Walnut floor installation

10 years ago

Thanks for all of the guidance we have received from this forum.

We have a house under construction. Our non-finished walnut floors were delivered prior to it being enclosed and air-conditioned. Wood was delivered about two weeks ago. Air conditioning got turned on Friday. We have been adamant that we would not allow floors to be installed prior to acclimation, but of course, there is debate about how long that should be.

We read a million discussions and see that the advice runs the gamut from a/c needs to be on for a month to length of time makes no difference, moisture content is all that matters.

We bought a moisture meter yesterday. The wood surprisingly game in at around 5%. We thought it would be higher because we're in Florida, it has rained a ton and the humidity is sky high. However, the plywood subfloor was around 15%.

So, is the goal now to get the plywood to 5%? That seems like very low humidity to me for a home in Florida, but what do I know!

Any advice would be appreciated :)

Featured Answer

GreenDesigns

10 years ago

It's not just the subfloor moisture that's an issue. A new construction home has a lot of moisture in the framing, sheathing, foundation, and every other part and piece that was sitting in the rain before it was dried in. It can take a year or more for all of that to completely dry out. Of course, you can't wait a year to install the floor! So, you have to make some sort of compromise between the ideal moisture conditions in the home and the fact that you want to finish the project and move in.

My rule of thumb on this is the I do NOT want wood flooring going in until the drywall is complete for at least a week, and the drywall should begin as soon as the HVAC is turned on and starts pulling moisture out of the structure. Drywall mud adds a big load of humidity. You want to be in the downhill slope of removing moisture, not dealing with another peak of humidity due to that adding to the load. That is, of course, on top of the testing for the actual moisture content of both the subfloor and flooring. In FL, the humidity levels will be higher than in many locations when things stabilize, so your wood's 5% is awfully low at the moment for the environment that it will live in.

The other issue would be to double check the method of installation. This is engineered wood for a glue down installation, correct? That is all that is approved to go down over slab on grade construction without doing a lot of extra prep work that hits your pocketbook hard. You cannot glue solid wood directly to concrete, so be sure of what your contractor is planning to do here.

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Comments (9)

gregmills_gw
10 years ago
The goal is to get both the planks and the subfloor to be close to equal. So if that means the subfloor needs to drop a few points. Or the walnut needs to raise a few. Theres no set rule that says one or the other needs to shift.

Right now 10% difference is a little high. Once that difference becomes closer to 5% then you should be good.

Hopefully you did this but dont just take one reading on the subfloor. Take multiples and then average it out. (As long as one spot isnt ridiculously high) and same with the walnut. Take a reading of multiple bundles and then average that out.
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maggie530
Original Author
10 years ago
Thank you very much for your advice. Quick answer to your question - it is 3/4 inch solid walnut, not engineered, nail down over 3/4 inch plywood subfloor.
maggie530
Original Author
10 years ago
Thank you very much for your advice. Quick answer to your question - it is 3/4 inch solid walnut, not engineered, nail down over 3/4 inch plywood subfloor.
GreenDesigns
10 years ago
A crawlspace is unusual in Florida! You are one of the few that can probably run your HVAC ducting through that space instead of the attic after covering the soil with a moisture barrier. It will be cooler than running it through the attic, so will be a bit better in energy efficiency.
maggie530
Original Author
10 years ago
Well, I'm back! It's been several days and our subfloor seems to be slowly getting dryer to around 12% moisture level. What's weird is that the hardwood floors don't appear to be taking on any moisture. They were about 5% when I measured a week ago and they're still around 5%. In case I didn't make this clear before, the hardwood was delivered early to our site before we could get it enclosed so it sat in 100% moist humid air for two weeks and never took on moisture. I wasn't expecting it to now that house is enclosed and air conditioned, and I was right - it hasn't. I know that my subfloor isn't going to go down to 5% moisture. Any ideas?
gregmills_gw
10 years ago
Go a head and install. Nothing more you can do. At this point your floor shouldnt have any issues. The range difference is a little high but i would feel comfortable installing.
User
10 years ago
I'd make sure that the crawl space was covered with a vapor barrier (essential for the health of the home anyway!), and get a dehumidifier into it. You're only drying out the subfloor from the top. If you go at it from both sides, it should equalize fairly quickly if the dehumidifier is strong enough.
GreenDesigns
10 years ago
I would for sure want to have a vapor barrier in a crawlspace. That's strongly recommended, and it may even be code these days??? (It should.) Otherwise, you are sitting there with your subfloor on top of a big damp spot that lets moisture into your house. Moisture from the ground is the whole reason that engineered wood was developed for slab homes. That porous concrete sitting on the damp ground just wicks that moisture straight through into the home.