Polyurethane pulling away from floor

Q: We refinished our floors in September and they came out pretty nice. However, it is now January and all around the floor you can start to see separation between the polyurethane and each plank joint. Basically, the polyurethane is pulling away from the floor where each plank meets.

Again, the finish is not pulling away anywhere but at each plank seam and only slightly. What could be causing this? Is there anything we can do about it?

A: It sounds to me as if your floors have shrunk a bit during the heating season. If it is very dry in your house you may need to ad a humidifier in winter. I would try to keep it between 36-42% in winter. If you have it much higher than that, you will likely end up with condensation problems. An inexpensive digital hygrometer can be purchased from an electronics store, which, if you set it on the floor for half an hour or less will tell you exactly how dry it is at floor level.