3 years ago, I had 5/16", oak hardwood floors installed on new contruction part of a remodel. The house is above a 24" crawlspace. Each of the last three years, the floors have become uneven. A slight lip between the boards appeared on some areas of the floor. On 700 sq. feet, there are about 75 spots where this has happened. The installer shaved down the uneven spots and that was fine for about a year...then, it happened again.

My question is...Is this cupping and is it caused by moisture. The description of "cupping" that I've read on this board, do not describe it like what I am seeing.

We took a moisture reading in the crawlspace and it was 17%. If the problem is caused by moisture, then I assume I should install a vapor barrier. If I do that, will the boards shrink only to leave gaps between each of the boards?

Thanks for you help. Let me know if I should clarify.