I installed 400 sq. ft. of 3/4" T&G Hickory flooring in the kitchen and dining areas. It was put over wafer board on trusses. I put down the manufacturer's required plastic barrier and then roofing felt on top of that. The boards were stapled (serrated type) through the tongue areas with a air/hammer hardwood nailer. This was 3 years ago. A month ago we had 12" of rain in 24 hrs and the sump pump ran every 2 minutes for a couple of days, and is located in the basement just below the dining floor. The door to that utility room was closed during this time, so the moisture level was probably high. The hardwood boards lifted along one line in the dining area, probably where a seam is in the wafer board. I have placed 2x4's with cinder blocks on the floor to bring them back down. I am assumming the staples have pulled out. I am considering drilling through the subfloor from below and trying to pull the hickory boards down flat, to stay. Careful measurement will be necessary to avoid going completely throught the hickory. What do you think about this idea? Should I try it before resorting to removing the boards (not damaged) and putting them back down again?

Sometimes you can correct this by putting a screw in the flooring from the bottom side. Not deep enough to go through the top side just deep enough to pull it back down. I'd use a fan to make sure it is well dried out first.

Well....I decided I had waited long enough with cinder blocks holding down my warped 3/4" hickory T&G floor from when it warped several months earlier. I tried the idea of putting screws thought the subfloor from below and pulling the boards down (while the weight still in place, 16 blocks over one seam 13' long. I used collar stops on the drill bits. I put washers under the screw heads. It appears to have worked. The final test will be next Spring when the humidity goes back up. To those who replied to my inquiry, THANKS.

Why do you not take the time before you have raised moisture levels to correct this issue so you do not have to worry about the wood floors anymore. Humidex has vent systems that pull conditioned air into the levels below the floor so humidity will stay the same on both sides of floor.
www.wavehomesoloutions.com is their web site.

Fasteners and cinder blocks is the entirely wrong approach.

Dehumidifying is the right approach.

Dehumidifying is in the plan. Don't need it until after winter is over. Problem was from too much water action in the sump pump during a really, really wet Spring and Summer. Door to the storage room where sump is located was closed, which amplified the problem. Subfloor was OK. Tongue and groove was all that warped. Pulled back down with screws from below. Keeping the humidity low in the future should keep the floor down....I hope. Like I said, it was a really unusually wet season. The water table actually came to the surface in the yard. Floated the pool liner up as well. The warped area was only a couple of 4" boards wide and 13 feet long. I am counting on the dehumidfying to keep the moisture level down so that the floor will not warp again.

If this floor was installed over OSB subflooring then of course the staples pulled out. There should have been Advantec or real plywood underlaymant for any chance of the staples holding.
Without addressing the moisture problum starting outside with propper working gutters, grade sloping away from the house, no mulch piled up againt the house, vaper barrier on the ground if it's a crawl space. Working sump pump with a cheak valve in the line going out with a the outflow ending up far away from the foundtaion.
If this is really is a OSB "wafer board" sub floor then it's going to act like a sponge, any screws you try to use below the floor will just end up pulling through and cause the floor to never be able to dry out and fall back into place.

Thanks Joecaption,
The subfloor is indeed OSB, which is the main thing now that I would criticize the builder for. It is also not as flat as I would like. I have a feeling that it got rained on before they got the roof in place. Most of the OSB seems are slightly high, even after someone tried to shave them down. I plan to install dehumidification just below the floor that let the staples go. This is the room with the sump pump. When the floor warped, the door to this area in the basement was closed and it rained 12+ inches in one day. The sump ran for days. The scews from below are holding for now. When I put down the T&G 3 years ago I put down the plastic that came with the flooring and roof felt over top of that. I have been putting tile down lately and have been using deck sealer on the OSB to help seal the top surface before putting down roof felt followed by hardiback. If I can keep things looking nice for a few more years and the market comes back, I will probably sell, as it will be about time to retire (if that's possible at all).

quote:

joecaption

I am agree with "joecaption"

You definitely need to dehummidify the area before looking at anything else. Then based on what the hardwood does after you get the inside to 40-60% relative humidity.

True Hardwoods

Thanks for another bit of advice. I have installed a dehumidifier in the basement area where the problem was. The warping happened a year ago after a 12"/24hr. rain. We had another one of those this Spring. The floor is holding. I plan to run the dehumidifier Spring and Summer. Couple that with the screws placed from below the subfloor last winter into the T&G and I will keep the faith. If it happens again, the warping that is, I will take up the T&G and replace the wafer board with plywood and then replace the T&G. But I'm not that eager for that sort of knee and back pain, so I'm not going to do it unless forced to. I wish builders would stop using that wafer board for subfloor. Thanks again.