Hardwood floor about 40 years old buckled with no visible reason. No rot, damp or mold under the house. A mystery but a dangerous trip hazard.
Start tearing it out, preserving all we can to re-use it. Still not good reason for the buckle.
Aha… though dry now, it appears the subfloor was wet sometime in the past. Being under a new air conditioner the likely culprit is an old window unit that was mis-positioned and drained inside rather than outside and as the wood got wet it swelled, putting pressure on it’s abutting mates until a couple of them gave up and stood up in protest.
Remove all the old subfloor until reach good wood with no visible evidence of past water infiltration. Thankfully the joists are solid and have not rot.
Install new sub floor
Put felt paper vapor over subfloor and begin re-laying the salvaged hardwood
Couldn’t salvage all of it but will try a clear oak floor and stain to match as close as we can.
The stain isn’t perfect but it’s close.
Sand and apply a lacquer to the entire floor, sand again, repeat and add the final coat. Looks good…a different perspective might give a better look at the finished job but if Mountain was a professional photographer he wouldn’t be such a good carpenter.