Granny flat permit rules by state: the planning maze that decides whether the math actually works

Two identical 700 m² blocks one state apart can give two completely different answers to 'can I put a granny flat on this?'. NSW has the country's friendliest secondary dwelling regime. Victoria effectively bans rentable granny flats unless they are classed as movable units. Queensland allows them but mostly through a full development application. The state planning rules, not the build cost, decide whether a granny-flat investment is viable on a given block.

Investors who chase the cost numbers without first checking the permit pathway often discover that the version of the project they costed is not the version they are allowed to build. A 60 m² unit that pays for itself in eight years on a Sydney CDC pathway is the same 60 m² unit that quietly becomes a $200,000 family-only annex in Melbourne. The build is the same. The planning framework is the difference.

NSW: the country's friendliest pathway

New South Wales runs the State Environmental Planning Policy (Affordable Rental Housing) 2009, usually called the Affordable Rental Housing SEPP or the granny-flat SEPP. It sets a complying-development pathway for secondary dwellings up to 60 m² on lots of at least 450 m², with no requirement that occupants be related to the main house.

• Complying Development Certificate (CDC): approval through a private certifier in around 10 to 20 business days where the proposal sits inside the SEPP envelope. Setbacks, height, and site coverage are prescriptive.
• Development Application (DA): required where the lot is below 450 m², a hazard overlay is triggered, or design controls in the local LEP override the SEPP. DAs typically run three to six months and cost meaningfully more in design and reports.
• Rentability: the secondary dwelling can be let on the open market, including to strangers, subject to council notification in some areas.

Victoria: dependent person's unit only

Victoria treats the same physical structure differently. Under the Victoria Planning Provisions, a granny flat is a 'dependent person's unit' (DPU) and must be occupied by a person dependent on a resident of the main dwelling. That is the legal definition. Letting it to a non-dependent tenant breaches the planning permit and is enforceable by the council.

The VicSmart movable-unit pathway streamlines portable granny flats up to about 50 m², on the understanding the unit can be removed when the dependency ends. The rentability restriction is the same. A Victorian investor building a DPU is building family accommodation with no rental income to underwrite it.

The practical consequence is that the granny-flat-as-investment thesis does not work in Victoria as it does in NSW or WA. The same build cost produces a depreciable capital improvement and a possible resale premium, but no weekly rent. Investors looking for a second-income dwelling in Victoria are usually pointed toward subdivision or a townhouse build instead. The related read on subdividing and battle-axe blocks sets out that pathway.

Queensland: council-by-council with a DA bias

Queensland uses the term 'secondary dwelling' or 'auxiliary dwelling', governed by the Planning Act 2016 and individual council planning schemes. The Brisbane City Plan, Logan Planning Scheme, and Ipswich Planning Scheme allow rentable secondary dwellings on larger lots, typically 600 m² or more, but most still require a code-assessable or impact-assessable DA rather than a fast-track certificate.

Smaller regional councils often restrict secondary dwellings to family-only occupation, mirroring the Victorian model. Approval timelines run two to four months on a clean code-assessable application, longer where neighbour notification triggers. The build envelope is generally more generous than NSW (some councils allow 80 m² to 100 m²), but the permit cost and time eat into the yield uplift.

WA: ancillary dwelling under SPP 3.1

Western Australia uses State Planning Policy 3.1 and local R-Code overlays. Ancillary dwellings up to 70 m² on lots of at least 450 m² are permitted in most metropolitan Perth councils, with rentability to non-family occupants allowed in the majority of LGAs. The approval pathway is relatively streamlined for code-compliant designs and often clears in six to eight weeks.

The 70 m² cap is the largest in the country for a streamlined approval pathway, which is part of why the Perth granny-flat rental market is comparatively active and yields hold up against detached-house rentals on a per-m² basis.

SA, TAS, ACT, NT in short

• South Australia: small second dwellings under the Planning, Development and Infrastructure Act, generally up to 60 m². Most metro Adelaide councils allow rentable units; outer-zone councils vary.
• Tasmania: ancillary dwellings under local planning schemes, generally up to 60 m². Hobart and Launceston allow rentable units; smaller councils often restrict to family.
• ACT: secondary residences in RZ1 and RZ2 zones, up to 90 m² gross floor area. Rentable. A lease variation may apply on Crown lease land.
• NT: self-contained accommodation under the NT Planning Scheme is generally permissive. Cyclone-rated construction adds cost above the national baseline.

