New Hardwood flooring Cupping and Buckling

audsquadJuly 17, 2007

We had hardwood floors installed in our new home in January. The floors sat in the house for over a week before being installed.

The floors are 3/8" Durawood Stained Brazilian Oak from LL.

Now that the summer is here and the humidity has gone up, we are noticing a significant amount of cupping, and in a few places the floors have started to buckle (the floor has formed lumps) and in two spots (in the DR and LR) the floor has actually popped up and is no longer attached to the subfloor.

We called our flooring guy (who lives down the street), and he said to run a dehumidifier in the basement and all will be fixed.

Dehumidifier has been running for a week, and the RH downstairs is at 70%, and upstairs is at 53%. We do not run AC because the house rarely goes over 75 degrees. I know the floors will not dry out overnight...but they don't seem to have gotten any better- maybe even worse.

The house is a cape style, unfinished attic (but insulated), unfinished basement.

I know some of the moisture is due to the lack of gutters (which we installed this week...finally!), inadequate attic ventilation (need to vent the bath exhausts through the roof which will be completed shortly), and the basement ceiling insulation has not been installed yet (Will be completed soon).

I live in Massachusetts- where it gets hot and humid inthe summer.

My questions are....

Is it OK to install the R-19 insulation- vapor barrier on the ceiling in the basement- now? While the RH level is still hovering just below 70% in the basement? Dehumidifier is removing approximatley 50 pints/day. If the subfloor is moist will the insulation "trap" the moisture there?

Should I run a dehumidifier on the main living floor where the RH is 53% Or, should I run an A/C (we have a window unit? Or is neither necessary?

Will my floors recover?

Should I insist the floor guy come and fix the issue? Or wait until the fall when the floors dry out? (If they do)

In some places there is a space still between the floorborad and the wall, but in other spaces it is pushing against it. I think the floors were installed in the winter when the RH was low and he didn't account for it by allowing adequate apacing between floor boards. HE claims it is all due to the moisture level in the basement. I think maybe the cupping will get better, but the buckled floorboards will not. Who is right?

Other than the cupping/buckling- the floor boards look OK.

Next summer...with my gutters working and diverting water, and the insulation installed with the vapor barrier, and a dehumidifier in the basement - will I have to be worried about my floors lifting again?

Anyone with any advice/wisdom/similar experiences???

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Wow, I am sorry about your floors. I would suggest running the A/C with the dehumidifiers until the issue is resolved, then develop a system to maintain a consistent humidity level in your home.

People often forget that one of the main functions of A/C in addition to cooling, is to dry out the air. Maintaining a more consistent year-around humidity level in the home is better for furniture and the home's building materials.

That said, your flooring guy should have allowed sufficient room for normal expansion/contraction to prevent buckling. I hope you get this issue resolved quickly so that you can enjoy your beautiful floors.

    Bookmark   July 17, 2007 at 3:45PM
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Cupping is usually the result of a moisture issue underneath the flooring, not always, but in most cases.

How high did the RH get upstairs?

The homeowner is responsible for maintaining an acceptable RH either by the running AC or a dehumidifier. Your installer is responsible for leaving adequate expansion space.

    Bookmark   July 17, 2007 at 5:49PM
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Jerry-T. I am not so concerned about the cupping as I am about the buckling.

Is the cupping caused by the moisture and the buckling by the lack of expansion space?

cass62- I do not know what the humidity level was in the house- I will say there was only one day where I felt "sticky", the house is 2x6 construction and maintains a temperature that we feel is comfortable without an A/C...however I think now I will run one for at least a couple hours a day to remove moisture in the air.

Is 70% RH acceptable for a basement? Is 50% RH acceptable mor the main floor?

    Bookmark   July 18, 2007 at 7:54AM
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One more thing- I reread my original post...and I shouldn't have said "severely" cupping. I actually didn't even notice that they were cupping until the installer mentioned it. I would classify it as "slightly" cupping- unless the light is hitting them at the right angle, it's not that obvious. However, the buckling and heaving is very obvious!

    Bookmark   July 18, 2007 at 8:54AM
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I'm seeing 2 issues here.

Yes, the basement is real high in humidity, and will cause the underside of the substrate to have a higher moisture content then the flooring, causing cupping. Your floor guy should have know this, as it is a very common and known problem.

Second, is the fact the wood was acclimated and installed during the winter, and the heating season, when running the heat in the home, has lowered the humidity. How much??? The wood was installed at that low moisture content, and now that the humidity has risen, so has the moisture content of the wood, swelling it, and causing a buckled floor and not just cupped.

But you said everything was fine, till summer. This leads me to believe no control gaps were left in the dry floor to accomidate the swell that was going to happen and now has happened(species shrink & swell coffecient). Edge crush from a swelling floor will have a cupped appearence.

