I have a house that has a concrete front porch. I'm thinking of making the front porch an enclosed part of the house and the concrete slab would bear the load of a two story addition. I dug down 46" on the side of the porch to see if a foundation is present and there is a cement wall down to 46" below grade. I was not able to detetermine if a footing is also there. I used a 8' piece of ribar and hammered all the way down along side the foundation wall but I did not hit a footer. Could the porch be a monolith pour (down to at least 46")?
It would be unusual for a contractor to build a monolithic porch, since that would waste a lot of concrete. The fact that the exterior of the porch goes down to approximately 48 inches below grade suggests that the porch walls may be built like a basement, perhaps 6 or 8 inches thick, and support the top of the porch. In any case, if the porch foundation is not adequately built to support a two story house, you cannot use it safely, so you are going to have to find out the details of the construction of the porch. This may require additional excavation.