6” wife 3/4” white oak, “euro style”. Just finished installing on the first floor with nails and glue, moisture of flooring and OSB subfloor were both at 6%. Room humidity has been 30%, within a few points. Acclimated in the house for about a month.
What I just noticed is slight cupping. Maybe 1/16” at most, but consistently across the whole floor. Is this normal after bashing the flooring together? After sanding, will I have a problem? Could the glue provide the moisture on the bottom to cause this? Doubtful. I haven’t seen any moisture change in the floor or the air much. We’ve been living in the basement, also haven’t seen moisture swings.
Should I worry?
Thanks, matt

Just saw that water is the first ingredient on the glue I used.

Can you clarify a few details - it sounds like you have engineered hardwood given the wide planks, I'm also not sure why you used nails and glue, instead of just one or the other. I always push glue for engineered wide plank, and the water/moisture in the glue is never an issue for the flooring (provided you have the correct glue - polyurethane > water based for long wide boards in my experience, water based glue cleans up easier though)

Based on what you've outlined, if your RH sat at 30% for the month that wood acclimated, then you would have definitely installed it too dry. RH should be between 35%-55% ideally for installs, and throughout the year. If the wood went in dry and picked up excess moisture from a cheap, water based glue, then it is possible it expanded beyond the gaps left around the perimeter (you did leave expansion gaps, yes?) and cupped as a result.

As an aside, this is a good example of why acclimating the wood isn't always the right move - if the site conditions are going to be too dry or too humid at the time of install then acclimating the wood to these conditions will lead to failure 6 months later when the seasons change. We keep our warehouse at 45-50% RH year round so that installers can pick up and install the same day. If the house is too dry in the winter, then the wood might gap after install, but eventually evens out and is much better then installing dry and having it expand and buckle 3-4 months later.

One final note - don't sand a cupped floor. It will crown when the MC returns to normal, and then you are stuck.

Could be manufacturing as well. I said could. Noticeable before the floor was installed?

Some boards have this before install, but the rate on the floor, installed is much higher.

Yes the glue that has water will make it cup but should go back down in a few days.