Good morning,

I am getting ready to form up for my first house. Originally I was going to build a 36″ high perimeter foundation for a crawlspace, but have since decided I would rather put it on a slab. The slab would be a 34’x32′ overall area but I am a bit confused in looking at the code as to what my minimum required footing width is. One half of the building has a second floor, but given that the first floor bears directly on the concrete and there is no built up first floor to support, do I still need to follow the specifications for a two story building? This design also means that the center interior wall of the building supports the second story exterior wall. I presume this means I need a footing running through the middle of the slab under the first story dividing wall. Is this correct?

The code here says I need to get the footing to 18″ below grade below the frost line, which seems excessive in my case as we are very close to the ocean in the Gulf Islands on a property filled with 4″ crush, sand, and several inches of 3/4″ road fill. There are absolutely no drainage issues around the building site and we rarely get extended periods of frost. Ideally I would just pour a monolithic slab with a built up center and 3″ of insulation, with a 12″ thick perimeter footing extending 8″ below grade, and add a few extra lengths of 15mm rebar through the center line where the extra floor requires support.

Does anyone have any thoughts about the best way to go about this? Any advice is greatly appreciated.

I should mention that I am in an unincorporated district of British Columbia, so there are no inspections here to speak of. However, I am not looking to cut any corners that will have an impact on the structural integrity or resale value of the home. The building site is on compacted gravel that is well settled, where a previous home had sat and has since been demolished.