Planning Rules, CDC Requirements and Common Site Restrictions
Published: September 2026
Author: Adam Murphy – Principal Building Designer, ANS Design
Category: Residential Building Design | NSW Planning & Development | Secondary Dwellings
Understanding whether your NSW property is suitable for a secondary dwelling
Building a granny flat can be an effective way to make better use of an existing residential property.
Whether it is intended to provide independent accommodation for family members, additional rental income or a more flexible living arrangement, a secondary dwelling can create opportunities without requiring the purchase of another property.
However, one of the most common questions homeowners ask is:
Can I actually build a granny flat on my property?
In New South Wales, the answer depends on considerably more than whether there is enough room in the backyard.
Your property’s land area, zoning, frontage, existing buildings, landscaping, drainage, setbacks and fire separation requirements can all influence whether a secondary dwelling is permissible and which approval pathway is available.
A property may appear suitable when viewed from the backyard but have restrictions that prevent the proposed development from being approved as complying development.
Understanding these requirements before commissioning detailed building drawings or purchasing a prefabricated granny flat can help avoid unnecessary expenses, redesigns and approval delays.
At ANS Design, preliminary planning and site assessments form an important part of developing practical residential design solutions.
1. What is considered a granny flat in NSW?
Under NSW planning legislation, a granny flat is generally referred to as a secondary dwelling.
A secondary dwelling is a self-contained residence established in conjunction with a principal dwelling on the same parcel of land.
It may be:
- A detached building located behind or beside an existing home.
- An extension attached to the principal dwelling.
- A conversion of part of the existing dwelling.
- A conversion of an existing garage or other suitable structure, subject to approval and building compliance.
A secondary dwelling normally includes its own living, sleeping, cooking and bathroom facilities.
Importantly, a secondary dwelling is not the same as a duplex or dual occupancy.
Under the relevant Housing SEPP provisions, a secondary dwelling remains associated with the principal dwelling and cannot be separately subdivided from it.
Relevant legislation: State Environmental Planning Policy (Housing) 2021 – Chapter 3, Part 1.
The NSW Department of Planning also provides information about secondary dwellings and granny flats.
2. What is the minimum land size for a granny flat in NSW?
One of the most important considerations is the area of the property.
For a new detached or attached secondary dwelling proposed under the Housing SEPP complying development pathway, the minimum lot area is generally:
450 square metres
However, this does not mean that every residential property measuring 450m² or more automatically qualifies for a granny flat.
Other development standards must also be satisfied.
These include lot frontage, site coverage, landscaped area, building height and setbacks.
What if my property is smaller than 450m²?
A property smaller than 450m² will not satisfy the minimum lot area requirement for a detached or attached secondary dwelling under the Housing SEPP CDC pathway.
However, that does not necessarily mean a secondary dwelling is impossible.
A Development Application may be available, depending on the applicable planning controls and the nature of the proposal.
A secondary dwelling wholly contained within an existing principal dwelling may also qualify for a different complying development pathway, provided the specific requirements are satisfied.
This distinction is particularly relevant to homeowners considering converting existing internal accommodation rather than constructing a separate building.
ANS Design planning advice: Do not assume that a property below 450m² has no secondary dwelling potential. The appropriate approval pathway should be investigated before ruling out the development.
For further information on the importance of investigating planning controls before commencing a design, read Adam Murphy’s related article:
Before You Design: NSW Planning Due Diligence, DA and CDC Requirements – ANS Design.
Legislative reference: Housing SEPP 2021, sections 52–54 and Schedule 1.
3. Does my property’s frontage affect granny flat approval?
Yes.
Lot width is frequently overlooked during the early planning stages.
Under Schedule 1 of the Housing SEPP, the minimum primary road frontage for a conventional lot varies according to its area.
| Lot area | Minimum frontage at the building line |
|---|---|
| 450m²–900m² | 12 metres |
| More than 900m²–1,500m² | 15 metres |
| More than 1,500m² | 18 metres |
Different requirements apply to battle-axe lots.
For example, the CDC provisions require a battle-axe lot to have an access laneway at least 3 metres wide and a site area measuring at least 12 metres by 12 metres, excluding the access laneway.
