I am thinking of buying a 24' x 34' house built on a slab foundation and want to add a 17' x 34' ell that would also be on a slab foundation. Can the slabs be joined so there will be no shifting over time?
I'd suggest that it is structural engineer, or very experienced concrete installer, time. You will probably be tying slabs, foundation walls and footers together, using rebar, a concrete drill, and epoxy. This, as mentioned above, is not a huge deal, but it needs to be right.