shed redo

Our backyard shed must be redone. The trim is rotting and the roof leaks. The problem after demolition is what do do with the left over rock. There is an attached fire pit made of rock and mortar. Also one of the shed walls is made of cinder block. The demo of this won't be fun. The plan is to completely demo the shed and make a bigger one and possibly add a kid-sized playhouse above. Some dimensions thrown around are 10X14. I haven't decided on foundation yet. One idea is to use pre-cast concrete blocks over gravel pier/footings. Another idea is to pour new piers. The 2nd floor will hang from the 1st with 2X6 joists and hangers. The roof will likely be simple gable to match the pitch of the house.