Humidity from below or bad milling / installation causing overwood? 1 Answer

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Can humidity in subfloor cause overwood? Or is it installation issues?

Q: Can humidity in subfloor cause overwood? Or is it installation issues? I have several examples in my newly installed floor, plus several cracked boards. Some of the tongues at install were observed to be severely fractured, with multiple staples piled on top of each other. Also, the incorrect fasteners may have been used.

The contractor is blaming subfloor/basement humidity (floor is on first level above the basement), but I think it is a bad installation.

A: Moisture in the air or from any source that is too much for the wooden floor to transfer through and out of itself will cause boards to expand, generally side to side. This puts all the boards under pressure and you will get some cupping and raising of board edges. In severe cases the floor will heave upward. This pertains to flat sawn wood. Quartered and rift sawn can also expand up and down.

Has anyone pulled out a moisture meter to take some readings?

Follow-up Q: Yes, flooring rep and distributor came to site with contractor.  Took readings of subfloor and joists.  Also measured spacing of fasteners I think – used a magnet?

I have not seen any of those results however. The contractor did share a claim denial letter from flooring manufacturer (distributor filed claim against MFG) that was very general in nature, stating that cupping is never a MFG issue, always a site issue.  But it does not state what the site conditions that they measured were.

I don’t think it is cupping – each individual plank appears to be fine, it is their height relative to each other.  And problem was noted within 2 weeks (I am guessing it was there since install, but it was covered with cardboard for 2 weeks due to other work still going on.) Time frame was late May through early June, with only a couple of humid days in that period.

(Picture included.)

A: That is a nasty looking picture.  From that angle, it appears that you have quite a bit of gapping from one board to the next.  This can happen
if the environment, sub floor, etc. are still holding significant moisture, which can be the case with new construction. In such a case, the hardwood will expand, pushing adjacent boards over.  When it starts
to stabilize and shrink, you are left with the gaps. 

Having said that, one of the main reasons factory finished floors have a beveled edge is to hide the height difference from one board to the next.  If the tongue and groove milling is not great, sloppy, etc., you will end up with an uneven floor.

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