I have a garage that is separated from the house by a breeze way. The breeze way and garage are 6" below the house slab. That puts the front of the breeze way and garage almost below grade. I want to pour a slab over the exsisting slap, both the breeze way and garage. My question is; what is the best or most sound way to handle the concrete that is going to be poured up to the garage wall? Do I nail some 2x6s between the studs on edge flush to the outside of the garage wall creating a "form board", making the breeze way and garage two separate slabs. Or, can I just let the concrete go between the studs and knock out the breeze way and garage at the same time.
Thanks for any input. PW

You should make the breeze slab independent from the garage slab. As for the interior of the garage, don't let the concrete go between the studs. Concrete can rot the wood.

You can use 3/4' rigid insulation or pressure treated as a form board.

When you pour, you should spread a layer of gravel to separate the original slabs. You will make the slab "float".

The gravel layer depth is up to you. Maybe go 2" so you only have to pour 4" of concrete.