We have a Colonial house. Some of its built on an original small basement (1928) and the rest on slab where there were additions done. We are eventually looking to add a screened porch off the back of the house with addition on top that connects to our existing second story. But we could use more space in the basement. So is it better if we dig footings for that or is it better to just dig another basement for that addition (which could easily connect to our existing basement) for the covered porch second story addition to go on? Wondering what price difference is between that and just having footings ?