Can I Build a Granny Flat on My Perth Block? A Block Suitability Checklist

Since April 2024, Perth homeowners are allowed to build a granny flat on a residential block of any size, as there is no minimum block size requirement for ancillary dwelling units in the State of Western Australia. However, this does not imply that the size of the block is the only consideration. The block should still satisfy the zoning regulations, 70m2 floor space limit, setbacks, open space, services, and access requirements, amongst other local council conditions. This article will walk you through nine steps in assessing your Perth block’s suitability.

First, Understand What a Granny Flat Is Called in WA

According to the WA planning definitions, a granny flat is an ancillary dwelling. An ancillary dwelling refers to a secondary dwelling that is located on the same land where a primary dwelling already exists and can either be attached to or detached to the dwelling.

An ancillary dwelling in Perth is not a separate subdivision that would be sold separately as a lot. Both the primary and ancillary dwelling stay on the same land. The current R-Codes allow ancillary dwellings on group dwellings and strata sites. 

The 9-Point Block Suitability Checklist

The removal of the minimum lot size has opened the door for many more Perth homeowners, but it does not mean every backyard automatically works. If you are wondering, “Can I build a granny flat on my property in Perth?,” these nine checks will help you assess the main requirements.

1. Is Your Block Zoned for Residential Use?

Your granny flat building eligibility starts with confirming that the property’s zoning allows an ancillary dwelling. A regular Perth residential-zoned property is the easiest to begin with, but others like rural zoning or special purpose zoning may require more investigations.

Investigate the zoning and R-code of the property through your local government mapping facility or the relevant WA property data before you pay for your plans. Do not depend only on the appearance of neighbouring properties because two properties next to each other could have different planning controls.

2. Is There Already a Primary Dwelling?

An ancillary dwelling is a secondary dwelling associated with a primary dwelling. The R-Codes define it as a self-contained dwelling on the same site as the primary dwelling. This means a vacant block cannot simply be treated as a site for a granny flat while the main house is absent. 

If you are buying vacant land and planning both buildings, the project needs to be assessed under the applicable planning pathway rather than assuming the ancillary dwelling exemption applies. Before planning the secondary dwelling, it is also important to understand the granny flat size limit that applies under the current WA provisions. If you are comparing a separate granny flat with a home extension in Perth project, the right choice will depend on your available space, intended use and budget. 

3. Can the Granny Flat Stay Within 70m²?

In relation to the standard ancillary pathway, the maximum internal floor area is 70m². According to the current R-Codes, only one ancillary dwelling with a maximum internal floor area of 70 m² is allowed on a site. This rule is applicable to both single houses and grouped dwellings.

The granny flat 70 m2 limit provides enough space for a practical one- or two-bedroom layout, depending on the design. A custom granny flat can make better use of an unusual block while keeping the layout within the applicable floor area limit. What should be taken into consideration in this case is that 70m² relates to the internal floor area. Therefore, your designer should know what is included in the calculation of the proposed internal floor area.

Larger rural or rural-residential properties may fall under different local planning provisions. 

4. Can the Design Meet the Setback Requirements?

The granny flat must fit within the applicable street, side and rear setback controls while also allowing the existing home to remain compliant. The granny flat R-Codes require ancillary dwellings to satisfy relevant design elements.

The main setback considerations can be summarised as follows:

Before moving forward, have your designer test the proposed footprint against the actual dimensions of your block. This is particularly important for narrow lots, battle-axe blocks, corner properties and sites with unusual boundaries.

5. Does the Whole Site Still Have Enough Open Space?

Having a big backyard does not automatically mean that you have enough room to use it. The ancillary dwelling must be able to coordinate itself with the existing house on the plot and any other buildings on the property. There is no single best block size for a granny flat in Perth, because usable space, setbacks and the existing home’s footprint are equally important. 

In accordance with the R-Codes, the ancillary dwelling should not interfere with the ability of the main house to comply with the requirements for site coverage, private open space, planting and tree coverage, and deep-soil areas.

