I would like to make an extension for our house entry. Our home is a split-level type of house, and the entry is super small (no space for a closet. You enter the house, and there's around 3 feet of space before having to go up or down). That's why we are thinking about extending the entry a little bit (we would like to "extrude" our entry around 4-5 feet towards the outside of the house...so that would be a very small extension.)
We have a concrete slab in front of the door, on the outside that is 125 inches wide X 48 inches, and 6 inches thick. Around 3 inches of it is in the ground. The slab has been there for decades and never cracked.
My plan was to extend the current concrete slab so that we have a bit more space for the extension. Thing is, I don't know how concrete slab works in climate like mine. I live in Canada-Quebec, and during winter, it can get really cold with a lot of snow.
My guess is that I shouldn't build on top of that already existing slab, since it's not deep enough. I've also heard that I should insulate the slab or something like that, to prevent it from moving as much as possible since we want to build on top of it.
So my question is...should I remove the current slab and poor a new one? Or can I simply extend the current slab, even if it's not very deep in the ground, and build on top of it?
If I must poor a new one, how deep should it be, and do I need to add some insulation material around it so that the ground doesn't touch the concrete directly to prevent it from moving or cracking during winters and on spring when it gets hotter and the ground start to unfreeze?
Hopefully it's not too confusing. I've seen a lot of videos on Youtube on how to make house extensions, but most of them were kind of big extensions. Like full rooms. Mine would be around the size of the current slab (125"x48") more or less. That's why I'm confused about the type of "foundation/concrete slab" I need for this.
Thank you very much!