Granny flats — or secondary dwellings — are one of the most searched renovation topics in Australia, and for good reason. They offer rental income, family accommodation, and meaningful property value without requiring a full subdivision or new land purchase.
But the approval process, size limits, and rules vary significantly between states — and getting the wrong information early can waste time and money.
This guide covers the key rules in NSW, Victoria, and Queensland as of 2025 — clearly, without jargon.
What counts as a granny flat in Australia?
The term "granny flat" is informal. In planning law, the correct term is secondary dwelling — a self-contained residential unit that is located on the same lot as a primary dwelling and is ancillary to it. Self-contained means it has its own kitchen, bathroom, and sleeping area. Ancillary means it\'s associated with — and subordinate to — the main home on the block.
Secondary dwellings can be attached to the primary dwelling (a converted garage, a ground-floor addition), detached (a separate structure in the backyard), or in some cases located above a garage or carport. The physical form affects the approval pathway and the cost.
The rules that govern secondary dwellings — size limits, setbacks, approval pathways, and permitted uses — vary significantly between NSW, Victoria, and Queensland. What\'s straightforward in one state may require a full planning permit in another. The sections below cover each state separately.
Granny flat rules in New South Wales
In NSW, secondary dwellings are governed by the State Environmental Planning Policy (Housing) — commonly referred to as the Housing SEPP. This policy was introduced to streamline the approval process and make it easier for eligible homeowners to build a granny flat without going through a full Development Application.
The Complying Development pathway is the faster route. If your block meets the eligibility criteria — generally a minimum lot size of 450m², a primary dwelling already on the land, and compliance with setback and height requirements — you can obtain approval through a private certifier rather than waiting for council. Approval can sometimes be granted in days rather than months.
The maximum size for a secondary dwelling under the CDC pathway is 60m² of floor area. This is a hard limit — not a guideline. If you want something larger, you'll need to go through a full DA, which involves council assessment and is subject to local planning controls that may or may not permit it.
NSW has seen several reforms to secondary dwelling rules in recent years, with the general direction being toward greater permissibility. Always confirm current rules with your local council or a qualified planning professional — the rules that applied two years ago may not be the rules that apply today.
Rules change. Always confirm current requirements with your local council or a qualified planning professional before making any decisions based on this article.
Granny flat rules in Victoria
Victoria's approach to secondary dwellings is more complex than NSW's. In most residential zones, a planning permit is required to build a second dwelling on a lot — and the assessment process involves council discretion rather than a simple compliance check.
The ResCode (Residential Code) sets out requirements for siting, setbacks, overlooking, overshadowing, and private open space. These requirements apply to secondary dwellings in the same way they apply to primary dwellings, and they can significantly constrain what's possible on a given block — particularly smaller or irregularly shaped lots.
Some zones and overlays in Victoria do allow secondary dwellings without a planning permit, subject to conditions. Whether your property falls into one of these categories depends on your specific zone, any overlays that apply, and the size and configuration of your block. This is not something to assume — it needs to be confirmed with your local council or a town planner.
Victoria has been reviewing its secondary dwelling policies as part of broader housing reform discussions. The rules in your specific council area may differ from the general state framework. Always verify current requirements locally before investing in design.
Rules change. Always confirm current requirements with your local council or a qualified planning professional before making any decisions based on this article.
Granny flat rules in Queensland
In Queensland, secondary dwellings — often called "secondary residences" or "auxiliary units" — can be accepted development on eligible lots, meaning they may not require a full development application. The maximum size for accepted development is generally up to 80m², which is more generous than NSW's 60m² limit.
Brisbane City Council has its own specific rules under the Brisbane City Plan. Whether a secondary dwelling is accepted development, code assessable, or impact assessable depends on the zone your property is in, the size of the lot, and the proposed size and siting of the dwelling. The BCC planning scheme is detailed and specific — a general understanding of Queensland rules is not sufficient for Brisbane properties.
Outside Brisbane, rules vary significantly by council. Some regional councils are more permissive; others have stricter controls. If your property is in a flood-affected area, a bushfire-prone area, or subject to a heritage overlay, additional requirements will apply regardless of the general zone rules.
Queensland has been actively reforming its planning framework to address housing supply, and rules have changed in recent years. As with all states, always confirm current requirements with your specific local council or a qualified town planner before committing to a design.
Rules change. Always confirm current requirements with your local council or a qualified planning professional before making any decisions based on this article.
What affects whether your block is suitable?
State rules set the framework, but whether your specific block is suitable for a secondary dwelling depends on a combination of factors that need to be assessed individually. These are the seven most common constraints:
Block size and shape
Most states have minimum lot size requirements for secondary dwellings. Irregular shapes — narrow frontages, L-shaped blocks, or lots with significant slope — can make it difficult to meet setback requirements even on otherwise eligible blocks.