Before planning the ancillary dwelling, think about how much of the lot is already covered by the existing house, garage, driveway, patio, shed and other hardscapes. The remaining area is what your new design has to work around. While granny flat block size in Perth is no longer subject to a minimum requirement, the available usable space still determines what can realistically be built. Get in touch with experienced boutique home builders to balance the granny flat footprint with the existing home’s outdoor areas. 

6. Is Vehicle Access and Parking Sorted?

Under the 2024 reforms related to granny flat site requirements, an ancillary dwelling will generally not require an additional parking bay. But parking requirements can still apply in specified circumstances depending on density and access to public transport.

That does not mean access can be ignored. Your design still needs to address how residents, visitors and tradespeople can safely reach the property.

For a practical block assessment, look at the existing driveway, side access, pedestrian route and any gates or structures that could restrict construction access. A tight access path can also affect construction costs because materials, machinery and equipment may be harder to bring onto the site. Contact experienced granny flat builders in Perth to assess these access constraints early and help plan the construction around the existing property. 

7. Is the Property Affected by Heritage or Other Special Controls?

According to the granny flat rules in WA, some buildings located in Perth will need to consider other planning factors due to heritage, environmental and other specific controls on the site. This may influence what can be built and whether the planning exemption applies in the normal way.

In case your property is located in a heritage or designated area, you need to consult with your local government before assuming that your complying design is enough to avoid planning approval.

This is particularly important for older properties where the existing house, streetscape or surrounding area may be subject to additional requirements.

8. Does Your Local Council Have Additional Requirements?

The state R-Codes provide the broader framework, but your local planning scheme and local policies can still affect individual projects. That is why checking your council’s requirements is an essential part of the block assessment.

Do not assume that information you find for one Perth suburb will apply identically to another. Before finalising a design, confirm your property’s zoning, local planning scheme, setbacks and any relevant local policies with the council responsible for your address.

This step is especially important if you intend to use the granny flat as a rental or short-term accommodation, because separate rules can apply to those uses. Checking the latest granny flat regulations for your local government area is important because additional local requirements may apply. 

9. Can Water, Sewer and Electricity Be Connected?

The last practical consideration is the ease with which the site can be serviced. An independent ancillary dwelling will require appropriate connections for water, wastewater, electricity and other utilities.

In the case of an established suburban block in Perth, services may be readily available. But connecting a new dwelling can still involve additional design and construction work. Long service runs, difficult ground conditions, limited access or the need to upgrade existing infrastructure can increase the budget.

Check where the existing service connections are before deciding where to position the granny flat. Keeping kitchens, bathrooms and other wet areas sensibly positioned can help simplify plumbing and reduce unnecessary service runs. Experienced Perth residential builders can assess the existing service connections and identify potential complications before construction begins. 

If You Ticked All 9, What Happens Next?

If your granny flat meets the relevant deemed-to-comply requirements, you generally do not need separate planning approval. But remember that you will still need a building permit.

• The building permit confirms that the proposed construction meets applicable building requirements and the National Construction Code.
•  If the design falls outside the deemed-to-comply provisions, granny flat approval may be required through the applicable planning pathway.
• Once your site has been assessed, guidance from experts regarding the design and permits process can help you move from initial plans to the required approvals more efficiently. 
• Your overall timeframe will depend on the design, site conditions, builder availability and approval requirements.

Read More: Granny Flat Building Approvals Guide 2026

Can I Rent Out My Perth Granny Flat?

Yes. WA rules allow eligible granny flats to be rented to unrelated tenants, making them useful for both family accommodation and long-term rental income. Short-term rentals such as Airbnb are also possible. But WA requires short-term rental accommodation to be registered, and this applies to ancillary dwellings used for short stays. From 1 January 2025, a property must be registered before it can be advertised or accept bookings, with the registration number displayed in advertisements.

How Much Does a Granny Flat Add to Your Perth Property Value?

