Victoria's planning rules changed to make small second dwellings — what most people call granny flats — much easier to build. In many cases a planning permit is no longer required. But a very common misunderstanding has followed: a building permit is still required, every time. And that permit needs engineered structural documentation.
Here's what the change actually means for homeowners.
What is a "small second dwelling"?
In Victorian planning terms, a granny flat is now a small second dwelling — a self-contained home of up to 60 square metres, with its own kitchen, bathroom and toilet, on the same lot as an existing house. It can't be subdivided onto its own title or sold separately.
The reform removed the old "dependent person's unit" restrictions, so occupancy is no longer limited to a dependent relative.
What changed — and what didn't
What changed: in many residential situations, a small second dwelling no longer needs a planning permit, provided the lot and the proposal meet the criteria and no special controls apply.
What didn't change: you still need a building permit before construction begins. There is no exemption. And planning exemptions don't apply universally — flooding, environmental, heritage and other overlays can still trigger a planning permit, so the first step is always confirming what applies to your specific lot with your council.
This is where people come unstuck. "No planning permit" gets heard as "no approvals," and then the project stalls at the building permit stage because the documentation isn't there.
What the building permit requires
A small second dwelling is classified the same way as a house, so it's assessed with the same rigour. A building permit application typically needs architectural drawings, a soil report and site classification, structural details for footings and framing, stormwater and drainage design, and energy efficiency documentation — plus compliance with current siting, safety and liveability requirements under the National Construction Code.
In other words: a granny flat is engineered like a small house, because that's effectively what it is.
Where the structural engineer comes in
Your structural engineer designs the parts that carry load and provides the documentation your building surveyor needs:
- Footings and slab, designed to your site's soil classification under AS 2870
- Wall, floor and roof framing
- Beams and lintels over openings
- Any structural considerations from siting — such as building close to boundaries, near existing structures, or over sloping ground
Our residential structural engineering team designs small second dwellings across Melbourne, and can coordinate the stormwater and drainage design at the same time.
Site issues that catch people out
Two things are worth checking before you finalise a design. First, easements — many suburban blocks have a sewer or drainage easement along the rear or side boundary, exactly where people like to put a granny flat, and building over one needs separate authority consent. Second, soil and slope — a reactive clay site or a fall across the block affects the footing design and therefore the cost and buildability.
Both are much cheaper to resolve on paper than after the design is locked in.
Planning a granny flat in Melbourne? Talk to a Melbourne structural engineer about the structural design your building permit will need.
Frequently asked questions
Do I need a planning permit for a granny flat in Victoria? Often no — small second dwellings up to 60 square metres are exempt in many residential situations. But overlays and site-specific controls can still require one, so confirm with your council.
Do I need a building permit for a granny flat? Yes, always. There is no exemption, and construction can't begin without it.
Do I need a structural engineer for a granny flat? Yes — the building permit requires structural documentation for footings, slab and framing, designed to the relevant Australian Standards.
Can I rent out a small second dwelling? Under the current framework there's no occupancy restriction of the old "dependent person's unit" kind, but tenancy rules apply. Check the current requirements with your council or a planning professional.
Can I subdivide and sell it separately? No. A small second dwelling must remain on the same lot as the main house.
