Four years ago I decided I wanted wood floors. I got a recommendation from a friend and judging by his beautiful floors I called the contractor. We decided on a 3 ½" Red Oak floor to be installed over my concrete slab, just as my friend had installed.

My home is in the Dallas area, its about 20 years old. I purchased it as a foreclosure so I didn’t know anything about the history of it. One thing I found concerning was water stains that I found on the baseboards in various areas, the home inspector couldn’t explain where the stains had come from. I had a plumbing test performed and no leaks or problems were found. In the end I’m confident that what had happened was a one time event, the garden tub had over-flowed. I’m confident because in trying to figure out my cupping floor I have had everybody and their brother out to look for water intrusion, chimney people, plumbers, drainage company, etc. and no source of water intrusion was ever found, there was never any indication of ongoing water problems.

The existing flooring had to be taken up, the contractor had his people take up the ceramic tile and I took up the engineered wood floor. When I took up the flooring I found a place under the vapor barrier with pooled water (had to be from the garden tub flood) which I mopped up. I immediately called the contractor and he came over. I showed him where the water had been and he drove 2 nails into the concrete slab and attached a meter to the nails and said “its to the high side of normal” and I asked what does that mean and he replied “its normal” and I said so… he replied “we’re good to go”. I monitored the spot and there was no indication that there was an ongoing problem. Two days later his workers installed the floor. Heavy plastic over the concrete foundation, then 5/8” plywood, then felt, then 3 ½" red Oak flooring planks.

He came by after the installation was complete and walked the floor with me. He explained that the floor would have to acclimate for 2 weeks. He also said a couple of things which concerned me. He said that he had a hard time finding the flooring, that his regular source was out (that got me to thinking, so you’re using product from a distributor you’re not used to doing business with?) and while walking the floor he said that the nickel width gaps I saw in the floor every 6-8 feet would swell shut… it never did.

When he returned 2 weeks later he was confused by the gaps and that they hadn’t shut. He said it would’t be a problem, that he’d work “his magic”. His magic consisted of filing the gaps with putty.

My wife and I went on vacation so we would not be exposed to the fumes. When we came back we were very happy with what we found. Beautiful smooth sanded and stained wood floors, at least until the cupping started.



We were never told a thing about RH or how we should maintain the floor, absolutely nothing. I contacted the contractor within six months (contractually he wasnt responsible for any cupping after six months) because areas of the floor had started to cup. He returned and said that it wasnt really that bad and that some movement should be expected. He did say though that because most of the movement was in the area where I had found the pooled water that we could consider taking that part up and sealing the slab, but that that process also came with its own problems, because disturbing the integrated nature of the flooring system could bring its own problems. I said lets just wait and see what happens...he said that would be fine and to contact him if I felt like I needed to. I did, but he never responded, he made himself unavailable.

I started to think that maybe the fault was mine so I had everything imaginable checked into as a source of water/moisture that could be causing the floor to cup, but in the end never did find anything that could explain it.

I noticed that the cupping happens mostly in the winter and decided that the problem might have to do with the RH in my home because it gets awfully dry during the winter. I am in the process of correcting that with humidifiers.

Everything I have read about the subject indicates that when things dry out that gaps in flooring should occur and not cupping. This quote from a flooring site indicates just that: "...make sure you understand that if your home dries out in the wintertime expect to see cracks in the floor unless you take care to make sure the relative humidity stays stable. On the other hand if the relative humidity rises expect to see the floor begin to swell and possibly cup unless you can control or lower the humidity during the more humid season."
My problem is just the other way around, when my RH drops in the winter the floor cups.

The return for my HVAC system is very near the area that cups so maybe that isn’t helpful, but it also is the area that I found the pooled water, or at least close to it.

So I’m left wondering why the floor cups during the dry season?
During the summer the floor returns to normal, well more or less, normal for this floor is always a little cupped, but it gets better to the point that I think to myself “why was I ever freaking out about that”, just to have winter return and I’m back to freaking out. This winter the cupping area is about 6 feet away from where it cupped last year, but still in the same HVAC return/pooled water area.

Why the cupping during the dry season?

Sounds like he did everything to industry standards. Dry cupping is normal.

The gaps are kinda weird, wondering if he checked the MC with a meter before installing and acclimated it long enough. Making certain the rh is about median levels for your zone is important as well.

As for the water pooling on the slab, I would have gone a step further and applied Bostik MVP4 or equilivent vapor retarder under the plastic.

If he fastened the ply to the slab then he punctured the vapor retarder ie plastic. Never could figure out why guys do that.

I'd get Perry Wright over there or some other inspector to check it out.

Thanks for the quick reply,

He did nail the ply. As a matter of fact I remember the quote..."no less than 20 nails a sheet".
I've had a lot of replies like your's indicating that as soon as you shoot through the plywood you're defeating a vapor retarder.

I've had a company out, supposedly a reputable company, certified by the NWFA and the kid that showed up was pretty noncommital. He drove a test spike (nail) into the wood, connected his meter and said it was within specs. He said they could attempt a repair, or to be more accurate a replacement of some portion of the floor, but as the installer said that could bring problems of its own. The kid said "it might just go back to normal over time", which it actually did, more or less.

