Q: We are in the final stages of having red oak flooring installed in our home. We chose to have a water based varnish applied vs. the oil to allow more of the true wood colours to show. Prior to application of the water based varnish the floor was smooth and level. Subsequent applications of varnish have resulted in slight cupping in the flooring.

The installer has indicated that this is a result of humidity getting into the flooring material. The thing I don’t understand is why didn’t this show prior to the varnish being applied? The project was started in early July with the flooring material having been nailed down in place for two to three weeks prior to the first application of varnish. Prior to that time the installer left the bundles of lumber in our house for 10-14 day so it could become acclimated. Had we been advised that the water based product could result in cupping we probably would have made another choice.

What if any alternatives are available to us? The installer has indicated that it (the flooring) will probably lay down more later. Could this have resulted from improper application of the varnish by the installer? We have a beautiful but wavy floor.

We moved into this home in Sept-81. The oak plank flooring is installed over ¾ plywood sub floor with a crawl space. The crawl space has heavy plastic over the earth underneath. Prior to the red oak plank flooring we had Ash parquet flooring that was installed in ’81 which gave us no problems.

A: I have known water borne finishes to cause cupping. It is important when using these finishes to vent the area and cause the small amount of water to evaporate away from the floor as soon as possible. This also means allowing time for each coat to properly dry before applying another, and following the recommended spread rate. I would check the humidity in the area, at floor level with a hygrometer, and if excessively high, get a dehumidifier or fan blowing. Heating season is almost upon us, and hopefully, with the furnace running, the floor will flatten out.