The rules for building a granny flat in NSW are straightforward at the state level. Most standard suburban blocks qualify, approval can happen in as little as 10 to 20 business days, and there’s no requirement to house a family member. You can rent it to whoever you like.
Where it gets more complicated is on the ground, particularly in Newcastle and Lake Macquarie, where mine subsidence, flood mapping and bushfire overlays affect a significant number of properties. Those are the things that push a simple granny flat from a fast approval to a longer council process.
This article covers both. The state rules first, then the local factors that matter most in our area.
What Is a Granny Flat Under NSW Planning Rules?
In planning law, a granny flat is called a secondary dwelling. The formal definition under the State Environmental Planning Policy (Housing) 2021, known as the Housing SEPP, is:
A self-contained dwelling that is established in conjunction with another dwelling (the principal dwelling) on the same lot of land.
Self-contained is the key phrase. To qualify as a secondary dwelling, the building needs its own kitchen, bathroom, and living space. It can be inside the main home, attached to it, or completely detached in the backyard. All three configurations are permitted under the SEPP.
One secondary dwelling per lot. That’s the rule, and you can’t build two.
How Big Can a Granny Flat Be in NSW?
The maximum internal floor area for a secondary dwelling in NSW is 60 square metres.
That’s the number under the Housing SEPP, and it applies statewide. It covers internal living space (bedroom, bathroom, kitchen, living area) but excludes covered outdoor areas like verandas or patios, which can add usable space beyond the 60m2 limit.
Newcastle City Council’s Local Environmental Plan (LEP) applies its own floor area control alongside the SEPP. Under clause 5.4(9) of the Newcastle LEP 2012, the floor area of a secondary dwelling must not exceed the greater of 60m2 or 20% of the total floor area of the principal dwelling. On a large home this can mean you could potentially build slightly beyond 60m2 through a DA, but 60m2 is the standard working limit for almost all projects.
For context, 60m2 is enough for a comfortable one-bedroom or compact two-bedroom layout: a living/dining area, full kitchen, bathroom, bedroom, and a small amount of storage. It’s liveable. It’s not generous, but builders who specialise in secondary dwellings can do a lot with that space.
Note on the 85m2 figure that sometimes appears online: that applies only in the Western Sydney Aerotropolis precinct. It doesn’t apply anywhere in the Hunter region.
What Lot Size and Frontage Do You Need?
For a granny flat approved as complying development (the fast-track pathway), your lot needs to meet two minimum requirements under the Housing SEPP:
- Minimum lot area: 450 square metres
- Minimum lot width: 12 metres at the building line
Both must be met. A lot that’s 600m2 but only 10 metres wide doesn’t qualify for CDC.
The lot also needs to be in a permissible zone. Secondary dwellings under the SEPP are permitted in R1, R2, R3, and RU5 zones where a dwelling house is allowed. In Newcastle’s LGA, secondary dwellings are also permitted with consent in the C4 Environmental Living zone under the Newcastle LEP.
What about smaller lots? If your block is under 450m2 or the frontage is less than 12 metres, the CDC pathway is closed, but a Development Application may still be possible. It depends on whether the local council and its LEP support it. Lots under 450m2 can sometimes accommodate a secondary dwelling wholly contained within the existing principal dwelling, which has different rules. Worth discussing with your builder or a planning consultant before ruling it out.
CDC or DA: Which Approval Pathway Applies?
This is where most of the practical questions sit. NSW has two approval routes for granny flats, and which one applies to your block determines your timeline and cost.
CDC | DA | |
What it is | Complying Development Certificate, assessed against fixed state standards | Development Application, assessed by local council on merit |
Who approves it | Private certifier or council CDC team | Local council planning department |
Timeline | 10 to 20 business days (typically) | 6 to 12 weeks, sometimes longer |
Neighbour objections | Cannot block approval if standards are met | Submissions considered in assessment |
Flexibility | Low. Must meet every standard exactly | Higher. Merit-based, can vary from standard rules |
Cost | $2,500 to $5,000 (certifier fees) | Higher. Council fees plus additional reports |
Best when | Standard lot, no environmental constraints | Heritage, flood, bushfire, small lot, or non-standard design |
For most suburban properties in Newcastle and Lake Macquarie that sit on 450m2+ and aren’t in a constrained area, CDC is the right pathway. It’s faster, more predictable, and cheaper.
