I had 3 1/4" oak flooring installed in new construction in June 05'.Within days a waving appeared throughout . This job had been subbed out by a reputable flooring company. The owner at first didn't agree with what I saw. Sanding problems and coating over dirt. He checked the basement visually. No moisture ( dehu running). He didn't understand the cause. He sent out another group to strip , sand and recoat with 3 coats of poly. The man in charge of these subs said I would always have a problem just wait. He said alot of floors wider than 3" do this. They resanded in many spots against the grain. There is also a black mark running accross several boards( another person said a belt on the sander must have broken and noone cleaned the mark) it now has poly over it.Well so far the floors aren't waving. Just bad sanding, bad poly around doorways and the boards are seperating. Everyday I see more gaps in between various boards. I do not want to fill the large spaces with wood filler. I have already had these floors redone once. How many times can a floor be resanded.Please help!

Your floor had a moisture related problem, thats why they cupped ,too much humidity/moisture after the floor was installed. Now you are seeing the effects of it, most likely your floor will close up to some degree once you introduce some moisture back in the enviroment i doubt it will fully close but its hard to say. Bad sanding and covering over dirt I guess you understand there is no easy quick fix for that. I would just let it ride for a few more months and see if it closes up. IN the future try to keep the house around 45% rh yearround if possible this will reduce the seasonal movement you are seeing.

New construction, says it all. They rarely have the home completely sealed and the HVAC running for weeks to dry out all the building "wet trades", before the wood is brought straight in and installed, because if they acclimate it, it will grow legs!!!

Install a floor with high MC, and then come in and turn the heater on. The boards will cup. The gapping is the result of further loss of MC, from installation.

Don't be surprised when the boards "crown" (the opposite of cupping), because it was sanded.

This was a case of "we lost money so hurry up to fix it". That's why you have the finish problems now. They sent the cheap guy in to fix it, so they wouldn't lose more money from the price of a craftsman, with knowledge.