Buckling engineered oak floor... 6 months later

We had our house refurbished and part of this included filling the floor with concrete and then laying an engineered oak floor above it. The floor is mostly fine, though there is one area in the hallway where the floor is buckling - not a lot but the door into the hall opens over it, hence we have noticed.

Is it normal for floors to buckle so much later? What could possibly cause this?

 

How soon was the wood laid over the concrete?

 

Any moisture tests made before it went down?

 

It was about 8 weeks and the moisture content was around 5%. I also did the test of putting down a plastic over the sub floor and no moisture was noted prior to installation.

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Im assuming you are aware of the expansion allowance when installed?
Buckling in my experience has always been down to mainly moisture but have seen a lot fitted without the expansion taken into consideration

 

Acclimatised?

 

Yes, quite sufficient (1 inch total) and the floors were acclimatized for 3 weeks.

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Has it raised a lot?

 

Probably about 5mm,but because of the door opening the very it's most inconvenient!

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