The floor in the living room I had installed didn't meet the wall. There was a 3 inch gap left all around my livingroom floor. I could see under my home. It was then covered with luan and carpet. Why? Won't this cause future problems, mice etc.

What does your contract state?

Did you ask contractor why the space was left and the finish changed?

What type of floor was installed in the middle?

If space was larger, like 12'' or more, I would guess it would be a design feature.

If everything is fitted tight can not see any problem with mice.

Chuck