Granny Flat Cost in Australia (2026): What You'll Actually Pay

The range is wide, and for good reason

Granny flats in Australia cost anywhere from $50,000 for a basic kit on a prepared slab to $250,000+ for a fully custom site-built secondary dwelling with high-end finishes. Most people end up somewhere in the $80,000 to $180,000 range for a completed, liveable build including site works and council approvals.

That spread exists because "granny flat" covers everything from a 30 square metre studio to a 60 square metre one-bedroom unit with a full kitchen, bathroom, and laundry. The build method matters too. A prefab granny flat delivered on a truck is a fundamentally different product to a site-built brick veneer addition, and they price accordingly.

Build method makes the biggest difference

Site-built (traditional construction)

A site-built granny flat is constructed on your block by a builder, the same way a house extension would be. This is the most expensive option but gives you the most flexibility on design, materials, and layout.

Expect $1,800 to $3,500 per square metre depending on your state, finishes, and site conditions. A 50 square metre one-bedroom granny flat built on site in Sydney might cost $120,000 to $175,000 all up. The same build in regional NSW or Queensland could be $90,000 to $130,000.

Site-built works best when you want the granny flat to match your existing house, when site access is too tight for crane delivery, or when you need a non-standard layout.

Prefab and modular

A prefab granny flat is factory-built and delivered to your block as a finished or near-finished unit. The factory controls quality, and the on-site work is mostly foundations, connections, and finishing.

Expect $1,500 to $3,000 per square metre including delivery and installation. A 45 square metre prefab granny flat might cost $80,000 to $140,000 delivered and installed, depending on spec and distance from the factory.

The main advantage is speed. A prefab granny flat can be on site and liveable in 8 to 12 weeks from order, compared to 16 to 24 weeks for a site build. The trade-off is less design flexibility, and you need crane access to your block.

Kit homes

A kit granny flat is a set of materials and plans delivered to your site for assembly. You supply the labour, either yourself (owner-builder) or through a local builder.

Kit prices start from $30,000 to $60,000 for materials only. But once you add a slab ($8,000 to $15,000), a builder to assemble it ($20,000 to $50,000), plumbing, electrical, and council fees, the total is usually $70,000 to $120,000.

Kits suit people who have building experience or a trusted local tradesperson. If you are hiring someone to build the kit anyway, compare the total cost against a prefab option where the builder handles everything.

Costs outside the build price

These line items sit outside most builder quotes and catch people off guard:

Council and approval fees: $2,000 to $8,000 depending on whether you go through complying development (faster, cheaper) or a full DA. In NSW, complying development for a secondary dwelling under 60 square metres is usually the cheaper path.

Site preparation: $5,000 to $25,000. This covers demolition of existing structures, tree removal, levelling, and excavation. A flat suburban block with good access might need $5,000 of prep. A sloping block with poor access could need $20,000+.

Slab or foundations: $8,000 to $20,000 depending on size, soil conditions, and whether you need engineered footings.

Service connections: $5,000 to $15,000 for water, sewer, electrical, and stormwater. If you are connecting to existing house services (common in suburban granny flats), this is cheaper. Running new connections from the street boundary costs more.

Landscaping and fencing: $3,000 to $10,000. Often forgotten in the budget but usually required by council, especially for privacy screening between the main house and the granny flat.

On a straightforward suburban block in Sydney with existing services, total ancillary costs might be $20,000 to $40,000. On a difficult site, they can easily exceed $50,000.

State-by-state pricing context

NSW has the most granny flats being built, thanks to the Affordable Rental Housing SEPP which streamlined approvals. Competition among builders keeps pricing competitive, especially in Western Sydney and the Central Coast. Expect $100,000 to $180,000 for a standard 1-bed build including site works.

Victoria has fewer granny flat builders and more restrictive planning rules (dependent person's units). Pricing tends to be slightly higher than NSW for comparable builds, partly due to less competition. Expect $110,000 to $200,000.

Queensland handles secondary dwellings at the council level. Pricing is generally lower than Sydney and Melbourne due to lower labour costs and simpler foundation requirements in many areas. Expect $80,000 to $150,000.

WA caps ancillary dwellings at 70 square metres in many council areas, giving slightly more room than the 60 square metre limit common in NSW. Pricing is comparable to Queensland.

How to compare quotes properly

Get three to five quotes, then put them side by side and check:

• Is the price for the build only, or does it include site works, slab, and connections?
• What finishes are included? "Standard" means different things to different builders.
• What is excluded? Get this in writing.
• Does the price include council approval fees and certification?
• What is the warranty period, and what does it cover?

The cheapest quote is almost never the cheapest total cost. A $90,000 quote that excludes slab, connections, and approvals can easily become $130,000 once you add everything.

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FAQ

Is a granny flat a good investment?

In most cases, yes. A granny flat can add $150,000 to $300,000 in property value depending on your area, and it generates rental income of $300 to $600 per week in metropolitan areas. The payback period is typically 3 to 7 years from rental income alone. But returns depend heavily on your location, council rules around renting, and the quality of the build.

How long does it take to build a granny flat?

A prefab granny flat can be delivered and liveable in 8 to 12 weeks from order. A site-built granny flat typically takes 12 to 20 weeks of construction time. Add 4 to 12 weeks for approvals before construction starts. Total timeline from first call to moving in is usually 4 to 8 months.

Do I need council approval for a granny flat?

Yes, in all states. In NSW, secondary dwellings up to 60 square metres on lots over 450 square metres can use the complying development pathway, which is faster than a full DA. Other states have their own provisions. Read our council approval guide for more detail.