Back in early 2009 I remodeled three rooms and a long hallway of my house. I hired a flooring company to glue down over a 1,000 square feet of Dansk fusion (strand) bamboo flooring in my home. They used Bostik Vapor Barrier MVP4 and Bostik’s Best Adhesive to secure the flooring down. Within a week's time my centrally located water heater broke sending water under the flooring. I immediately called my home owners insurance carrier. They arranged to… have all of the new flooring ripped out, have a remedial water damage company come and remove all the affected wet dry wall, to place dehumidifiers throughout the affected areas and over a few weeks time completely dry out the house. I then called back the flooring company who checked the foundation with moisture meters and with strategically placed calcium chloride tests. They concluded that the flooring was indeed well under Bostik’s moisture content parameters with this type of application and that I could go ahead with a new install. I hired a leak detection company just for good measure to check the whole house and they did not detect any leaks anywhere. After hiring a handyman to repair all of the drywall, I painted all of the affected areas (actually repainted all of the walls of the rooms for a clean even look). Still worried about potential future leaks, I hired a plumbing company to reroute all of my plumbing into the attic (plumbing was originally under the foundation). I even installed an on demand water heated in another part of the house (to replace the one that had failed) and removed an outside planter box from away from the exterior of the house. I really did not want to repeat any kind of water damage incident to my flooring.
However, within weeks of the new installation the flooring began to cup throughout all the rooms involved. I am perplexed at what would cause this. I inquired with Dansk before that second install about the Bostik system proposed (same as the initial install). They assured me that it was an acceptable system. I'm not sure what can be done short of ripping out the flooring once again and that is not a pleasant thought.

Thats the kinda situation where I would perform an Rh test (along with the CaCl) using the Wagner Rapid Rh probes to check not only the current rh but the drydown. Concrete accepts new water way faster than it can evaporate it. We're talking up to several months, not weeks.

Not sufficient acclimation time, to gain the moisture it gained after installation was completed, from normal humidity levels in your residence.

Given the moisture barrier was applied correctly and at the correct thickness to begin with.

A gradient test will tell the truth. Top to the bottom of the plank, is moisture content consistent, or does it gain MC at the bottom of the plank?

I agree with Perry.
You may be wise in hiring an inspector.
On this job, make sure the inspector understands board set measurements as bamboo is a grass. Bamboo has so much glue/resins, moisture testing may not be of help as the meters may be reading the glue or resins.

I agree with SP.
In this situation the appropriate testing would have told them that the substrate did not have adequate drying time. The Bamboo could have acclimated to the room environment for a long period of time, and still may not have been suitable to install on a substrate in this condition. As we all know...Moisture barriers reduce moisture.

As mentioned, cupping is indicative of moisture from below trying to escape upwards through the flooring. Rarely, a cupped floor will correct itself so 95% of the time sanding/ refinishing or full replacement is the only course of action.

Thank you to all who have responded.

I suspect that the foundation is just too moist for this sort of application. It was at least three months before the bamboo was reapplied and there was no other source of water under the foundation other than what naturally comes up from the earth. I didn't even water the grass for at least six months as we were having a water shortage here in sunny Southern California and were asked to cut down water usage by the water company.

The bamboo cupped within a few weeks of application including areas where there was no original water damage from the water heater (different room entirely).

I am surprised that the soil would be so moist under my home as to cause this -if- this product is indeed a good one. Others in my neighborhood have engineered hard wood floors so I figure that -bamboo- is not the best choice on a slab foundation. Too bad as it's quite beautiful looking straight down on it (just don't look across it as the light reveals the severe cupping). It is also too bad that the flooring store pushed so hard to get me to redo the bamboo and ASAP. They would have redone it within a few week's time but I delayed. I was assured by them that the floor was dry enough especially after three months (calcium carbonate tests and their Wagner probe meters showed it - I watched them use these meters and readings were acceptable per their specifications). They would tell you that I was very resistant to redoing the floor as I was pretty freaked out about having just laid it only to have to rip it up the first go around. I wanted to make sure that there was no water source to damage a future installation. It's also too bad that the flooring store either doesn't really know this product or perhaps don't know enough about slab testing.

Even with an inspector looking at my flooring I can't imagine how this situation can be corrected other than ripping out the bamboo again and replacing it with a more suitable product. You apparently can not sand Dansk strand bamboo. I don't guess there is a magical way to dry out permanently one's slab while it covered with a glue down product --- unless there is an underground spring under the house that I don't know about and I can reroute it to another area of my yard where the water would be more appreciated .

I'm thinking using tile next time round or using a plastic barrier with a floating floor and not a water barrier/glue down system. That way if there are problems, I can take up the floor a bit easier.

How can you possibly come to any sort of conclusion concerning this failure without the needed tests and data?

Perry was correct in his suggestions which is to perform moisture testing from the top to the bottom, measure board sets to determine size upon installation.

If cupping is due to concrete moisture, there may be a vapor barrier failure.
If the cupping is due to lack of acclimation, then the failure is not due to excessive concrete moisture..