The approval costs nobody quotes upfront

Builders quote build prices. Councils, water authorities, and certifiers quote everything else, and the everything-else can add 15% to 30% on top of the build contract. The Sydney pathway is typical of the larger capitals:

• Pre-DA or pre-CDC consultation: $500 to $1,500 if the certifier or council offers it.
• Architect or draftsperson plans: $3,000 to $8,000, more for sloping or constrained sites.
• Section 7.11 or 7.12 contributions: $5,000 to $15,000 per dwelling depending on council; inner-ring councils are at the top of that range.
• Building approval or construction certificate: $1,500 to $3,000.
• Sydney Water or equivalent headworks: $7,000 to $25,000 where new connections are needed; the number jumps sharply if a sewer main extension is required.

Mid-range total for these line items on a clean Sydney CDC pathway: roughly $18,000 to $28,000 on top of the build cost. A useful sense-check is to add these into the buying cost calculator as the build-side equivalent of stamp duty: real money, rarely surfaced in the headline pitch.

Common knockouts

• Lot size below the state minimum: no CDC, often no DA either. The state floor is jurisdictional.
• Bushfire or flood overlay: a full DA with BAL assessment, flood study, or both. The reports alone are $2,000 to $6,000 and the design controls tighten.
• Heritage or character area: external form and materials are controlled. Approval still possible, but the streamlined pathway closes and the design budget rises.
• Setback or site-coverage breach: triggers a full DA even where the SEPP or equivalent would otherwise apply.
• Sewer or stormwater constraints: an easement variation can take longer than the build itself, and Sydney Water in particular is not fast.

Title encumbrances and existing easements are a separate check. The companion piece on easements, encumbrances and caveats covers what to read on the title before the architect starts drawing.

How the state rule changes the investor math

The yield arithmetic is the same shape everywhere; the inputs differ by jurisdiction. In NSW on a 600 m² Sydney middle-ring block, the worked example looks like this:

• Main house purchase: $1,050,000. Current rent $720/wk, $37,440/yr.
• Add a 60 m² granny flat. Build cost $185,000. Contributions plus headworks $19,000. Design and approvals $9,000. Total add: $213,000.
• Granny flat rents at $620/wk, $32,240/yr.
• Combined yield post-build: ($37,440 + $32,240) / ($1,050,000 + $213,000) = $69,680 / $1,263,000 = 5.52%.
• Yield on main alone: $37,440 / $1,050,000 = 3.57%.
• Yield uplift: 1.95 percentage points.

Capital uplift on resale is a separate question. A common rule of thumb is that a granny flat lifts the valuation by around 60% of its construction cost in the first few years, so $213,000 spent might add roughly $128,000 to appraised value at sale. That is an $85,000 short on the capital side at year one, recovered through about three years of net rent before the position is whole. The investor running this scenario is buying a yield improvement, not a capital arbitrage. Run the same numbers against your own purchase price and expected rents on the rental yield calculator before signing a build contract.

In Victoria the same physical project produces $0 of rental income because the DPU restriction blocks letting. The $213,000 spent becomes a depreciable capital improvement with no offsetting rent. The resale premium may still be there, but the negative-gearing position is weaker because the build does not generate assessable income. The negative gearing calculator is the right place to model the difference.

The companion piece on granny flat investment economics runs the full holding-period math; this article is the permit-side prerequisite to it. Depreciation treatment is worth a separate read in depreciation schedules for investment property, because a new build attracts the full Division 43 capital works deduction the existing house no longer does.

What to do before you commit

• Pull the council's planning scheme or LEP and read the secondary-dwelling clause directly. The state framework sets the floor; the council can tighten it.
• Order a Section 10.7 (NSW) or equivalent planning certificate. It surfaces the overlays that knock out the streamlined pathway.
• Check the title for easements, covenants, and caveats. A sewer easement under the proposed footprint is the most common silent killer.
• Get a quote from a private certifier as well as the council. In CDC jurisdictions, the certifier is the faster route by a wide margin.
• Run the yield with the realistic post-permit timeline, not the builder's. A six-month DA pushes the income start date out by six months of holding cost.

The state rule is the first filter and the cheapest one to apply. Spending an afternoon on the council planning scheme is the difference between an investment thesis that survives contact with the planning portal and one that quietly dies on the approval pathway. The build is easy. The permit is the project.