Only becomes crowned after the wood dries out. It can look cupped if the floor is tight, gains moisture from anywhere and the compression set happens. So if the floor gains moisture, it wants to move. The adhesive prevents some movement and the edges get crushed and peak up; compression set. However, I'll still bet it's from the concrete below.

Dubro said:



How do you KNOW that? What tests where done to verify this statement?

I believe Mapei states to use their 990 for exotic species but that would not cause cupping.

How wide is this flooring?

Are you using any ventfree gas appliances such as gaslogs?

I have read that slab temperatures can reach a dewpoint and cause cupping. I would investigate that angle further.

The Mapei product (Mapei Planiseal WFM) says that it reduces the moisture to below 3 lbs. That's why i said it is not comming from the slab. I have not proved that to myself. Is there a way to prove it? I am not using any gas logs or any ventfree gas appliances. The boards or 3/4 thick and 3" wide.

I bought a Frigidaire dehumidifier. How long does it need to run before I should see some effect from it. I have it set to 35% The humidity in the house is down to 35% - 40%

Check out my gallery. I added some images so you can see what I'm talking about. Thanks.

edited by admin: pictures added

I think Dennis touched on how to conduct moisture readings from the top and bottom. Wood cups when the bottom side is wetter than the top. I'm not an expert but Planiseal would have no bearing on whether the temperatures underneath the wood can reach a dewpoint. Call Mapei tech support and get their input. I don't see many slabs where I live.

Thanks, I'll call Mapei tech's and see what they will say.

What is the name of the gauge that I should get that can do an invasive moisture reading on the bottom of the boards. If anyone knows where to buy a good one that is inexpensive please tell me. thanks.

Thanks for the photos; they help. IMO, the cupping is slight and not severe. I say this based on what I can see in the photos. But sometimes, photos cannot show the full extent. So the floors may appear to be less severe than they really are.

It's is recommended to test concrete for moisture whether or not one uses a "moisture barrier" or not. I would have recommended testing prior to the application of the Planiseal WFM and afterwards, to verify exactly what is going on. But since that does not appear to have been done, we'll need to try to deduce what is happening. And to do that, you need a inexpensive humidistat/hygrometer and a quality moisture meter. The Tramex Moisture Encounter is the most widely used and recommended. You can either buy new, buy used, or hire someone who has one. They are not cheap. But you can but a cheap hygrometer at many places.

The moisture meter will read the top of the wood, the bottom of the wood and the concrete. If the bottom of the wood is higher than the top ( or surface ), then there is your cause of cupping. You may not be able to do any testing without removing a couple of boards. You can also test boards left over and compare them to the installed boards. If there is a big discrepancy on the bottom of the boards, again, there is your answer.

Many flooring manufacturers consider 45 to 50% relative humidity ( interior ) to be the ideal. Using the humidistat, determine what yours is.

Finally, your floor looks to be a sanded in place floor. If after all this testing, you still cannot determine the cause exactly, then wait a year or so and see what the floor does. If it does not get worse or even gets better, then you could just leave it alone. Or have it re-sanded to flatten it out. Do NOT re-sand now. The floor must fully reach an equilibrium to it's environment before any repairs should be attempted.

The pictures are pretty accurate. It's not that bad but I tried to take every precaution possible to have the job come out perfect. I tested the concrete before I started and it was 5 lbs. That's why I had the vapor barrier installed. I should have tested afterwords but I didn't. The Mapei Paniseal WFM looked so good that it didn't cross my mind to test.

I called Mapei Tech Dept and they said the cupping is probably due to not climatizing the boards long enough. They were in the house 2 or 3 days before they were installed. And then the contractor ran out of boards. When he got new boards and brought them in the house I questioned him how could he install them so fast without climatizing them and he said he did a moisture test on them and they were within spec limits and it was ok to install. I'm not a professional installer so I trusted him.

I will find the meters and buy them so I can do some testing. Instead of removing a couple of boards can I just tap a couple of finishing nails in almost to the bottom of the board and test that way?

One final question: What is the best way to keep humidity at a constant 45 - 50% The portable Frigidaire dehumidifier that I bought is very noisy and is running constantly because I have it set to 35%. My electric bill will probably be very high as well.

well, you should be starting to use the heat more and that will work to help dehumidfy the air as well. So once you start that and get the space to 45 rh then it wont run much at all untill you stop running the heat regularly. Keep in mind that it took months for the cupping to appear and it will usually take close to the same time to relax back down. I had my dishwasher take a crap on me about 3 months ago and when I put in the new one I got the drain line connection loose. It slow dripped for about a week before I saw the floor start to cup. I fixed the leak and the floor continued to cup for a nother week before it started to dry out and stop moving up. its just now starting to get flat enough to where you can hardly feel it when you slide your foot across the area.

The picture shows compression. Just the edges.

The floor gain moisture from the air after installation. Acclimation.
What was the woods moisture content on the day it was installed?
What is the woods moisture content, now?