I see both rearing their ugly heads at the same time.

    Bookmark   July 18, 2007 at 11:54PM
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Thanks floorguy. The only room where I see NO issues whatsoever (cupping or buckling) is in my small office where the expansion gap left was almost an inch. This is why I believe the floor guy is at fault, and I can use this room as an example.

He told me something like "the buckling is happening inthe middle because the floors have no where to go- the wall gap is irrelevant". I smell something fishy.

    Bookmark   July 19, 2007 at 7:46AM
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when I was with Bruce they showed us a picture of a gym floor that literally buckled and you could walk under it. Wood expands width wise not length wise so if there is no gaps left width wise that is most likely your problem

    Bookmark   July 20, 2007 at 9:01PM
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You can't compare a house to a gym floor. It is quite possible for a floor to move... and see the effects out in the field first. It depends on what the substrate is, how well it was fastened down and the width of the room. The boards want to move and have no where to go but up on the edges, slight cupping, compression set. It can also start to buckle out in the field without taking up all of the allowed expansion space.

I would like to see some photos before I place "all" the blame on the installer. Homeowners have an obligation too for maintaining a proper environment for wood flooring.

    Bookmark   July 21, 2007 at 5:41AM
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Floor guy came by, saw floors - said "OH MY GOD". He believes the floors are defective and it is not our fault. When he saw them the first time it was well over a month ago, when they were slightly cupped but not buckled. He is going to call manufacturer and see if there is an issue with the lot the floors came from (luckily we still had one box!). If it is not defective floors, then he is just going to have to relay them...

    Bookmark   July 26, 2007 at 8:06AM
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I'll bet money, that there is nothing wrong with the flooring, that would cause buckling.

It is wood and it is doing what wood does. It swells with a gain of moisture content, which your has, and it shrinks with a loss of moisture content. The floor has gained moisture since it was installed... FACT

The floor was installed drier, and now it is wetter.

    Bookmark   July 26, 2007 at 10:34PM
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floorguy- that is my thought. I think it was a faulty installation. I am just glad he is going to fix them.

    Bookmark   July 27, 2007 at 2:24PM
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I just had a premonition. Your floor guy is going to lay new wood for you. Then in February you'll be posting about huge gaps all over. Not that the installer didn't screw up, but you also really need to get your humidity under control and/or consider using an engineered wood.

    Bookmark   July 30, 2007 at 5:04PM
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I install wood floors from time to time and one thing that strikes me in this post was there was no mention of a proper vapor barrier such as felt paper installed under the wood floor and on top of the sub floor.Humidity is going to rise from the basement regardless of what you do if you dont use felt paper under the flooring no matter how long you acclimate the wood prior to installation or how you adjust the humidty in the home your going to have a problem. Check with your installer alot of them know how to put wood together but dont know the right way to do it. One other thing that should be done if the floor runs width wise more than 20 feet it should be run in both directions from the middle by using spline. Also a 3/4 gap is prefferd on all the walls where the floor meets.I would personally not blame the home owner in this case.

    Bookmark   July 31, 2007 at 3:33PM
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Good point of the felt if the flooring was mechanically fastened down . But, saturated felt is only a retarder, not a true moisture barrier.

I hope my own posts are not placing the blame on anyone... too many variables are unknown.

    Bookmark   August 1, 2007 at 5:33AM
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The floor installer is now insisting that it is our problem, and wants an independant third party to come in and inspect the floors. Fine by me. He left 1/4" gap only. There is that pink paper under the floors (Rosin paper?). On one wall only, the floors have expanded all the way to the wall and are starting to buckle at the edge. On the other wall- no movement.

We'll just have to get a third party in here to make an educated decision on the floors.

    Bookmark   August 9, 2007 at 8:32AM
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Smart choice... I would recommend someone certified by the NWFA. Normally certification does not mean much to me... except for inspectors. Anyone can join the NWFA and "claim" to be a consultant/inspector. Only certified inspectors tell you they have taken and "passed" the NWFA training courses.

    Bookmark   August 10, 2007 at 5:27AM
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This is clearly from what is presented a moisture imbalance due to high humidity in the basement migrating upward into the subfloor and hardwood floor. A moisture meter with insulated pins will measure the moisture levels from the top to the bottom of the wood subfloor. If higher from bottom to top a clear indication of high humidity causing this condition. A vapor retarder is only usefull for retarding vapor and when penetrated by all the nails even less helpful for long periods of moisture.
It has been stated she doesn't run the AC so likely a greenhouse effect is also causing high levels of humidity in the upper levels. Find a NWFA Certified Inspector and have him identify what you can do regarding the above.
One can guess, from years of experience, what is causing this but only testing by NWFA standards will conclusively prove what the problem is and how to remediate it.

