The foundation rest on the footing which is usually poured directly on the ground surface. In most residential constructions no stone backfill should be found under the footing. The walls of the foundation rest on the footing.
The backfill under the basement slab is usually composed of a 3/4 inch net DB stones. The backfill serves as a drainage bed and protects against the ground-level humidity which tends to seep into the house.
If your building has a street-level garage, the garage slab is not placed on the same level as the basement slab. The backfill under the garage slab may be more than one metre in depth and should be composed of 3/4 inch DB stones.
In some types of buildings, the garage is on the same level as the basement. In this case, the same type and thickness of backfill will usually be found under both slabs. There should also be a deeper excavation near the garage door, to guard against heaving caused by freezing.