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Ask the Expert Question-and-Answer Archive

by Ron Joseph

September, 2008

Refinishing Hard Wood Floors

Q: This summer I pulled up the carpet to refinish my hard wood floors and the floors were flat. I sanded it down and the wood looked like new, so I stained them and it took 6 days to dry (I thought that was a long time). When it was dry to the touch, I put 4 coats of polyurethane and it was fine for a few weeks. Then I noticed that the floor started warping, not real bad but I could feel it on my feet. Then about a month later I noticed the clear coat was coming up in some areas. The house does hold water under it, but the area of the house where it holds water the most (an area that the previous owners already refinished) isn't warped or anything. I think it might have been the time of year I stained and polyurethaned it. I live in south Louisiana, where its hot and humid.

A: Without seeing the floor and inspecting the polyurethane finish, I can't tell you exactly why the paint is coming up, but moisture in the wood is definitely a possible cause. Paints must be applied to wood during somewhat dry weather. Paint manufacturers suggest that the moisture content of wood should be below 12%, but in a humid area such as Louisiana a moisture content of 15% might also be acceptable. I doubt that you measured the moisture content since you would have required a special instrument to do so, but that is the general wisdom for painting floors.

The other possible cause is that you applied four coats of clear polyurethane too soon after each other. You need to wait long enough for the water or solvents in the polyurethane to evaporate. If water or solvent in the clear coat could not evaporate fast enough before you applied the next coat, this could be the cause of the lifting.

I hope this helps.

Ron Joseph

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