Develpr guide

Granny Flats in NSW: What Property Owners Need to Know

Granny flats are one of the most common ways NSW homeowners add value or house family without moving. The rules are more consistent than most planning topics, which is part of the appeal.

This guide explains what a secondary dwelling is, what generally makes a block suitable and what needs checking before you commit to a design.

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The short answer

In most residential zones in NSW, a secondary dwelling, commonly called a granny flat, can be built on the same lot as an existing house. State planning policy sets a common framework, including a maximum internal floor area of 60 square metres for a secondary dwelling and a minimum lot size for the Complying Development pathway.

Suitability comes down to lot size and shape, the space left after the existing house, setbacks, private open space, access and any site constraints such as heritage, flooding, bushfire or easements. The controls applying to your individual property still need to be checked, since councils can vary the detail and some sites are excluded from the fast pathway.

What is a granny flat?

In planning terms it is a secondary dwelling. A self contained home with its own kitchen, bathroom and living space, on the same lot and the same title as the principal dwelling.

It can be attached to the house, built as a separate structure in the rear yard, or in some cases created within the existing building. What it cannot be, without a separate approval process, is a second lot. The land stays as one title.

That single title point is the main difference between a granny flat and a dual occupancy that is later subdivided.

Could this work on my property?

Most of the assessment is about whether the granny flat and the existing house can both sit comfortably on the lot.

Zoning: Secondary dwellings are permitted in most residential zones where dwelling houses are permitted, subject to the applicable policy and local plan.
Lot size: The Complying Development pathway for secondary dwellings applies a minimum lot size. Smaller lots may still be possible through a DA, depending on the council.
Floor area: A secondary dwelling is capped at 60 square metres of internal floor area under state policy, which shapes the whole design.
Space behind the house: Rear yard depth is usually the deciding factor for a detached granny flat, once setbacks and open space are taken out.
Private open space: Both dwellings need usable open space, so the yard cannot be entirely built out.
Access: Pedestrian access to the secondary dwelling needs to work sensibly, and some councils prefer separate access down the side of the house.
Parking and driveways: Parking requirements vary. Existing driveway and garage arrangements often influence where the granny flat can sit.
Trees and landscaping: Significant trees, deep soil requirements and landscaping controls can reduce the buildable area at the rear.

What should be checked first?

The zone and whether a secondary dwelling is permitted on the property.
Lot size, width and the usable rear yard once setbacks and open space are deducted.
Whether the site is excluded from Complying Development by heritage, flood, bushfire or other mapping.
The location of sewer mains and easements, which frequently sit across rear yards.
Existing site levels and drainage, since stormwater disposal can be the hidden cost.
Council parking and access expectations for a second dwelling.
Any covenant or restriction on the title limiting additional buildings.

Will I need a DA or CDC?

Complying Development

A Complying Development Certificate is a fast, standards based approval. It is only available where the proposal meets every applicable requirement and the site is not excluded. Miss one standard and the pathway is gone.

Development Application

A DA is lodged with the council and assessed on its merits, with notification to neighbours in most cases. It takes longer, but it allows design that does not fit neatly inside the codes.

Many granny flats are delivered as Complying Development because the standards are clear and the design is small. That requires the lot, the setbacks, the floor area and the site to satisfy every relevant requirement.

Where a site is excluded, or where the design needs a variation, a Development Application to the council is the alternative. Councils regularly approve secondary dwellings through a DA, so a failed CDC test is not the end of the project.

What can affect the opportunity?

Small or irregular lots

Once setbacks and open space are applied, some yards simply cannot fit a 60 square metre building.

Heritage

Heritage items and conservation areas are commonly excluded from the fast pathway and need careful design.

Flooding

Flood affected rear yards can require raised floors or rule out a habitable structure in part of the site.

Bushfire

Bushfire prone land brings construction standards and setback requirements to managed land.

Sewer and easements

Building over a main is generally avoided, and relocation or a build over approval adds cost and time.

Trees

Protected trees and their root zones often dictate where a detached dwelling can go.

Slope

Steep rear yards raise retaining, access and drainage costs quickly.

Thinking about a granny flat in one of these areas?

What should I do next?

Start with the property, not the floor plan. Confirm the zone, the lot size, the constraints and the realistic building area at the rear.

If it stacks up, a Registered Planner can review the site against the applicable controls and confirm which approval pathway suits, before you pay for a full design package.

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Common questions

Can I build a granny flat on my property in NSW?

In most residential zones a secondary dwelling is permitted on the same lot as a house, provided the lot and the design meet the applicable requirements. The practical test is whether the yard can take another building once setbacks, private open space, landscaping and access are accounted for. Heritage, flood and bushfire mapping can also affect the answer for a specific address.

How big can a granny flat be in NSW?

State policy caps a secondary dwelling at 60 square metres of internal floor area. Some elements such as certain verandahs, carports and storage may be treated differently depending on the pathway and the council's controls. The cap is on internal living area, so good design matters more than size. Site coverage and open space requirements can further limit the footprint.

What size block do I need for a granny flat?

The Complying Development pathway for secondary dwellings applies a minimum lot size, which is why 450 square metres is often quoted. Smaller lots are not automatically ruled out, since a Development Application can be assessed on merit by the council. The more relevant question is usually how much usable rear yard remains after the existing house, setbacks and open space.

Do I need council approval for a granny flat?

You need an approval, but not always from the council. If the proposal satisfies every requirement of the relevant code and the site is not excluded, a private certifier or the council can issue a Complying Development Certificate. If it does not, a Development Application is lodged with the council and assessed on its merits. Either way, building certification is required.

Can I rent out a granny flat separately?

Yes, secondary dwellings in NSW can generally be rented to a tenant who is unrelated to the occupants of the main house. The dwelling stays on the same title as the principal dwelling, so it is leased as part of that property rather than sold off separately. Standard tenancy law applies, and the arrangement can have tax and land tax consequences worth checking.

Can a granny flat have separate access?

Usually yes, and separate pedestrian access is often preferred for privacy and amenity. It commonly runs down the side of the existing house to the rear yard. Access needs to be safe, practical and consistent with the relevant code or the council's controls. Separate vehicle access is a bigger ask and depends on frontage width, driveway rules and street conditions.

Can I build a granny flat above a garage?

It is possible in some situations, but it is more complex than a ground level build. Height, setbacks, overlooking of neighbours, structural capacity of the existing garage and access all come into play. Designs like this frequently fall outside the Complying Development standards, so a Development Application is common. It works best where the rear yard is too tight for a detached dwelling.

Can I subdivide a granny flat later?

Not simply because it exists. A secondary dwelling sits on the same title as the main house, and subdividing requires the lot to satisfy the minimum lot size and other subdivision controls for the zone. Owners who want two separate titles usually look at dual occupancy instead, which is designed with subdivision potential in mind where the controls allow it.

Professional review

Get professional advice for your property

Online guides explain the general position. Your property needs to be assessed against the controls that actually apply to it.

Where appropriate, a Registered Planner can review the opportunity and help you understand what may realistically be achievable.

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Related guides

Sources

The planning position described on this page is drawn from the following sources. The requirements that apply depend on the planning controls applying to the individual property, so always confirm the current position for your site.

Planning content reviewed by a Registered Planner. This guide is general information only and is not planning advice for a specific property.

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