Hi Everyone,

I'm wondering if this scenario makes sense to anyone and if I have any hope of a nice floor.

I recently had an addition put on my home (Southeast Michigan) and used 2.25" red oak site finished flooring to match the existing 1953 house. The flooring was installed late April of this past year and sat unfinished until July due to cabinet delays, etc. The addition is on a 36" unvented crawlspace with some vapor barrier (doesn't completely cover bottom of crawl) and some rigid foam insulation on the walls. Band joist areas are completely uninsulated.

Everything was great during July, August, and September. A few weeks ago I noticed I'm starting to see some cupping on the boards (minor, but it's there). My limited knowledge tells me I'm pulling moisture from somewhere. I would have thought this would have occurred in the humid summer months, not as my inside air is drying out from the furnace. I had new flooring installed over the new crawlspace as well as the existing basement. It's significantly worse over the crawlspace.

Any ideas of what I should be looking at? Moisture in the crawl? Add humidifier to living space (currently GFA furnace humidifier is inoperational)? Yell at flooring contractor (might not solve anything, but I'll feel better)? I placed a probe in the crawl and it was reading 62 degrees and 69% humidity. First floor is around 70 degrees and 50% humidity right now. If that helps. I wasn't around when the floor was installed to know if a moisture check was done.

Thanks!

sounds like top of flooring dried too fast for underside, which is still retaining higher moisture levels..

dont know what the weathers been like up there, but here in NJ its been brutal..66 inches of rain this summer and fall..ground water tables, floods..you name it..a hurricane and Noreaster or 2..you can imagine issue arising in floors...no?

dry out your crawl space..

well you answered your own question but let me clarify whats happening a bit. Your floor stayed flat up to this point because you had a similar temp/rh inside the home and in the crawl space. Now that you have started to run the heat the interior r/h drops but the crawl has not. Wood that has a higher moisture content on top or bottom will shrink/expand untill it reaches an equilibrium. So your heat is probally drying the top out and the bottom has stayed the same. the imbalance is the problem not the installer. Either dry out the crawl or humidify the interior, for floors to behave they need to be kept 4o-50 % r/h above and below.

The cupping is minor now (wife didn't even notice it) and I can likely live with it.

So, I'll plan on turning on the furnace humidifier and running the crawl dehumidifier. Think there's a good chance I can reverse this?

Thanks for your help. I just don't want to do anything that will make it worse.

if its slight and just recent then there is a good chance it will lay back down once you get everything in check. Just fyi those whole inline humidifiers only work when the furnace is running lots of time thats just not enough, but that again depends on the size of the unit vs the size of space. One idea if you crawl space is inclosed many people are just treating it like a basement and running a supply and return vent to the crawl space. I know locally there are a few companies that specialize in drying out crawlspaces, b-dry,master dry ect.

This is way too easy! Your unvented crawl space is the problem.

Since it is unvented, you need to have a dehumidifier in the crawl space.

The bottom of the boards are wetter than the top. As the temp, drops the rH in the crawl space will increase.

Your floor joist and subfloor are going to dry rot, if you don't get a handle on the elevated moisture in the crawl space.