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Flooring and Carpeting/Bamboo flooring separation


I recently had a new home built. The entire first floor was done with bamboo flooring. The flooring was installed in July 2013. Starting around November I noticed some gaps appearing along the lengthwise portion of the boards. Since then the gaps have continued to widen. I can fit two quarters within the gap at the largest area. I read through some online forums that indicate the flooring will expand/contract with changing humidity levels; however, based on what I'm reading the gaps in my flooring seem excessively wide.

There is also a lot if deflection in the floor. There is a large island in the kitchen area that is covered by a quartz countertop. Items on the island will shake when someone walks by. Is it possible that this is the cause of the separation.

ANSWER: David,

sorry to reply so late...

Separation like that is unacceptable and complicated.  What is the sub floor made of?? If it is a OSB board that maybe the issue. Improper sub floors do not allow for a good nail purchase into the sub floor allowing the bamboo to move and expand or contract. Improper joist spacing can cause the deflection and the inherent flexing also weakens the nail purchase or holding strength. OSB (oriented strand board) is not an approved sub floor by the Flooring Association standards unless it is the proper thickness and possibly tongue and groove. See FYI below.
As the nail works loose so does the floor.
I am assuming it was installed over a wood sub floor... and it was a nail down this correct.
Other factors maybe the length of the nail or STAPLE ? Staples are used often and they are less expensive than a cleated wood floor nail.

The contractor is liable if he did not install the bamboo over the proper substrate / sub floor. The deflection alone tells me he should have added an additional layer of PLYWOOD to the first layer of sub floor to make sure the bamboo would be properly supported.

If the bamboo was glued down or is a floating floor please advise me.




---------- FOLLOW-UP ----------

QUESTION: Thanks for the reply. No problem with the time frame. I was mostly looking for reassurance that the degree of separation was not a consequence of normal expansion/contraction of the wood. I'm not sure the specifics of the subfloor. I do have pictures of the area just prior to installation and one pic of the area during. It appears to be a normal wooden subfloor. The boards nailed down to my understanding. The spacing of the joists is normal from what I'm able to gather through my reading of the topic. I just want to make sure I fully understand what could be wrong before I ask the contractor to correct the issue. The relationship has begun to unfortunately turn a little sour.

Do you think the weight of the countertop covering the island could cause the increased deflection and be the route cause of the boards moving?  The room is wide open and measures approximately 45' by 20'. There are no support columns in the unfinished basement. I was told they would not be necessary.


Sorry to say the images did not come through and I would like to see them. feel free to send them to

I am shocked that the area is not supported from beneath as you have indicated.

There is a rule called L360....when I get a chance I will link to you so you can read it yourself.

Basically it has to due with the unsupported span of joists...and what the floor can support when we want to attempt tile or stone installations. There are certain formulas we have to adhere so the floor will not out weigh the support of the in your case the floor sounds like it is not supported sufficiently.

You will do well to get city codes if any exist and talk to an inspector to see if the contractor followed code.

Tons of stuff out there, the first link has other links to the tile forum i have visited many times

Will be looking for those pics and feel free to question the tile forums as well...great guys and good problem solvers.


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20+ years flooring installation ...carpet,wood,tile and vinyl. Residential and commercial. I do not sell the products , just install what ever the shop / customer has purchased. I actually love seeing the finished project completed and it gives me great satisfaction to help others acheive that goal. If I don't know the answer I will say so, and then I will recommend another expert for you. I may even research the subject and answer to the best of my ability ...including links to my sources. I wish you all success Chris


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