Not sure which you need?
Start with how the house is built. If it has a timber floor on stumps, the work is restumping, also called reblocking: replacing the stumps and re-levelling the floor. The BPC registers restumpers for both in one class (BPC). If the house has brick walls on footings or a concrete slab, ask about underpinning, which works on the foundation itself: the footings under brick walls, or a slab.
Either way, the signs alone don’t tell you what a house needs. An inspection does. All three jobs need a building permit (Campaspe Shire building fact sheet), and the builder or a building surveyor usually arranges it.