The current cupping is in a small area, but wow! is it cupped.

I have been monitoring my homes RH like a hawk. Before I came to the conclusion that the RH might be the cause of this problem I didnt give it a lot of thought, but now that I do I have noticed significant swings in the RH of my home. Two weeks ago I purchased a thermometer/humidity meter and the initial moisture % was 21. Clearly that was LOW! I purchased a humidifier (small vornado brand for the area) and it made a difference, or at least I thought it did but really it was the 2 days of rain, after the rain the numbers dropped again. Clearly I need a whole house humidifier, the tiny Vornado isnt making enough of a difference.

I wish I had a nickle for evey dollar I've spent in products (chimney cap, HVAC improvements, humidifier) and services (plumbers, chimney company, drainage consultants) to mitigate this problem.

This floor is the majority of my downstairs in a 2 story 3500 square foot house. It seems like I need to be looking at a whole house humidifier...?

I have a picture of a humidifier I own in my blog on my website....oh wait....there should be one on hardwoodinstaller.com as well. But I think Ken took it down.

Anyhow, it does over 2,000 sf and runs independently. Digital display. I've even drug it out to jobsites.

Here's a link: http://www.amazon.com/Essick-Air-4D7-30 ... B0000TPRM2

This is just a guess from my computer.

Has anyone checked slab temperature in the areas of concern and the areas not effected?

1.) Hot water line running under the area, causing a dew point flash on the concrete. Enough to pool water?

or

2.) Grading around the property, allowing water over the slab, during a storm, in an area and it runs to the lowest part of the slab and pools?

my guess is the plywood he nailed was not within spec of moisture content in conjunction ot the flooring which should be within 2 percent..

the heating season is pulling the moisture from the plywood and releasing it to the flooring.

Do a search with your last name and you can find where things are. It's in the acclimation page.

http://www.google.com/cse?cx=partner-pu ... .q=perrera

Thanks for the replies,

Its quite a puzzle to be sure. The cupping is always within about a 10 foot area. Last year it was over by a bookcase and this year that has relaxed and looks as if it never had a problem, but the area cupping this year is at the entrance to my master bedroom directly under one of my HVAC returns....BAD cupping, the worst ever for this floor.

The riddle that is this floor seems to have one consistency and that is the fact that it really only does this during the winter. My thinking initially was about slab temperature and condensation, this floor cups when it gets really cold for an extended period. I mean like for about three weeks we've had 20 degree nights and 30 degree days, and that is cold in Dallas, and the next thing I notice is whamo, the floor is cupped like nobodies business. So is it the cold, or the heater running constantly, or both, maybe also combined with inconsistent moisture levels of the slab/ply/wood at the time that the floor was installed.

I dont think its water intrusion from grading as I have checked that thoroughly, besides we're in a drought, I dont remember the last time it rained.

floormeintucson, I purchased the humidifier you recommended, works quite well. The best it can do is 43% humidity in my home running constantly. I backed it down to 40% and it runs a lot but certainly not constant. I dont want to swing too far to the side of high RH and cause other problems, so hopefully 40% will help.

Heres a pic:

Considering we haven't found a solution, I'm going to throw the fireplace into the picture. Heat expands stuff. Perhaps something is going on there?

I havent had a fire in it in 2 winters.
Last year I had a fireplace company come out and look things over, I was afraid maybe water was getting in behind the roof flashing or down the flue. The old timer that looked it over said everything looked fine. Just to be sure he built a custom cap and water proofed the brick and made sure the flashing was good. Its masonry from bottom to top.

He said it was doubtful that was the problem as the fireplace and chimney was in great shape.

I'm telling you I've had everybody and their brother out here to tell me what is going on with my floor and I've not found an explanation yet.

In the foreground of the pic and a little more to the right, in front of the bookcase is where it cupped last year during the coldest part of the winter. When I see a forecast on the news of bitter cold for a prolonged time I know that the cupping is coming. It seems like that should mean something, just dont know what.

Thanks for playing

JamesTRD,

If your theory is correct do you suppose there will come a time when all the wood will come to a stasis point, a point where the moisture level/content is evenly enough distributed that this might no longer be a problem?

And if your theory is correct does increasing the Rh in my home help or hurt the situation?

Ken Fisher,

I hope you didnt take my "thanks for playing" wrongly, it wasnt meant maliciously. Believe me when I say I appreciate any and all thoughts on the subject.
Its remarkable to me that this always happens in one location, not sure why, but man is it frustrating. If I ever get a chance for a do-over I'm going with stained concrete.

Wood only cups like that because it is wetter on the bottom than the top. Something is definetly going on in that spot.

You need someone with a non-invasive meter to check the moisture content of the wood, first in a non-affected area and then in the affected area. There should be a large difference between the two.

Just because a guy came out and put some nails into it with a antiquated meter and says it is in the normal range means nothing.

No problem rocks:

I'm lost on the cause but Perry's (Floorguy) comments are pretty much what I would have said initially, especially water/moisture finding the lowest spot on the slab. Something is creating moisture during the winter months and the source doesn't have to be where the problem is.