If 5 inches has been suggested as the minimum, then that would be Ontario building Code spec. I prefer the Holmes on Homes school of thought on the subject and would go with pads either 18x 18, or 24x24, poured to a depth of 10-12 inches as far up as grade before the floor goes in. There would also be a heavy amount of mesh and rebar added in. The absolute best would be piers around the 4 foot mark for depth in the hole to avoid any frost heave action but the cost of the 'crete for something like that is probably evil to hideous in $$$$ CDN. I did a modular pour for a mezzanine level sidewalk and steps project several years back and it took around 125 bags of 66 lb premixed concrete to complete the job. And it was all hand mix and pour!
Best of luck with your project and be sure to have all the inspections done and signed off on. All it takes is one self-officious minor functionary in planning and development to allege that the paperwork isn't in order to ruin your summer with petty bureaucrap.
Nick
Best of luck with your project and be sure to have all the inspections done and signed off on. All it takes is one self-officious minor functionary in planning and development to allege that the paperwork isn't in order to ruin your summer with petty bureaucrap.
Nick