Hello everybody, I hope someone here might offer some helpful advice to a serious problem developing in our new house.

We’ve just moved into a 2,300 square foot house after more than a year of construction. The full basement is poured with Arxx ICFs and has stayed nice and cool in the recent high temp/high humidty; it does not feel damp down there. We have Advantech subflooring with 1-5/8 inch concrete poured over radiant heat tubing, then another layer of Advantech, then 3-inch white ash finished with Waterlox. The flooring is stapled down, directly to the subfloor with no paper or barrier, and the builder left what seemed like plenty of room around the edges, hidden by the trim.

As the humidity built, the floor started to creak and then really crackle and pop as we walked on it. It is now humping up in various places, but especially at the entries, where the wood is running parallel to the thresholds. We believe that the high humidity is swelling the wood, causing it to expand (laterally especially) and when it reaches the edges it has come up against a stop. There are also humps at other room edges, like under windows, and we’re confident that it’s not caused by introduced water, as with rain leaking in.

The heat was up and running for weeks, maybe a couple of months before the floor was installed, so I think the subflooring was well dried. House had been closed in many months before that. The ash was kiln dried and stacked a few weeks before installation, though we did not have moisture content measured.

I have ductwork for a central ventilation system, but have not yet installed the heat exchange unit or controls. We are living through the humidity typical of summers in our part of Maine, with the windows open.

If I buy a dehumidifier as a stab at a solution, do I put it in the basement or on the first floor where the flooring issue is? Do we have to live with a shut-up house for the dehumidifier to have an effect, since with every open door or window we essentially equalize humidity with the outdoors? Will it help to get the ventilation system running in conjunction with the dehumidifier? (There is one exhaust in a second floor bath and a supply in each second floor bedroom, three first floor exhausts and two supplies, and I could install one of whichever in the basement.)

The humidity has affected all of the (as yet unpainted) wood doors in the house, opening gaps in panels and keeping them from closing, and the kitchen cabinets are all sticking too.

Any help appreciated,

Ayud