Why this question matters
A planning permit is the slow part of an extension. It can add months, neighbours can object, and it changes how carefully the design has to be argued. A building permit is the one every project needs anyway: a building surveyor checks the design against the Building Regulations, usually in a few weeks.
So the first thing worth knowing about any house is which of those two paths it's on. Since 8 September 2025 that has been a much clearer question in Victoria.
The rule that changed
Amendment VC282 set a single statewide trigger for one house in the main residential zones: on a lot of 300 m² or more, building or extending one dwelling doesn't need a planning permit under the zone. The siting rules — setbacks, walls on boundaries, site coverage — are then checked by the building surveyor instead of council.
Under 300 m², a planning permit is needed, but if the design meets the 12 Clause 54 standards it can go through VicSmart: a 10-day decision with no notice to neighbours and no objections.
What still brings a planning permit back
Overlays. A Heritage Overlay or Neighbourhood Character Overlay always does. Flooding overlays almost always do. Others — Design and Development, Significant Landscape, Bushfire Management — depend on their schedule or the size of the work, so the check flags them for a closer look rather than guessing.
More than one dwelling on the lot. Extending a unit, or a house that shares its lot with another, needs a planning permit.
A big tree near the back fence. Since September 2025, removing or lopping a canopy tree — over 5 m tall, with a trunk more than 0.5 m round and a canopy at least 4 m wide — needs a permit if its trunk is within 4.5 m of the rear boundary. That's VicSmart, with no objections, but it's a permit. The map can't see your trees, so check this yourself.
What this check can't see
Your title. Restrictive covenants and section 173 agreements are registered on the title, not in the planning map, and either can limit what you build. Read your title before you plan anything.
Easements and services. Sewers and drainage easements often run along the back of a lot, which is exactly where extensions go.
Whether the design complies. A building-permit-only path still means meeting every Part 5 number. Most of the skill in these projects is fitting a good house inside them.