Ideally, you want the foundation to last long ... The simplest is to pour the slab directly on grade. In this case, you have to clear the topsoil, excavate to a depth of over a foot or so ...

footings and under-slab fill where a perforated sump basket collects it for pumping away from the house, or drained to daylight if your home's on a hill. Wood foundations require foundation-grade ...

One of the big reasons for that is Nault is removing all the common areas from the school in the New Sudbury neighbourhood and converting it into 20 rental units that are slab-on-grade ...