Hoping for any advice here. I would like to add a mudroom addition to our house that would extend out into our 2 1/2 car garage. I'm wondering if this is going to cause problems shifting the walls due to the fact that the addition would be built into the garage on the slab. The house was built in 1987 but in Wisconsin we have some cold winter and wonder how much the garage slab actually moves. Any advice would be appreciated.

Thanks

The movement one might expect here would be from frost heave, and if you had it, you'd know it. If the garage has perimeter foundation walls that extend to below frost depth, they probably protect the slab from ground water which could cause frost heave.

I see no reason why minor non-load-bearing partitions should not be built on the garage slab.