I rmoved the roof from my ranch house and put a second floor on that is cantilevered 2 feet in the back. I had a architeect draw the plans and got my permits. So right now i have the second floor on windows in tyvek on and shingles on (weathertight). Now I am trying to put a 10 foot by 6 foot mechanical closet off the back to house the furnace and oil tank and water heater because the house is on a slab. Could anyone give me some suggetion on whether i can just pour a concrete pad to build this on or do i need a foundation with footings? Could i just use sona tubes and build something like a deck and then build my walls on top of that.