The add on rooms do not include a floor, though you are welcome to use a tarp or floor liner inside. The size is 8'x8', so most customers will use a 9x8 tarp or a 10x10 tarp if you want it to overlap more. The stove takes up a lot of room when used, it drops the person capacity from 8 to 4 since you need a safe distance from the stove. I would recommend using a pad or a cot instead of an air mattress if using the stove.