I'm trying to help a family member make the best choices for their new house.  They are in the construction phase and would like to have slab insulated underneath and at the edge (especially along the walkout section of the wall).

I had suggested they get a notch in the stem wall to accomodate some edge insulation at the back (where the walkout is).  At first it seemed like the advice came too late. Then I heard that they actually have a 1/2 notch in the wall?  I'm not sure what that means?

My initial thought was that the notch only aligns the edge insulation with the framed/insulated wall above it to try to prevent an easy path for heat loss, and adding the edge insulation between the frostwall going down and the floor slab wouldn't be a problem regardless of how thick it was installed....  but they are getting pushback from the builder that at the back walkout wall, the basement floor cement needs to at least catch the edge (be partially supported ) by the stem or frost wall.   

I would have guessed that the basement floor is not load bearing other than people and furniture, and could be supported by compacted fill (gravel/sand/whatever), poured in a totally insulated "tub", and edges wouldn't need to rest on or be supported by a wall/foundation/footing.

Can anyone give some light on this, or help explain ?  Is it a code issue?  Location is West Michigan.

Thank you!