The battle-axe access handle is also excluded when calculating the lot area for these purposes.
The property must have lawful access to a public road.
A substantial backyard does not automatically compensate for insufficient lot frontage.
A survey and title review can establish whether the property satisfies the relevant frontage and access requirements.
Legislative reference: Housing SEPP 2021 – Schedule 1, section 2.
4. How large can my granny flat be?
For many NSW properties, the maximum floor area of a secondary dwelling is:
60m²
However, the Housing SEPP allows a larger secondary dwelling where another applicable environmental planning instrument permits a greater floor area.
The 60m² figure should therefore be treated as the general standard rather than an absolute limit in every circumstance.
The combined floor area of the principal dwelling and secondary dwelling must also satisfy the applicable requirements.
A well-designed 60m² secondary dwelling can potentially accommodate two bedrooms, a bathroom, kitchen, laundry facilities and an open-plan living area.
The internal arrangement, wall thicknesses, circulation space and relevant floor area definitions must be considered when preparing the design.
Is a two-bedroom granny flat possible within 60m²?
Yes.
A compact two-bedroom secondary dwelling can be designed within this floor area.
However, achieving a suitable outcome requires careful consideration of bedroom dimensions, kitchen and bathroom arrangements, circulation, natural light, ventilation and energy efficiency.
Good design is particularly important when working within a restricted floor area.
What about a smaller granny flat?
Not every homeowner needs the full 60m².
For some properties, a smaller secondary dwelling may be better suited to the available land, budget and intended use.
A compact design may assist in preserving landscaped area and providing a more comfortable relationship between the new and existing buildings.
For an example of how a compact design can accommodate independent living, read:
Legislative reference: Housing SEPP 2021, Schedule 1, section 4.
5. Do I need a CDC or Development Application for a granny flat?
There are two principal approval pathways for secondary dwellings in NSW.
Understanding the difference is essential.
Option 1: Complying Development Certificate (CDC)
A Complying Development Certificate is a combined planning and construction approval available for development that satisfies prescribed legislative requirements.
A CDC can be issued by an appropriately registered certifier or council.
Unlike a conventional Development Application, complying development does not involve a general merit-based assessment of departures from the applicable development standards.
The proposal must satisfy the requirements of the relevant legislation.
For an attached or detached secondary dwelling under the Housing SEPP, this generally includes compliance with the applicable provisions of the Housing SEPP and the Exempt and Complying Development Codes SEPP.
A CDC may provide a more direct approval pathway for a suitable property.
However, eligibility must be established before proceeding.
The NSW Government explains this approval pathway through its Complying Development information service.
What happens if one CDC requirement cannot be satisfied?
If a mandatory requirement is not met and no applicable exception or lawful alternative is available, the proposed development cannot proceed under that particular complying development pathway.
The building design may need to be amended, or a Development Application may need to be considered.
This is why preliminary compliance assessment is an important part of the design process.
Option 2: Development Application (DA)
A Development Application involves a planning assessment by the relevant consent authority, usually the local council.
A DA may be appropriate where a secondary dwelling is permissible but does not satisfy the applicable CDC requirements.
Examples may include:
- A property that does not meet the CDC minimum lot size.
- An insufficient rear setback.
- A site affected by heritage restrictions.
- A design requiring consideration of local planning controls.
- A property with constraints that exclude the relevant complying development pathway.
A DA may allow an appropriately justified proposal to be considered on its planning merits.
However, a DA does not guarantee approval simply because a CDC is unavailable.
The development must still be permissible and satisfy the relevant statutory requirements, with any proposed variations supported by appropriate planning justification.
Depending on the development, a separate Construction Certificate may be required following development consent.
ANS Design provides DA and CDC documentation services across Sydney and NSW, including preliminary design, planning reviews, documentation and consultant coordination.
6. What setbacks apply to a granny flat in NSW?
Setbacks determine the minimum distance a building must be positioned from the property’s boundaries.
They are among the most common reasons a secondary dwelling design requires adjustment.
Under Schedule 1 of the Housing SEPP, the relevant CDC setback requirements vary according to lot area, building height and the boundary concerned.