What Stops a Granny Flat Qualifying as Complying Development?
Even on a lot that meets the size and width requirements, several site-specific factors can rule out CDC and push you into a DA. The most common:
Flood-affected land. If your property is mapped as flood prone, CDC is generally not available. You’ll need a Flood Certificate (Part A and Part B in Newcastle) before any approval pathway can be confirmed. Newcastle City Council recommends obtaining a Flood Certificate early if your property is near flood-prone land, because it tells you the flood planning levels that any new dwelling must meet. The City of Newcastle’s secondary dwellings guide sets out the local requirements that sit on top of the state rules.
Bushfire prone land. Properties in bushfire-prone areas require a Bushfire Assessment by a qualified consultant. Secondary dwellings and dual occupancies in NSW have a maximum Bushfire Attack Level (BAL) of BAL-29 for CDC eligibility. Above BAL-29 (including BAL-40 and BAL-FZ), the CDC pathway closes and a DA is required.
Heritage. If your property is in a heritage conservation area or is heritage-listed, additional assessment is required. CDC is generally not available for heritage-affected sites.
Acid sulphate soils. Parts of the Newcastle and Lake Macquarie LGAs have acid sulphate soil classification. Technical studies are required before approval can proceed on affected sites.
Vegetation and tree constraints. Significant trees on or near the building footprint can affect approval. Council’s planning certificate will note any tree preservation orders or biodiversity values.
Lot geometry. Battle-axe blocks, irregular lots, and heavily sloped blocks can affect whether the setback requirements can be met. Setbacks for a secondary dwelling mirror those of the principal dwelling: typically, 3 metres rear and 0.9 metres to side boundaries for structures under 4.5 metres in height.
Extra Checks in Newcastle and Lake Macquarie
IMAGE: Local map or aerial view. Subject: Aerial showing typical residential lot in Newcastle or Lake Macquarie with a granny flat footprint visible in the backyard. Alt text: Aerial view of residential lot with detached granny flat, Lake Macquarie NSW
Newcastle and Lake Macquarie have a few site constraints you don’t encounter as often elsewhere in NSW. These are the ones worth checking early.
Mine Subsidence
Parts of Newcastle and Lake Macquarie sit over old or active underground coal workings. Subsidence Advisory NSW designates Mine Subsidence Districts across the area, and suburbs including parts of Wallsend, Cardiff, Glendale, Boolaroo, Speers Point and others carry mine subsidence classification.
If your property is in a Mine Subsidence District, you must get approval from Subsidence Advisory NSW before lodging your CDC or DA. This applies to any new structure, including a secondary dwelling. It’s a separate approval on top of the council or certifier process, not instead of it.
The practical implication: add Subsidence Advisory into your approval timeline. It runs alongside the council and certifier process but can add time if geotechnical information is required. For work built without the required Subsidence Advisory approval, compensation for future subsidence damage is at risk.
You can check whether a property is in a Mine Subsidence District through the NSW Planning Portal or by asking your builder to check when assessing site feasibility.
Flood Mapping
Lake Macquarie has a large proportion of properties near the lake foreshore and tributary waterways. Flood planning areas are extensive across the LGA, and a significant number of standard-looking suburban blocks carry flood constraints that aren’t obvious at street level.
On flood-affected sites, minimum floor levels apply (typically 500mm freeboard above the 1-in-100-year flood level), flood-compatible materials are required, and drainage management becomes part of the design brief. These requirements don’t necessarily stop a granny flat being built, but they add design requirements and, if CDC is unavailable, push the project into DA territory with additional assessment time.
Newcastle City Council also requires flood certificates for flood-prone sites before the approval pathway can be confirmed.
Bushfire
Bushfire-prone land exists in parts of both LGAs, particularly on ridgelines and at the urban-bush interface. As noted above, CDC is available only up to BAL-29. Above that rating, a DA is required and construction standards under AS 3959 apply.
Section 7.11 Contributions
Newcastle City Council applies Section 7.11 developer contributions to secondary dwelling approvals. These are contributions toward local infrastructure such as roads, parks and drainage, and they are charged at the time of consent. Lake Macquarie City Council also applies contributions to secondary dwelling approvals.
