Q: Dear Woodfloor Guy, Due to severe damage in my house, I recently had new oak floors installed on the second floor of my home I live in a hi-ranch in NY. My problem is since the installation 5 months ago I have had many large sections or areas of the second floor that have cupped.
I put the contractor on notice and he came to the house and he admitted there is a problem but could not determine what would cause the cupping. He had his moisture meter and found everything dry. PS as a side note the wood did acclimate to the house for 3-5 days inside prior to installation. The floors are a #1 oak and were finished with 3 coats of satin poly. The installation was very tight board to board, no gaps. Now knowing that the only thing that has caused the cupping is expansion due to absorbing moisture. And it did not absorb moisture from the surface because it’s sealed.
My question and this is reaching a bit but at home depot etc. I’ve seen the pink rosin paper used for under hardwood floor installation. My installer used tar paper. Is it possible that due to the heating and cooling of the house/floors that moisture could have built up or condensed under the hardwood floor between the floor and tar paper and due to the fact that tar paper is a complete barrier that the moisture could not escape? And as a result the condensed moisture was absorbed back into the hardwood floor causing it to cup?
A: OK, so this floor is on the second level, and not above a ground level crawl space. Is that correct? Was this severe damage caused initially by a flood? If so, and if the sub floor at the time was not replaced or completely dried out, that is the likely source of the moisture that would cup your floor.
I think the use of tar paper is irrelevant. It would not matter what was used. If there is an imbalance of moisture in a structure, for example a sub floor, that moisture will migrate to the exterior of the plywood, then through the wood until both products are stable. My guess is that either your sub floor was not dry to within 4% of the hardwood, or possibly you have a leak, either from the roof area, or perhaps a plumbing leak that may run down the walls and then under the floor. If it was a slow plumbing leak though, I think you should see some evidence someplace on a wall somewhere with paint peeling.