We recently sanded an old oak floor thoroughly and then applied 6 coats of a water based varathane over it. The result was beautiful but now we are experiencing cracking with loud noises in the joints. Some joints have opened slightly and the floor is no longer as smooth as it was. Did humidity cause this problem and how can it be remedied?

WOW! Six coats of water based? How long did you wait between coats? Were you able to get them all on in one day? What exactly is the brand of finish, what did you apply it with, where are you located? WOW!

We used Flecto Varathane Diamond Wood Finish in Satin. We waited approximately 5 - 6 hours between each coat and applied the coats over a three day period. We used the recommended applicator. We live in Toronto in Canada. The temperature at the time was 15 degrees Celsius, three degrees higher than needed.

So much for my theory. I was thinking it was applied too heavy, without enough time to dry between coats. Sounds like it's panelizing, but I have no idea about the climate up there, guessing cold and dry inside. Any idea what the humidty inside your home is?

Waterborne finish have very strong adhesion properties thats why many now call for some type of sealer underneth. It's possible sections of your floor are "glued" together on the sides. As your floor starts to shrink they are breaking that bond between the sides of the boards. You can keep the floor movement down by keeping a constant rh in your home. Idealy it should be close to 40 to 45%

Noises at the joints is the bothersome statement. Noise indicates excessive movement. The movement may be causing the surface cracking, if the cracking begins at the joints.