Black discolorations in tongue and groove

Q: I professionally installed a engineered maple floor on cement slab, which was tested for moisture before laying. The floor showed no signs of green or dark wood in the tongue and groove. Six month later I pulled down from my attic, (no leaks) my 2 open left over planks and 2 new boxes of maple flooring wrapped in it’s original plastic to repair 15 spots throughout my home that have black discolorations. The old and new flooring was very black in the tongue and groove.

I was ready to repair once I determined there were no leaks in pipes and in sewer. I believe the material was faulty. What ever the black is, it did not show when it was newly installed. My question, what kind of growth could this be ? Like what types of things are known to growth on maple flooring in the industry? Do labs that test for asbestos, test things growing on wood? I need a new floor.


2nd question re: Black Iron Oxide. That is what it looks like on my stored flooring. Does this ever happen, the power tools to shave and sand the maple for engineered flooring left microscopic metal shaving in the tongue and groove?

My floor was glued, no metal touched it. I used a Bissell wet vacuum 2 times and I think water got into the tongue and groove area. Shortly after, there was my first discoloration, which is now 15 places thru out my house.


A: There was no problem with the flooring when it was delivered and it took 6 months for this issue to appear?  That to me sounds like the problem originates in your house.  Maybe it is black mold.  It is really not a good idea to use a machine for maintenance on wood which dispenses water. 

You could contact the manufacturer and ask for their input. 

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