How to fix engineered floors that warp

'Floating' variety needs room to breathe

Q: In January, we installed floating bamboo engineered flooring over our concrete slab. The slab was poured the previous July, and in-floor radiant heat was added. We primed the concrete and added felt underlayment before installation.

The flooring in one of the ground-floor rooms is beginning to buckle. It started when the weather warmed up and we no longer needed to use the radiant heat. Did our zeal to create a tight fit create the problem? The floor was fitted and then stabilized with wedges at the wall, and then quarter-round trim was installed at the baseboards to ensure it didn’t come apart.

My idea is to pull up the quarter-round, take out the wood shims we put in and let the buckling level out. But does this mean that next winter the floor will come loose?

We did not nail any of the planks into the slab because we had no way of knowing where the radiant tubing is and obviously we can’t chance a puncture.

A: Floating floors are meant to do exactly that — float on the subfloor. Nailing the floor to the subfloor or wedging the edges at the walls defeats the purpose.

As the floor expands and contracts with temperature and moisture variation, the floor moves. If the floor doesn’t have enough room on the edges, it will buckle.

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Radiant heat is very comfortable heat. But in this case it is contributing to the floor failure. The tubing in the slab carries warm water. When the heat is on, you are heating the slab somewhere in the neighborhood of 68 degrees. In the summer, the heat is off and the slab reverts to the temperature of the ground — about 55 degrees. The variation in temperature causes the flooring to move and eventually buckle.

Individual boards are either manufactured with joints that lock when driven together by the installer or tongue-and-groove joints that are glued during installation. Either way, the installed floor becomes a monolith.

Once you give the floor room enough to float as it was designed to do, the buckling should cease and the floor will flatten out. There’s a good chance that the joints won’t separate if they are the locking type. If the floor is joined with glue, the buckling may have compromised the glue bond and you may have to take up the buckled section of the floor and reinstall it.

First, remove the quarter-round molding and then the wedges. Wait a week or two before replacing the quarter-round to allow the floor to reacclimate. Consider replacing the quarter-round with base shoe molding, which has a skinnier but higher profile. That way you can easily nail it to the wall and not the floor.

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