[caltomsmi]

Thanks.

[smoothy]

Someone doing that sort of work... really needs to be experienced in these sorts of things. Or they might fail and cause huge issues with the structure.

[caltomsmi]

Its hypothetical, I just need to know how, I'm not actually going to do it

[smoothy]

They will all be mechanical ties. Some better than others. Some more suitable in certain situations than others.

[ma0641]

If it is a slab, foundations are usually extended by coring into the old slab and tying rebar to the new foundation. Footing the same. If a block wall, they should remove every other corner or wall section block and connect the new wall to it. Sometimes they use bent rebar and fill the block cores.