I have an attached deck off of the dining room with a slider door. The deck is anchored on two corners with concrete pillars 3' deep. The other side is attached to the house rim joist with the deck 2x8 rim joist. I want to close this deck in and make it a 3 or 4 season room. Should I tear the deck out and put down concrete slab with block foundation or would it be ok to lay a subfloor over deck and build walls off that? No real load would be applied other than couple of chairs and ratan couch.