    Bookmark   August 7, 2012 at 11:27AM
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I commend you NWFACP, you timed that almost perfectly to be 5 years after the last post on this thread, and amazingly enough you did not register yesterday but 3 days ago!

    Bookmark   August 7, 2012 at 3:55PM
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Being new to this forum I neglected to see how long they leave postings up. Perhaps they feel others may benefit from this information at a later date. If not I guess I just wasted my time. Good to see someone noticed!

    Bookmark   August 7, 2012 at 5:01PM
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"no mention of a proper vapor barrier such as felt paper installed under the wood floor"

Nothing you can do is going to stop the wood from absorbing moisture and changing size.

It has 24 hours a day, every day, to come to equilibrium with the humidity it is exposed to.

Winter installed floors are not laid all that tight.

Summer floors should be tight.

No fastening is going to stop the movement, n finish is going to stop the movement.

The design of t&G strip flooring is so that only one edge is fastened in place anyway.
The the other edge is free to move as the wood swells and shrinks.
Gaps in the winter heating season, tight in the summer cooling season.
See Chapter 3 of the 'Wood Handbook' linked below.

Figure 3-3 is especially important to understand cupping, and the other changes in shape that occur with changes in moisture content.

Here is a link that might be useful: Wood Handbook, Chapter 3

    Bookmark   August 8, 2012 at 5:04PM
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Hi brickeyee, you wrote that "winter installed floors are not laid all that tight"

Are you saying that professional installers (meaning installers worthy of the word "professional"), would know not to lay the boards tight in the winter and allow for summer expansion?

I'm asking because my kitchen floor is experiencing cupping similar to the original poster's description. I'm in MA, and our kitchen wood floor (3/4" Somerset hardwood, tongue and groove) was installed at the end of January. The wood itself had been sitting in a room adjacent to the kitchen for a month prior to installation. The installers definitely put the boards in tight at that time (I could see that).

Now in the summer, with weeks of humid weather, the floor boards are cupping. No buckling, but I am wondering about the long term consequences, as I simply have no knowledge of this area. The basement is humid at this time of year, but none of the 100 year old floor boards in the other rooms over the basement are cupping. Yes, they do have slight gaps between the boards--that is part of their character. But only the new flooring in the kitchen is cupping.

Should the installers have known not to install the boards so tight together in January? They are local residents of MA, so they know it gets humid in the summer. And (of course) no one asked me whether I wanted the boards to go in tight, and would I have minded if there were gaps to allow for summertime expansion.


    Bookmark   August 18, 2012 at 1:24PM
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"Are you saying that professional installers (meaning installers worthy of the word "professional"), would know not to lay the boards tight in the winter and allow for summer expansion? "


It may not be much since a strip floor has ever single joint to expand over, but even a few thousandths of an inch per strip racks up pretty good over 20-30 strips of wood.

It is sort of the difference between hammering them as tight as you can and just bumping them once.

    Bookmark   August 20, 2012 at 2:53PM
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Hi brickeyee, thanks for responding to my question!

even a few thousandths of an inch per strip racks up pretty good over 20-30 strips of wood.

What a great description -- I never would have thought of it that way until I read your posting. And it makes it so clear.

Thanks again! You are a huge help.

    Bookmark   August 20, 2012 at 10:00PM
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Lack of expansion joints cut on all sides of engineered flooring at the walls is a major cause of both problems. The picture attached (I hope) shows what I am working on right now. The quarter round and trim board was removed for access to inspect and repair. I have no cupping but there are multiple bucklings of butt joints on the same run of flooring. The ends of the flooring cannot expand outwards with temperature or humididity changes. Notice that some gap was cut and little if any properly cut next to it. Same goes for the the rest of this flooring installation. I would have to think cupping is the same problem - not enough expansion joint cut on the sides of the flooring. Now for the REST OF THE STORY! This type flooring is suppose to float. It is not to be tied to the sub floor in any way. It is supposed to have a vapor barrier pad. none of the flooring should be glued or nailed together or anyway whatsoever nailed to the sub floor, wall or anywhere else.
The installer of my floor child problem used a long brad gun to install quarter round but, shot brads through the flooring into the sub floor - thus locking the flooring in place and guaranteed buckling. The quarter round should have been nailed horizontally to the trim board. You may be able to zoom in on flooring pix and see nail holes. I have to locate any that may be broken off and remove them. One missed brad can can cause a later nightmare. Get them gone now. LOL and next time - do it correctly.

    Bookmark   November 11, 2012 at 9:13PM
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