You should proceed by finding an NWFA certified inspector in your area and paying him to do an inspection. Unless you know the moisture level in the air and wood, and things like nailing schedule, any opinion on what's wrong or how to remedy is strictly a wild guess.

Hi brickeyee, you wrote that "winter installed floors are not laid all that tight" Are you saying that professional installers (meaning installers worthy of the word "professional"), would know not to lay the boards tight in the winter and allow for summer expansion? I'm asking because my kitchen floor is experiencing cupping similar to the original poster's description. I'm in MA, and our kitchen wood floor (3/4" Somerset hardwood, tongue and groove) was installed at the end of January. The wood itself had been sitting in a room adjacent to the kitchen for a month prior to installation. The installers definitely put the boards in tight at that time (I could see that). Now in the summer, with weeks of humid weather, the floor boards are cupping. No buckling, but I am wondering about the long term consequences, as I simply have no knowledge of this area. The basement is humid at this time of year, but none of the 100 year old floor boards in the other rooms over the basement are cupping. Yes, they do have slight gaps between the boards--that is part of their character. But only the new flooring in the kitchen is cupping. Should the installers have known not to install the boards so tight together in January? They are local residents of MA, so they know it gets humid in the summer. And (of course) no one asked me whether I wanted the boards to go in tight, and would I have minded if there were gaps to allow for summertime expansion. Thanks! Lee

The pictures I showed are from the second floor, not over the crawlspace. I have similar issues on the first floor that is over the crawlspace but they are no worse then the second floor issues. So I don't think it's an issue with humidity from the crawlspace, at least on the second floor. One thing that is puzzling to me is that the sag shown in the pictures is around 5' from peak to peak. That is more then just sagging between the trusses. And it's a lot worse on then side of the hall where the picture is taken then just 3' away on the opposite wall. There is still some sag along the opposite wall but not near as bad as what is shown. I do have a section of flooring that goes from one side of the house to the other. It's around 49' long. It's around 30' wide in some places and as narrow as 8' for around 20' of the 49' The floor runs perpendicular to the 49' length which also makes them run parallel to the floor joists. Is there any benefit to running the floor perpendicular to the long run that would cause them to do that over running them perpendicular to the joists?

The shape of the wood will tell you the direction the moisture is coming from. The planks are cupping (edges of the planks are HIGHER than the centers). If you can image the plank is shaped like an arrow head, the "point" will tell you where to look. Cupping boards tell us (visually) that the BOTTOM of the floors are WETTER than the top. The arrow head is pointing "down" (I hope I'm saying that right). So...crawlspace. They can be the DEATH of wood floors if done poorly. And you've already discovered that the builder likes to cut corners. And anything that is "out of sight" would be considered "out of mind" by this guy. Photos of the craw space and humidity readings of the area will be the biggest place to look. And an NWFA Certified Inspector is worth his/her weight in GOLD when it comes to new builds. Their reports hold up in court and they can help you get a new floor should this one be beyond salvaging.