Side setbacks
For relevant development not exceeding 3.8 metres in height, the minimum side setbacks are generally:
| Lot area | Minimum side setback |
|---|---|
| 450m²–900m² | 900mm |
| More than 900m²–1,500m² | 1.5 metres |
| More than 1,500m² | 2.5 metres |
Additional setback requirements apply where building height exceeds 3.8 metres.
Rear setbacks
The general minimum rear setbacks for development not exceeding 3.8 metres in height are:
| Lot area | Minimum rear setback |
|---|---|
| 450m²–900m² | 3 metres |
| More than 900m²–1,500m² | 5 metres |
| More than 1,500m² | 10 metres |
Additional requirements can apply to taller buildings, corner lots, classified roads and particular site configurations.
The maximum building height under Schedule 1 is generally 8.5 metres, but this does not mean an 8.5-metre secondary dwelling can be constructed using the minimum setbacks shown above.
Building height and setbacks must be assessed together.
These requirements are detailed in Schedule 1 of the Housing SEPP 2021, particularly sections 6, 9 and 10.
7. How close can a granny flat be to the existing house?
This is a particularly important design consideration.
The distance between a principal dwelling and a detached secondary dwelling is not simply a matter of providing enough room for a pathway.
The relationship between the buildings must also satisfy the relevant National Construction Code requirements.
For a typical detached secondary dwelling, this includes consideration of fire separation.
The 1.8-metre fire separation requirement
Under the NCC 2022 Housing Provisions, Part 9.2, an external wall of a Class 1 building and its openings generally require particular fire-resisting construction where the wall is less than:
- 900mm from a relevant allotment boundary; or
- 1.8 metres from another building on the same allotment, subject to the specified exceptions.
This can affect the proposed secondary dwelling as well as the existing principal dwelling.
For example, where a granny flat is positioned close to an existing bedroom or living-room window, the fire separation requirements may influence whether that window can remain in its existing form.
Potential design considerations include fire-resisting external wall construction, protection of openings, alternative window arrangements and reconsideration of the building location.
The appropriate solution depends on the actual building configuration and the relevant NCC provisions.
A 900mm planning setback from the side boundary does not automatically establish adequate fire separation from the existing house.
These are separate requirements and should be assessed independently.
NCC reference: Australian Building Codes Board – NCC 2022 Housing Provisions, Part 9.2: Fire Separation of External Walls.
8. How much private open space must be provided?
A granny flat should not be designed solely around maximising the internal building area.
The remaining outdoor space is equally important.
Under Schedule 1, section 17 of the Housing SEPP, the property must provide more than 24m² of principal private open space.
The relevant area must generally:
- Be directly accessible from and adjacent to a habitable room other than a bedroom.
- Have a width of at least 4 metres.
- Have a gradient no steeper than 1:50.
The principal private open space may be shared between the principal dwelling and secondary dwelling.
It may also take the form of a qualifying balcony or deck.
Why the dimensions matter
Consider a property where the proposed development leaves an outdoor area measuring exactly 3 metres by 8 metres.
Although the area is 24m², it would not satisfy the relevant CDC principal private open space requirements because the specified area must exceed 24m² and have the required width.
This illustrates why simply calculating the amount of vacant land remaining after construction is not sufficient.
The location, dimensions, accessibility and gradient of that space must also be considered.
ANS Design planning advice: Private open space should be considered at the preliminary design stage rather than treated as whatever remains after the granny flat has been positioned.
Legislative reference: Housing SEPP 2021 – Schedule 1, section 17.
9. How much landscaping must remain on the property?
Landscaped area requirements can significantly affect secondary dwelling feasibility.
Under Schedule 1, section 16 of the Housing SEPP, the minimum landscaped area generally depends on the size of the property.
| Lot area | Minimum landscaped area |
|---|---|
| 450m²–600m² | 20% |
| More than 600m²–900m² | 25% |
| More than 900m²–1,500m² | 35% |
| More than 1,500m² | 45% |
At least 50% of the required landscaped area must be located behind the building line to the primary road boundary.
