I am building a garage for someone soon.
The mason has informed me that since it is
not tied into the house there is no need to dig down to the frost depth of 42"and lay block. An 18" rat wall is all that is required. There is a large maple tree about 8' away from where we are building and we would probably hit less roots going shallow.I don't know if the slab would crack too much without a solid foundation or not.