More on warping floors

Q. My floors are buckling. I was in the middle of putting on an addition when Sandy hit. My crawl space filled with water. I had two inches on the first floor, so I needed to get the wood floors replaced. Our contractor put down oak floors and insulated the crawl space, but now we learn that he put tar paper under the oak floors, over the old plank subfloor, and left out the vapor barrier in the crawl space. He said he did this so the floor could continue to dry out and breathe. Now the wood is cupped and the air-conditioning people are saying to lower the temperature of the thermostat. What went wrong and what should we do?

A. This is part two of the answer to your question. Last week I observed, during a consult at your home, the cause of your problem. You have a vapor barrier installed in the wrong location, on top of the unfinished subfloor planks instead of underneath them in the crawl space ceiling. Normally, using vapor barrier-faced insulation, the vapor barrier would be attached right against the bottom of the subfloor, in the ceiling of the crawl space, so that all I would’ve seen would be the cotton candy-like insulation, held in place by special bowed rigid wire. Instead you have no insulation where the air conditioning ducts are, and no vapor barrier.

You need to pull the insulation down and install a vapor barrier, which must now be a breathable membrane. Several manufacturers make roll-out material, ordinarily used for wrapping house sheathing prior to installing siding. If the membrane doesn’t breathe through microscopic holes, moisture will be locked between the two barriers and the floor-cupping will be even worse.