I'm using 8" durisol block for foundation. The garage is located downtown Toronto.
Engineers take several factors into consideration when determining a footing's width and depth. There would be notes and hopefully a cross section detailing the footings and their related assemblies on the design / drawing. If you're at the homework stage trying only to get a feel for things prior to committing to build something, I suggest having a meeting with a BCIN designated person (Engineer, architect, technologist, etc.) who could also prepare your drawings should you move forward with the project. We've prepared footings from 8 inches to 2 feet + thick, so I wouldn't assume anything.
Hope this helps point you in the right direction.
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