An inspector can give you the data needed to determine cause of failure. All anybody on a message board can do is give you various situations by which cupping can occur.

Cupping can occur due to a moisture Imbalance.
Raised edges occurs when the material swells and has no place to go so the edges raise giving a cupped appearance. The material swells because it gains moisture after installation.

Did you open the boxes and remove the plastic to allow the material to acclimate to your climate??

Hi Ray,

The installers really didn't acclimate the flooring before installing it. I asked them about that, because I had read on-line about acclimating regular hardwood by opening the boxes and letting them sit inside the area of installation for a few days at least, and their response was that with this product it wasn't necessary. I even called Dansk in Canada and they said the same thing. I was quite surprised. Again, the flooring store was quite insistent to go ahead with the project so we did.

My house was done in two sections so that I could stay in the house during the installation process. Each was the same pattern. The boxes were set down inside my garage while they troweled down the Bostik Vapor Barrier. Then the next day they brought in the boxes and installed the planks using the Bostik Adhesive. I stayed off the floor for 24 hours after it was installed.

I could have an inspection of the flooring but the end results will be that I'll have to remove the flooring anyway. It would answer perhaps who or what failed or didn't fail. At this point, true enough, I don't trust the Dansk, Bostik, or my flooring store. I only know that the areas in the house that are tiled have no issue at all with moisture.

I'll probably end up having an inspection for documentation sake.

Hi StillLearning. Just checking on your thead. I should have a couple numbers for you to call by tomorrow afternoon after I contact the people who can help you.

Thanks for calling, was a pleasure talking to you.

Cupping is one thing, edge compression is totally different.

The concern is also where there was no water damage........

When A board is not acclimated to gain the moisture it is going to gain after installation and those boards are installed tight and bonded well. The individual boards swell, expand. Your not going to keep it from expanding. The edges of the boards compress against each other and you get a raised edge, that resembles cupping.


I can look at a wood floor that is cupped and tell right away if it a moisture gradient, or a compression issue. The wider the board, the easier it is.

Yea, installing out of the garage is never a great idea either. They failed in that respect to even bring it in the house to sit...temp and rh wise.

Then came to find out the CaCl test was not performed correctly by the salesman either. Reciepe for a disaster. And whats with these bamboo manufacturers saying that it is ok to test the concrete with a concrete meter? Even Teragren says that as well.

If Dansk said you did not have to acclimate then whats this about on their site?

http://www.danskhardwood.com/download/t ... 022010.pdf

Dansk Preparation Checklist
Ambient Environment
Bamboo Fusion flooring must be acclimated
and installed in controlled environments with
a stable temperature of 15 - 24 C (65 - 75 F),
with an internal ambient relative humidity
level between 35% - 55%

It is interesting that you found that data on the Dansk site. I'll have to check when that was included on their website. If it was posted years ago than I would say that my flooring store should have known all of this. I'm not sure why the Dansk contact told to me that it was OK to go with the flooring store’s assessment to skip the acclimation if they were convinced that it was necessary back then for all cases. The floor store claimed that they had installed this product many times here in sunny Southern California.

I'm trying to remember what I was told. They may have been thinking the following....

If the boards were allowed to acclimate to the relatively low levels of humidity in the ambient air of my home, they then would contract. If then they were installed over a system that would provide additional moisture, they would expand even more over time than if they were not acclimated at all. The higher humidity during production of the boards should better match the moisture produced by the Bostik system. The boards would be better off staying at the higher humidity of production.

... Does this sound feasible?

S.P.
After talking with you, I'm thinking that it is more likely a case of "dry cupping." Correct me if I have this concept wrong... It occurs when the upper side of the boards (dry ambient air side of the room) is much drying than the under side of the boards (glue down side). Even when there is not an excessive amount of moisture on the foundation side, there is a significant moisture differential (upper side vs lower) causes the board cupping. I also have the impression that that I should purchase a meter and watch the relative humidity and temperature of my house keeping it at a level that best suits the flooring. Might this lessen the effect of current floor cupping or is this simply for future reference for new flooring?

are there gaps between the boards or are they tight together?

StillLearning, there's no way to tell what the conditions at the time of installation were in your house verses in the garage. Thats why the manufacturers always say to acclimate to conditions in the house...not the garage. And even some go as far as saying acclimate in the room to be installed. Not sure what the weather was like then but the garage could have been easily ten to twenty degrees hotter or colder than the inside of the house. Not to mention the rh. And note the manufacturers rh requirements, if you get a humidifier prior to installation and accilamation then bring in the wood...check the MC of the flooring to see if it jives with the interior temp and rh you can start installation, By all means get a thermohygrometer like I mentioned at RadioShack.

This is why contractors or stores with contractors licenses should always document this. But people get in a hurry to make a buck. The installers were just doing what they were told I am sure. Bet this one is chalked up the bad installation like many inspectors say....90% of all flooring faliures are installation related.

Your definition of dry cupping is correct. But needs to be determiined by your inspector. Have you guys gotten together yet?