I think the house was built in the 50's and these seem to be the original wooden floors. 2.25" wide, 1/2" or more thick. Located in southern Louisiana. I sanded them down and put 3 coats of oil based poly on them about 3 years ago when I got the house. The floor was level and fine then. For about a month or so, I've noticed a little waviness in them, and it's gotten worse over time. I opened a guest bedroom we don't use and the door hit the floor. It was buckled up about an inch or more. From everyone one I've talked to, they said it's moisture under the floor. We inspected under the house (it's raised about a foot or two) and there's no water line leaks and no drain leaks. It sits on a hill and water drains away from the house. No water was under it standing. It was pretty damp with mushrooms growing under there. I'm thinking it needs more vents cut in the brick to allow better air flow and for it to dry out. I cut that one section that was really bad and there's tar paper under the oak and then solid tongue and groove boards as the sub floor. The oak is dry, the tar paper is dry and the sub floor is dry and not buckled. Could it be the humidity inside the house? I insulated it very well when I got the house and installed a new AC. The AC don't run that long to cool off the house. Maybe it's too insulated and the AC don't run long enough to remove the humidity? It's about 65% humidity in the house right now. I have some picture if that would be helpful. I'll see if I can find a way to link them here or attach them or something. I'm also thinking of putting flow fill grout under the house to keep moisture from the soil coming up. I've talked to a few people around here and they said that has helped. Thoughts/suggestions on this? I have to get ride of the moisture under the house before I can fix or replace these floors and I don't want it happening again. Thanks in advance!

Cory

It appears that you have created too much of an imbalance between the relative humidity above and below the flooring. You seem to have reduced the relative humidity inside the house with insulation and AC. (Just as aside, when the AC cools the house without getting the humidity down it's usually because the AC system is too large). Concerning crawl space ventilation, the building science recommendation has changed over the years and the recommendation (for certain parts of the country) now is to close off ventilation and condition the crawl space as you would the living space. I'm not sure where Louisiana falls in the crawl space ventilate/not-ventilate, but it seems that based on the high humidity level there you may need to enclose it and control its moisture in order for your floors to be happy. To control ground moisture, polyethylene is laid on the bare ground and run up the foundation walls and sealed. That may be a good starting point. Then see if more ventilation of the crawl space helps.....if not then seal it up and let some of the conditioned air from the house get down there. I'm in the northeast so my suggestions about what to do in your part of the country may not be accurate.

Are you sure that your floor is"buckling"? That is when the fasteners start to come loose. If you only have cupping is is most likely caused by the seasonal high humidity. Warm air holds more moisture and the floor is susceptible to absorbing the humidity which will cause the wood to expand. The tops of the flooring touch before the bottom which causes pressure that cups the surface. Cupping will usually return to a flat surface when the flooring dries out. Much more pressure will cause buckling which will never go down since the fasteners have been pulled loose.
Hopefully you only have seasonal cupping.