mean? The only way seams swell or blister is when water gets into the seam from the top of the floor. A tight seam makes the water sit outside the seam for a while, giving you time to wipe up the spill. But eventually, especially with a lot of water, the water gets into the seam. Any wood swells with added moisture. A laminate plank is made with a compressed wood core. Every tiny piece of wood has a comparatively large surface area. When enough tiny pieces of wood absorb enough water, the wood swells and blisters or bubbles show up along the edges of the seam. Over time, the wood dries out but the swollen edges remain.

Most of the swollen seams in this home were near the sliding door. Maybe the door was open during a rainstorm and the floor was soaked. I can’t pinpoint the cause of the water. But I do know the effect that water has on a wood-based floor.

Who is Glenn Revere?

Glenn Revere has been a carpet expert since 1973. He’s a certified flooring inspector and the author of All About Carpets, the only book written to protect and inform you about your carpet choices, from carpet buying and carpet warranties to carpet care and maintenance. You can find him on FacebookGoogle+ and Twitter.

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