Can site works or excavation start before Building Approval?

Generally, no, if the site works or excavation form part of building work requiring Building Approval. ACT Planning states that building work can start once the commencement notice has been received.

For a dual-occupancy project, excavation for foundations, footings or other construction forming part of the approved building work should therefore not start before the required BA and commencement notice are in place.

However, not every activity carried out on a site is necessarily “building work.” Whether preliminary works can occur earlier depends on what the work involves, whether it requires a separate approval, and any conditions of the Development Approval that must be satisfied before construction starts. ACT Planning specifically says DA conditions may impose requirements that must be met before any construction or building work can start.

Reference: ACT: Building Approvals - https://www.planning.act.gov.au/applications-and-assessments/building-approvals