The relevant landscaped area must also satisfy minimum dimensional requirements exceeding 2.5 metres.
Example: An 800m² residential property
Consider a property with a total area of 800m².
The applicable landscaped area requirement would generally be 25%.
This means the completed development would need to retain at least 200m² of qualifying landscaped area.
Of that minimum required area, at least 100m² would need to be positioned behind the building line.
The existing dwelling, granny flat, garage, driveway, paved areas and other site improvements must all be considered when assessing the development.
A property may have enough physical space to accommodate a 60m² granny flat but still fail the relevant landscaping requirements.
This is particularly common where the backyard already contains substantial paving, a swimming pool or other structures.
Legislative reference: Housing SEPP 2021 – Schedule 1, section 16.
10. Maximum site coverage: Why existing buildings matter
Site coverage is another important consideration.
It refers to the proportion of the property occupied by buildings and other relevant structures, calculated according to the applicable legislative definition.
Under Schedule 1 of the Housing SEPP, the maximum site coverage for complying development is generally:
| Lot area | Maximum site coverage |
|---|---|
| 450m²–900m² | 50% |
| More than 900m²–1,500m² | 40% |
| More than 1,500m² | 30% |
Certain structures and building elements are excluded from the calculation under the specific provisions of the SEPP.
Why this matters
Consider a property containing an existing dwelling, detached garage, covered outdoor entertaining area and proposed secondary dwelling.
The proposed development must be assessed against the relevant total site coverage requirement.
The amount of vacant land visible in the backyard is not necessarily the amount that can legally be developed.
In some circumstances, redesigning or removing an existing ancillary structure may assist in achieving compliance, provided the relevant approvals and site requirements are addressed.
Legislative reference: Housing SEPP 2021 – Schedule 1, section 3.
11. Common reasons a property may not qualify for a granny flat CDC
Some of the most significant restrictions are not immediately visible during a basic property inspection.
A preliminary planning assessment should investigate the following matters.
Heritage restrictions
Properties containing heritage items or located within heritage conservation areas may be affected by restrictions on complying development.
A heritage listing does not automatically mean a secondary dwelling can never be constructed.
However, it may mean that a Development Application and appropriate heritage assessment are required.
Bushfire-prone land
Properties located on bushfire-prone land require additional assessment.
The Housing SEPP contains specific bushfire provisions for secondary dwelling complying development.
Some bushfire classifications exclude the CDC pathway, while other circumstances may require additional construction measures and documentation.
The applicable requirements should be checked against the property’s mapped bushfire status and a suitable bushfire assessment.
Further information can be obtained from the NSW Rural Fire Service and the applicable provisions of the Housing SEPP 2021.
Flood-affected properties
Flood planning constraints are particularly important for properties located near waterways, floodplains and low-lying areas.
A property may be affected by flood planning levels, overland flow, flood storage requirements, flood evacuation considerations or restrictions on construction within particular parts of the site.
A flood-affected property is not necessarily ineligible for secondary dwelling development.
However, certain flood constraints can restrict the complying development pathway or require additional design and engineering measures.
The Housing SEPP includes specific provisions addressing complying development on flood control lots.
Sewer mains and drainage infrastructure
This is a particularly important issue for backyard development.
A sewer main may pass through the rear of a residential property in precisely the location where a homeowner intends to construct a granny flat.
Depending on the asset and proposed works, development may require additional assessment, building plan approval, protection measures or engineering.
For properties serviced by Sydney Water, proposed construction near or over relevant assets may need to be referred to a water servicing coordinator.
Importantly, Sydney Water states that qualifying secondary dwellings approved under the Housing SEPP complying development provisions do not require a Section 73 Compliance Certificate, but full building plan approval remains necessary.
The requirements for a particular DA-approved development should be confirmed with Sydney Water and the consent authority. Sydney Water
Further information:
Sydney Water – Building Plan Approvals
Sydney Water – Section 73 Compliance Certificates
Easements and restrictions on title
An easement may restrict where a building can be positioned.
Common examples include easements for drainage, sewerage and services.
Restrictions on title and relevant covenants should also be reviewed.
These matters can affect the development independently of the general planning controls.
