I had a hardwood floor installed in my new home approximately 4 months ago. After the floor was finished, I covered it with paper to protect it while completed finish work. When I pulled up the paper, I discovered the floor had began to “cup” throughout the house. It is not horrible, but I would like to see it lay flat again. I began to wonder if I had a moisture problem in my crawlspace. I found everything to be fine in crawlspace. The vapor barrier was intact, no standing water, and adequate ventilation. The house was unheated after floor installation due to summer weather. I have checked moisture levels in subfloor, floor joists and hardwood itself. Everything seems to be within normal limits. We also checked all moisture levels prior to installation and floor had approx. 2 week acclimation time. The house had been dry to weather almost 1 year prior to installation. I have begun heating the house with my woodstove hoping that the dry heat will lay the floor down. My questions are:
1). What do you think is the cause?
2). Can I use a dehumidifier inside house without cracking sheetrock?
Replies
How was the floor fastened? What is the plank width? You should be fine to run the DE-hum inside the house, as I have to all summer in my home.
The plank width is 3 1/4". The floor was fastened with manual floor nailer through the tongue.
What do you think is the cause?
The cause of the cupping lies in the moisture realtionship in the boards - - likely the top of the board is drying out further while the bottom isn't - your wood stove will make it worse, since you will have very dry air circulating above and relatively cool moist air below - use your dehumidifier in the crawl space since it is impractical to move your woodstove there :-)
is there tar paper or vapor barrier between the sub-floor and the hardwood?
Yes, we have tar paper between subfloor and hardwood.
The place you need the de-huimidifier is in the basement/crawlspace.
You say all the components are within acceptable limnits. The results say apparently not. You have more moisture to the bottom of the boards than the tops so th eboards are growing on the bootm and/or shrinking on the tops.
You mention acclimatizing for two weeks prior to installation. That is a norm but it means nothing if moisture levels are not stabilkized in equilibrium with the environment. What are the hard numbers on all these readings you have taken?
Excellence is its own reward!
My subfloor prior to installation was primarily 12% moisture content throughout the house with a few spots at 14%. The hardwood was 8-10%. I was told a 4% difference was acceptable.
My first step was to dehumidify the basement, but I feel like I am wasting my time. I remove moisture from the crawlspace everyday, however I feel like I could be pulling moisture out of footings and/or air in the crawlspace and not the from the subfloor. I took moisture content readings in several locations in the crawlspace of both the TJI's and subfloor. I have compared the readings once after 2 days dehumidification without any change noted. I will continue to take readings in the days to come.
thanks!
By the time you drive a couple thousand flooring nails into that tarpaper, it is less of a vapour barrier than you might think.
Since you have a new home, that new concrete is off gassding a lot of water vapour. Sealing it can help a little.
You had a diff of 4% moisture content when you laid the floor. Doesn't sound like much, but the diff between 8% and 12% is a 50% increase.
I rebuilt a house in 98-99 that haad crawlspace moisture problems which we minimized but because of hardwood floors above, I added a de-humidifier to the project for the crawl. After two years, all was fine, they hadn't seen any moisture in the crawl for all that time, and the floors were nice and flat so they assumed they could turn it off to save electricity.
Guess what.
Floors started to cup within two months or so. They waited six months to call me. I immediately went to check on whether the de-humidifier was still working and was not all that suprised to see it was unplugged. Ensuing conversation brought out their erroneous assumption. We re-started the dehumidifier and the fl;oors have not gotten worse, but they have not gotten any better either.
I believe that if bothe your subfloor material and your hardwood were in the range of 9-11% when laid, you would now have no problem. Keep running the de-hum to keep it from getting worse. Seal the underside somehow..
Excellence is its own reward!
Would placing a 6 mil vapor barrier to the underside of the floor joists help? I have a similar problem.
That could be a solution.
You need to be sure where the moisuture is coming from and seal on that side. But you almost never want to use a double VB with space between to have the potential to trap water vapour. For instance, if you have kraft or foil faced fibreglas insulation with the vb side on top, you would be sealing moisture between the krat and the plastic, creating a home for mold etc..
Excellence is its own reward!
Sinde you have a vapor barrier on the underside of the flooring, I doubt that dehumidifying the crawl space will be of much help. I just wonder if the paper accelerated the drying of the surface of the wood.