A well-designed granny flat can potentially increase a Perth property’s value by up to 30%, although the actual uplift depends on the suburb, design, privacy, functionality and buyer demand. The granny flat building cost can vary with the design, site access, ground conditions, finishes and service connections. The average cost to build a granny flat in Perth ranges from $120,000 to $200,000+. To assess the granny flat ROI and whether the project makes financial sense, consider the potential value uplift and rental income against the total project cost, rather than construction costs alone.

FAQs- Can I Build a Granny Flat on My Perth Block?

What are the new granny flat regulations in Western Australia?

Western Australia now allows granny flats to be built on most residential properties without requiring the occupant to be related to the homeowner. A compliant granny flat can generally be up to 70m², provided it meets local planning, building and Residential Design Code (R-Code) requirements. Always check your local council and current WA planning rules before starting your project.

Can I buy a block of land and put a granny flat on it?

Yes, you can build a granny flat on a vacant block in Perth, but the land must have the correct residential zoning and comply with local planning and building requirements. In many cases, the granny flat is approved as an ancillary dwelling to a primary residence, so the overall development plan for the property is important.

What is the average cost to build a 2-bedroom granny flat in Perth?

A 2 bedroom (60 to 80 m²) granny flat in Perth typically costs between $140,000–$195,000, depending on the size, design, site conditions, finishes and approval requirements. Premium custom designs and challenging sites may increase the overall project cost.

What are the requirements for building a granny flat in Perth?

To build a granny flat in Perth, you’ll generally need:

• A residentially zoned property

• Compliance with WA R-Codes and local council planning rules

• Building permit approval

• A maximum floor area of around 70m² (unless local provisions allow otherwise)

• Compliance with setbacks, open space and building standards

A planning assessment is recommended before finalising your design.

What is the average price range for a 2-3 bedroom granny flat in Perth, WA?

The average price range for a 2 bedroom (60 to 80 m²) granny flat in Perth is $140,000–$195,000 and a 3 bedroom (90 to 110 m²) granny flat in Perth is $198,000 to $292,500. Exact & close prices depend on the size, design, site conditions, finishes and approval requirements. Premium custom designs and challenging sites may increase the overall project cost. Get a free quote now!

What are the setback requirements for granny flats in Western Australia?

Granny flat setback requirements in Western Australia vary depending on the property’s zoning and the applicable R-Code. As a general guide, side setbacks are commonly around 1–1.5 metres, while front and rear setbacks depend on the lot layout, street frontage and local council requirements. A site-specific assessment is the best way to confirm the exact setbacks for your property.

Can I build a granny flat on a strata lot in Perth?

Yes, since the April 2024 R-Code reforms. Ancillary dwellings are now permitted on strata and grouped dwelling lots, not just single residential lots. However, you should check whether the strata scheme’s by-laws place any restrictions on additional structures, and confirm your council has no additional requirements for your specific area.

Do I need a car park for my Perth granny flat?

Not always. In most cases, no additional parking bay is required. However, if your property is more than 800m from a train station or more than 250m from a high-frequency bus route, one car space at the granny flat must be provided. Outer Perth suburbs — including parts of Baldivis, Ellenbrook, and Joondalup — often fall into this category.

Read More: A Granny Flat Building Costs in Perth 2026

Conclusion: Is Your Perth Block Suitable for a Granny Flat?

The reforms implemented in April 2024 have scrapped the granny flat minimum lot size requirement that existed before, and now granny flats can be erected on more properties in Perth. But your property must meet the necessary zoning, floor area, setback, open space, access, servicing, and local government standards criteria.

Once all nine criteria have been met, you will be ready for a site assessment and a design of compliant dimensions. Working with experienced granny flat builders in Perth can help you assess the site, develop a compliant design and manage the construction process.  With BODA Building Group, Perth homeowners can assess their lot, plan the design, navigate permits and manage construction. Reach out for a discussion about your site’s suitability and potential project costs.