It is my understanding that a slab should be independent of the foundation wall and footing so that setttling or other movement can do its thing. I have seen foundation details where the slab is attached to the wall with dowels making the two pretty much composite. How should this be viewed- good, bad or ugly? In Washington State, at least,the slab has to have thermal isolation from the wall so that is another reason to keep the two separate.

Here is a secondary question as well: In a thickened slab footing do you maintain the same layer of gravel and moisture barrier through the trench?

Thank you in advance