I have been looking at the NAHB guide for frost-protected shallow foundations in which they have two separate models to follow, one for heated spaces, and one for unheated spaces like an attached garage.
To me, if a garage is attached, it will share common walls and roof elements with the house. Despite this, in order to meet their models, a concrete garage slab is always completely isolated from the house concrete slab by vertical foam insulation. I guess this is done to decouple the garage slab from the house slab for thermal reasons, but does this make sense from possible differential movement between the two slabs?