Sloping land and excessive earthworks
A relatively flat backyard may accommodate a secondary dwelling with limited site disturbance.
A sloping property can be more complicated.
Depending on the proposed design, earthworks may be required for foundations, retaining walls, access and drainage.
The Housing SEPP imposes limits on excavation and filling under its complying development standards.
Where the proposed earthworks exceed the applicable requirements, the design may require amendment or an alternative approval pathway.
Existing unauthorised structures
A further issue can arise where an existing garage, extension, shed or other structure has been constructed without the appropriate approval.
This is particularly relevant where a homeowner intends to convert that structure into a secondary dwelling.
Existing building status, lawful use, structural adequacy and compliance with applicable building standards must be considered.
A Building Information Certificate should not be confused with development consent or approval to use a building as a dwelling.
For further information on this issue, read:
12. Can I convert my existing garage into a granny flat?
Potentially, yes.
Garage conversions can be an alternative to constructing an entirely new detached building.
However, an existing garage is generally a Class 10a building under the National Construction Code.
A residential secondary dwelling will ordinarily require compliance with the relevant Class 1 building provisions.
Consequently, converting a garage involves considerably more than installing a kitchen, bathroom and internal walls.
The existing building may need to be assessed for structural adequacy, fire separation, ceiling height, natural light, ventilation, damp-proofing, waterproofing, thermal performance, insulation, energy efficiency, drainage and sanitary facilities.
What if the existing garage is very close to the boundary?
A garage located close to a side or rear boundary may have been approved under provisions applicable to a non-habitable building.
Converting that garage into a dwelling can introduce different planning and building requirements.
The fact that an existing garage is lawful does not automatically mean its conversion to residential accommodation can be approved.
In some circumstances, a Development Application may be appropriate.
ANS Design planning advice: Existing garage conversions should be assessed against both the planning controls and NCC requirements before the homeowner commits to the project.
For further information on the sustainability requirements applicable to conversions, refer to:
NSW Planning Portal – Secondary Dwelling BASIX Project Classification.
13. Do I need additional parking for a granny flat?
Under Schedule 1 of the Housing SEPP, the construction of a secondary dwelling does not itself require the provision of additional parking spaces.
However, this should not be interpreted as permission to remove existing approved parking without considering other applicable requirements.
Where a garage or carport is being converted, the impact on existing parking arrangements must be assessed.
For a Development Application, the relevant provisions of the Housing SEPP and any applicable local planning requirements should also be considered.
Parking should form part of the preliminary assessment where the proposed secondary dwelling affects existing vehicle accommodation.
14. Are BASIX and NatHERS required for a granny flat?
Secondary dwellings must satisfy applicable building sustainability requirements.
The NSW Building Sustainability Index, commonly known as BASIX, addresses matters such as water efficiency, energy consumption and thermal performance.
Depending on the project, this may influence building orientation, window sizes, glazing, insulation, shading, solar access, ventilation and water efficiency measures.
A NatHERS thermal assessment may form part of the applicable compliance pathway.
An important distinction applies to garage conversions.
In its December 2025 BASIX guidance, the NSW Department of Planning clarified that converting existing non-habitable space, such as a garage, into a new secondary dwelling is generally assessed under the BASIX standards for a new dwelling rather than as a conventional alteration and addition.
This can significantly influence the design and construction requirements of an older building.
Further information:
NSW Planning Portal – BASIX Requirements
NSW Planning Portal – December 2025 BASIX Secondary Dwelling Clarification
ANS Design also provides BASIX and NatHERS coordination as part of its residential design services.
15. Can I build a granny flat and the main house at the same time?
Yes, this may be possible.
The Housing SEPP includes provisions for development involving a principal dwelling and secondary dwelling being constructed together.
The principal dwelling and secondary dwelling must satisfy their respective applicable requirements.
This can provide an opportunity for homeowners constructing a new residence to consider secondary dwelling accommodation at the beginning of the project.
Planning both dwellings together can assist with coordinated building placement, drainage, landscaping, access and outdoor living arrangements.
It may also avoid unnecessary alterations to the site after the principal dwelling has been constructed.