Zoning and overlays
Your property's zone determines what's permitted as of right and what requires a planning permit. Overlays — flood, bushfire, heritage, environmental — add further constraints that apply regardless of the underlying zone.
Setback requirements
Secondary dwellings must meet minimum setbacks from property boundaries, the primary dwelling, and the street. On smaller blocks, meeting all setback requirements simultaneously can be the binding constraint on what's buildable.
Existing structures on the land
Sheds, garages, pools, and other structures count toward site coverage calculations. A block that looks large enough on paper may have limited buildable area once existing structures are accounted for.
Flood, bushfire, or heritage overlays
These overlays can significantly restrict what's permitted, require additional engineering or design requirements, or in some cases prevent secondary dwellings entirely. They must be checked before any design work begins.
Stormwater and services connections
A secondary dwelling needs its own or shared connections to water, sewer, and stormwater. The cost and feasibility of these connections depends on the existing infrastructure on the block and the distance to mains services.
Easements
Easements — for drainage, services, or access — restrict what can be built over or near them. They're registered on the title and must be checked before any design is finalised. Building over an easement without approval can require costly demolition.
How the approval process works — step by step
The general process for approving and building a secondary dwelling follows a consistent sequence across all three states, though the specific pathway — and the time each stage takes — varies significantly by council and approval type. Complying Development in NSW can move in weeks; a full DA in Victoria can take six months or more.
Feasibility check
Confirm the block is eligible — zone, overlays, size, setbacks, easements. This happens before any design work begins.
Design
Develop a design that meets the approval pathway requirements and works with the block's specific constraints.
Application — CDC or DA
Submit the application through the appropriate pathway. CDC applications go to a private certifier; DA applications go to council.
Approval
Receive approval with any conditions. Conditions must be addressed before or during construction.
Construction certificate
Obtain the construction certificate (or building permit in VIC) before work begins.
Build
Construction proceeds with inspections at required stages — footings, frame, waterproofing, final.
Occupation certificate
The final certificate confirms the dwelling is compliant and can be legally occupied or rented.
Timelines vary significantly. A CDC in NSW can be approved in 10–20 days. A DA in Victoria or Queensland can take 3–9 months depending on council workload and the complexity of the application.
Common mistakes that slow down granny flat projects
Most delays and cost blowouts in granny flat projects are avoidable. These are the mistakes we see most often:
Assuming all blocks qualify
Block size is just one factor. Zoning, overlays, setbacks, and existing structures all affect eligibility. A block that looks suitable often isn't — and discovering this after investing in design is expensive.
Skipping feasibility before investing in design
Design costs money. Spending $5,000–$15,000 on architectural drawings before confirming the block is eligible is a common and avoidable mistake. Feasibility first, design second.
Using a builder unfamiliar with the approval pathway
The approval process for secondary dwellings is specific. A builder who doesn't understand the CDC or DA pathway — or who doesn't know the local council's requirements — will slow the project down and may give you incorrect advice.
Underestimating total cost
The build cost is only part of the total. Design fees, council fees, certification, services connections, and landscaping can add $20,000–$40,000 to the project cost. Budget for the full picture, not just the construction.
Not checking easements before purchasing or planning
Easements are registered on the title and are publicly searchable. Checking them takes minutes. Not checking them — and then discovering a drainage easement runs through your planned building footprint — can derail an entire project.
How Japan Homes approaches granny flat projects
Every granny flat project we take on starts with a feasibility conversation — not a design conversation. Before we talk about floor plans or finishes, we research your specific block: the zone, any overlays, the setback requirements, the easements, and the most appropriate approval pathway. If the block won\'t work, we tell you that upfront — before you\'ve spent money on design. We\'d rather have that conversation early than have you discover it six months in.
If the block is suitable, we manage the full process — from design through approval through construction through handover. We work across Sydney, Melbourne, and Brisbane, and we understand the specific council requirements in each market. You have one point of contact throughout, and we don\'t hand off once the sale is made.
The bottom line
Knowing the rules before you invest in design or build saves significant time, money, and frustration. The approval framework for secondary dwellings in Australia is navigable — but it requires understanding the specific rules that apply to your block, in your state, under your council\'s planning scheme.
This article provides general guidance only — not legal or planning advice. Always verify current rules with your specific local council or a qualified town planner before making any decisions. Rules change, and the information that applied when this article was written may not reflect the current position in your area.
Wondering if your property qualifies?
Japan Homes offers a free feasibility conversation — we research your specific block and give you an honest answer before you commit to anything.
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