Most decks are designed and built to be “decks” and therefore intended to support the weight of you and your lawn furniture perhaps. A similar format of room that we might build is done so under much more stringent and excessive engineering criteria, taking into account variables such as soil bearing capacity, the dead load of the room itself, and the live load of the worst 100 year snow fall in your geographic area. In reality, a significant percentage of our projects are supported over a substructure quite similar to that of a typical wood framed deck; we typically call this a suspended insulated sub floor. In all instances, this sub floor has a significant and permanent frost protected foundation and/or footing under it. The foundation we speak of can be in the form of a typical concrete pier or helical pier, a full perimeter foundation in a crawl space or slab on grade format, and in some instances, a full basement. Each application has its own particular set of variables and, like everything else in this process, is a matter of personal preference that is driven by your particular site conditions.