A combined proposal should be assessed against the appropriate approval pathway from the outset.
Further information is available under section 55 of the Housing SEPP 2021.
16. Does a prefabricated granny flat avoid the planning approval requirements?
No.
Prefabricated and modular construction can provide an alternative method of delivering a secondary dwelling.
However, the method of construction does not generally remove the need for applicable planning and building approvals.
A prefabricated granny flat must still be assessed against the relevant requirements for the property.
These may include:
- Land zoning and development permissibility.
- CDC or DA requirements.
- Boundary setbacks.
- Building height.
- Site coverage and landscaping.
- NCC compliance.
- Structural engineering and foundations.
- BASIX requirements.
- Stormwater and sewer connections.
A prefabricated building advertised as being suitable for NSW complying development should not be assumed to qualify on every residential site.
The proposed dwelling and the actual property must be assessed together.
17. What should I do before spending money on granny flat construction?
The first step should be establishing what can actually be approved on the property.
Before commissioning final construction documentation or entering into a building contract, it is worth obtaining a preliminary feasibility assessment.
At ANS Design, the preliminary investigation of a proposed secondary dwelling may involve reviewing the property’s planning controls and available site information.
This can include:
Property and planning review
Establishing the land area, zoning, relevant planning restrictions and potential CDC eligibility.
Existing building assessment
Considering the location of the principal dwelling, garages, sheds and other existing structures.
Site layout and design investigation
Determining whether the proposed secondary dwelling can be accommodated while satisfying the relevant setbacks, site coverage, landscaping and private open space requirements.
Preliminary NCC considerations
Identifying potential fire separation and building compliance issues.
Services and drainage review
Considering available information about stormwater, sewer infrastructure and other relevant constraints.
Approval pathway advice
Identifying whether the proposal appears suitable for a CDC or whether a Development Application should be investigated.
A preliminary review cannot replace the final assessments required by the certifier, council or relevant consultants, but it can help identify significant constraints before substantial design and construction expenditure is committed.
For a more detailed explanation of this approach, read:
NSW Planning Due Diligence: What Homeowners Should Check Before Designing – Adam Murphy, ANS Design.
18. How can I check whether my NSW property has granny flat potential?
A useful starting point is obtaining a current Section 10.7 Planning Certificate.
The certificate can identify important planning information affecting the property.
This may include land zoning, applicable planning controls and relevant hazard or restriction information.
A Section 10.7(2) and (5) certificate can provide additional information beyond the standard planning certificate.
Homeowners can also review property information through the NSW Planning Portal Spatial Viewer.
However, mapping information alone does not establish that a secondary dwelling can be approved.
A detailed assessment should consider the actual property dimensions, existing buildings, relevant legislation and intended development.
Useful NSW Government property investigation links
NSW Planning Portal – Spatial Viewer
NSW Planning Portal – Section 10.7 Planning Certificate Service
Service NSW – Apply for a Planning Certificate
Frequently Asked Questions
Can I build a granny flat on a 450m² block?
Potentially, yes. A 450m² property may satisfy the minimum lot area for a detached or attached secondary dwelling under the Housing SEPP CDC pathway. However, frontage, setbacks, landscaping, site coverage and other applicable requirements must also be satisfied.
Can I build a granny flat on a 400m² block?
A new detached or attached secondary dwelling on a 400m² property would not satisfy the Housing SEPP’s 450m² minimum requirement for that CDC pathway. However, a Development Application or a qualifying internal conversion may be worth investigating.
Can I build a granny flat on a battle-axe block?
Potentially. Different access and dimensional requirements apply. The access laneway is excluded when calculating the relevant lot area, and the site must satisfy the applicable Housing SEPP provisions.
Does a granny flat need its own driveway?
Not necessarily. The Housing SEPP CDC provisions do not generally require an additional parking space solely because a secondary dwelling is being constructed. Existing parking, access and site arrangements must nevertheless be assessed.
Can I build a granny flat against the rear fence?
A new detached secondary dwelling must satisfy the applicable planning setbacks unless a lawful alternative approval pathway or exception applies.
The general CDC rear setback for a 450m²–900m² property is 3 metres for a building not exceeding 3.8 metres in height.
