Hi. I'm new here and hoping y'all can give me some thoughts.

We had water damage in our home and as a result have had to replace the floors in literally every room but one. Ranch style home. Decided to go with hardwood. Upon ripping up the laminate and carpets, we found 3/4" particle board overlaying a 1/2" plywood subfloor (over crawlspace).

We removed the particle board and replaced with 3/4" plywood, so now we have 1 1/4" of plywood over the crawl space, with 3/4" unfinished solid white oak flooring over that. Planks are 4" wide.

Hardwood was delivered in Dec and installed in Feb and March so it had a long time to acclimate in the home. Wood was nailed, not glued or stapled.

I don't remember the exact numbers but we installed the wood when the subfloor and hardwood were within 2-3% humidity of each other.

Floors finished by hand and Rubio Monocoat applied. No poly.

Now that Spring is here and we're in the rainy season (We live in Alabama so it's humid here all the time; even in the winter), we are noticing ever so slight cupping on the floors in two rooms. It isn't obvious to the eye but can be felt slightly under bare feet. Our expansion gaps haven't decreased in size any, yet there is this ever so slight cupping.

Some places I read say this can be trouble and others say this is completely normal in humid climates if it's minor.

Thoughts, anyone?

Cupping all year is not the best for a hardwood floor. Seasonal cupping may be minimized by your heating and cooling system. It would take a lot of moisture to affect the expansion gap at the walls, like a flooded floor. It sounds like your floor is not having a problem that should be solved by a refinishing with sanding to bare wood and starting over. With the penetrating oil finishes there is not as much of a shine to the surface, so it doesn't show as much, even though you can feel it when walking in bare feet. Your regular maintenance coat should protect the wood from wear that will take place on the raised edges from traffic.

What goes on in the crawl space? Cupping occurs when the humidity level below the floor (crawl space) is higher than the humidity level in the living area. Are you able to control the relative humidity in the crawl space?