The contribution amount depends on the location and is calculated based on council’s current contributions plan. It’s worth factoring this into your budget early. In Newcastle, contributions for a secondary dwelling typically run several thousand dollars. Ask your builder or certifier to check the applicable rate for your suburb.
Can You Rent Out a Granny Flat in NSW?
Yes, and to anyone. There’s no requirement that the occupant be a family member.
The previous restriction that tied NSW granny flat approvals to “affordable rental housing” and limited tenants to family members was removed when the Housing SEPP was consolidated in 2021. A secondary dwelling can be rented on the open market, listed on a rental platform, or used however the owner chooses.
The only restriction is that the secondary dwelling cannot be subdivided from the principal dwelling and sold separately. It must remain part of the same lot.
If you’re thinking about rental income as part of the case for building, a 1-bedroom granny flat in Newcastle or Lake Macquarie typically returns $400 to $650 per week in the current rental market, depending on location, size, and standard of fit-out.
Can You Subdivide or Sell a Granny Flat Separately?
No. Under the Housing SEPP, a secondary dwelling cannot be subdivided from the principal dwelling. The lot cannot be split to create a separate title for the granny flat.
This is a firm rule, not something that can be varied at the council level. If you want to end up with two separately titled properties, you need a dual occupancy development rather than a secondary dwelling. That’s a different development type with different rules around lot size, design, and approval.
Dual occupancies can be strata-titled in some circumstances, but they require separate development consent, are assessed differently, and aren’t available as complying development on all lots. If separate titling is the goal, it’s worth discussing with a planning consultant or your builder early, because it affects the whole approach.
FAQ
Do I need a BASIX certificate for a granny flat?
Yes, in almost all cases. Every new secondary dwelling in NSW requires a BASIX (Building Sustainability Index) certificate before a DA or CDC can be approved. BASIX covers water efficiency, thermal comfort, and energy performance. It applies regardless of the size of the granny flat. A 30m2 studio and a 60m2 two-bedroom flat both need one. The certificate is generated through the NSW Planning Portal and typically costs $200 to $400 through a licensed assessor. Your builder can usually coordinate this as part of the approval process.
Can I build a granny flat on a battle-axe block?
Possibly, but it depends on the lot dimensions. A battle-axe block needs to meet the 450m2 minimum area and 12 metre minimum width requirements for CDC. The access handle (the strip of land connecting to the street) is typically excluded from the lot area calculation, and the width is measured at the building line rather than at the narrowest point. Some battle-axe blocks qualify, others don’t. The shape of the lot and where the building can sit within it both matter. Have your builder check the specific geometry before you get too far into design.
Does a granny flat need its own water meter?
Not necessarily. Under the Lake Macquarie DCP 2014, Part 9, utility infrastructure (water, sewer, gas) for a secondary dwelling can be shared with or independent from the principal dwelling. If shared services are proposed, the design needs to comply with the relevant Australian Standards for shared metering. Hunter Water’s requirements apply and, in some cases, their concurrence is needed. A separate meter is often simpler from a tenancy management perspective if you’re planning to rent the flat out, but it’s not mandated. Worth confirming with your builder and Hunter Water early if it affects your design.
Can I convert my garage into a granny flat?
Yes, but it still requires development consent. Converting an existing structure into a secondary dwelling, including a garage, a studio, a shed or part of the main house, is treated as a change of use and requires either a CDC or DA. The converted space needs to meet all the same requirements as a new secondary dwelling, including BASIX, setbacks, and habitability standards under the National Construction Code.
How long does a granny flat take to build in Newcastle?
From initial enquiry to handover, most CDC granny flat projects in Newcastle and Lake Macquarie run 14 to 20 weeks. That includes the design and documentation phase (typically 4 to 6 weeks), CDC approval (10 to 20 business days), and the build itself (8 to 12 weeks for a standard detached flat). DA projects take longer given the approval timeline. Mine subsidence approval, if required, should be factored in alongside the CDC or DA process.
If you’re thinking about building a granny flat on your Newcastle or Lake Macquarie property and want to understand what applies to your specific block, fill in our enquiry form and we’ll be in touch.