Can I build a granny flat if my property is flood affected?
Possibly. The nature of the flood constraint and the applicable development standards will determine whether complying development is available or whether a DA is required.
Can I build a granny flat if my property is heritage listed?
A secondary dwelling may still be possible, but heritage restrictions can prevent the relevant CDC pathway and require a Development Application and heritage assessment.
Can I rent out my granny flat?
A lawfully approved secondary dwelling can generally be used as independent residential accommodation, including rental accommodation, subject to applicable consent conditions, legal requirements and any relevant restrictions affecting the property.
Can I sell my granny flat separately?
A secondary dwelling developed under the Housing SEPP is not a separately subdividable dwelling.
If separate ownership is the objective, a different form of residential development and subdivision feasibility should be investigated.
Final thoughts: The right design starts with understanding the property
A secondary dwelling can provide a valuable opportunity to increase the functionality of an existing residential property.
However, successful development requires more than choosing a suitable floor plan.
The relationship between the existing dwelling, proposed secondary dwelling, property boundaries, private open space, landscaping, services and building regulations must all be considered.
A well-designed secondary dwelling should respond to the actual property rather than attempting to force a predetermined building design onto a site that may not accommodate it.
For some homeowners, a straightforward detached granny flat may be achievable under complying development.
For others, an attached secondary dwelling, garage conversion or Development Application may provide an alternative worth investigating.
The most important first step is establishing what the property can accommodate and which approval pathway is appropriate.
Understanding these matters early can help reduce unnecessary redesign, improve project planning and provide greater confidence before construction expenditure begins.
Planning a Granny Flat or Secondary Dwelling in NSW?
ANS Design – Building Design, Planning & Development Solutions
Whether you are considering a detached granny flat, attached secondary dwelling or conversion of an existing garage, ANS Design can assist with investigating your property’s development potential.
Led by Adam Murphy, Principal Building Designer, ANS Design provides practical residential building design and planning advice tailored to the requirements of individual properties.
Established in 2002, ANS Design works with homeowners, builders, property owners and developers across Sydney and NSW.
Our services include:
- Preliminary granny flat and secondary dwelling feasibility assessments.
- Residential building design and documentation.
- CDC eligibility and planning compliance reviews.
- Development Application documentation.
- Garage conversions and alterations to existing dwellings.
- NCC-related design considerations.
- BASIX and consultant coordination.
- Council and certifier documentation and correspondence.
You can explore examples of our residential building design work, including secondary dwellings, on the ANS Design Projects page.
For further information about the services we provide, visit our Building Design Services page.
Considering a granny flat but unsure whether your property qualifies?
Contact Adam Murphy at ANS Design to discuss your proposed development and the appropriate next steps.
ANS DESIGN
Building Design, Planning & Development Solutions
Principal Building Designer: Adam Murphy
Telephone: 0412 508 336
Email: info@ansdesign.com.au
Website: www.ansdesign.com.au
Enquiries: Contact ANS Design
Service areas: Sydney, Greater Sydney and selected regional NSW locations.
About the Author
Adam Murphy – Principal Building Designer, ANS Design
Adam Murphy is the Principal Building Designer at ANS Design, a Sydney-based building design practice established in 2002.
Adam works closely with homeowners, builders and property owners across NSW, providing practical residential building design, planning advice and development documentation.
His work includes new homes, alterations and additions, secondary dwellings, garage conversions, DA and CDC documentation, and assistance with residential planning and compliance matters.
With more than 20 years of experience, Adam focuses on understanding each property’s requirements and developing practical design solutions suited to the site, the client’s objectives and the relevant approval pathway.
Learn more about Adam Murphy and ANS Design:
About Adam Murphy – Principal Building Designer, ANS Design
Disclaimer: This article provides general information about secondary dwelling planning and building requirements in NSW as at September 2026. Requirements may change and individual properties may be subject to additional planning, building, environmental, title or infrastructure restrictions. The information should not be relied upon as confirmation of development eligibility or approval. Project-specific planning, building and consultant assessments should be undertaken before proceeding.
Adam Murphy
Principal Building Designer
ANS Design
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