I have a deck that is approximately 20" high from grade level and want to add 2 steps. I'm in Mt Airy MD which has a frost depth of 32. I plan to use stringers for the stairs and wanted to know about the last step landing and the concrete pad or footings and whether that has to be 32" deep too as are all the footings for the deck. Its a freestanding deck with no ledger attachments to the house