I have a home that was built in 1925 and has a poured foundation. It has a clearance of about 6'2" interior so I know that exterior it is below frost. (I live in Vermont). My question is is it acceptible to put an on grade slab next to the poured foundation if the construction on the slab will be attatched to the existing house? We would like to build an addition but aren't sure if we want to do another basement, crawl space or just a slab. Any info on ths or links to info would be appreciated a lot. In terms of attaching the two basements, (should we chose that route), the existing foundation has 16" thick walls, filled with all sorts of rocks,etc. for filler. This is what would deter us from going with another full basement.

You will need to consult your local building dept. but I believe for an addition that is attached to the house you will need a foundation that goes below frost. You could then pour a concrete floor with no crawl space or basement if you wish.