What our analysis shows
Analysis by Granny Flat Numbers, data as of 23 October 2026
- Since 2021, the most discussed granny flat topic in the forum threads we read was not cost but services: internet, water meters and addresses (183 of 481 posts).
- Approval questions came second (101 posts), mostly about conflicting advice from certifiers and councils rather than outright refusals.
- Questions about tax, the pension and family arrangements (50 posts) outnumbered questions about builders and prices (18).
What owners asked about most, 2021–2026
- Internet, water and addresses183 posts
- Approval and council101 posts
- Tax, pension and family50 posts
- Unapproved flats43 posts
- Renting and tenants27 posts
- Kits and prefab23 posts
481 posts in 97 Whirlpool threads we read; one topic per thread, our coding.
How much does a granny flat cost in Australia?
A standard 60 m² two-bedroom flat costs $187k–$238k turnkey in our model, from South Australia to the Australian Capital Territory. Site, connections and approval are included. See the analysis.
What is the cheapest way to get a granny flat?
A kit managed by an owner-builder: about $151,500 for 60 m² in Sydney against $220,000 through a builder. Prefab is only slightly cheaper than site-built, and only above about 50 m². See the analysis.
How big can a granny flat be?
60 m² in NSW (unless the council allows more), 80 m² in Victoria's planning rules from 15 October 2026, 70 m² in WA and SA, 90 m² in the ACT, 60 m² in Tasmania, and 45–120 m² in Queensland depending on the council. See the analysis.
Do I need council approval?
Always a building approval. Planning approval depends on the state and design: fast-track routes skip a council assessment in NSW (CDC), Victoria, WA, SA and many Queensland councils, but not in the ACT. See the analysis.
How much rent does a granny flat earn?
From government bond data: $370–$750 a week for two bedrooms across 42 areas. In Sydney a detached one-bedroom dwelling rented for $550, below the $719 for a one-bedroom flat. See the analysis.
How long does a granny flat take to pay for itself?
8.4 to 15.2 years after tax with no loan in our data, fastest in Gold Coast. See the analysis.
Is a granny flat worth it?
After tax and an allowance for the building wearing out, it beat paying down a 6.2% mortgage in most of the areas we tested, but by a thin margin in outer suburbs and regional cities. See the analysis.
Does a granny flat increase land tax?
It can. Victoria taxes the flat's part of the land from 2026; in NSW a 2025 tribunal decision narrowed the exemption for detached rented flats. Thresholds protect many owners without other investment property. See the analysis.
Can I rent my granny flat to anyone?
Yes, in every state and territory. Queensland removed its family-only rule on 26 September 2022. See the analysis.
Can a granny flat be sold separately?
No. It stays on the same title as the main house in every state; subdividing it off needs a different approval as a separate dwelling, where that is allowed at all. See the analysis.
Can my parents pay for a granny flat on my land?
Yes. Centrelink does not treat paying to build a granny flat on someone else's land, in return for a life right to live there, as gifting. Put the arrangement in writing. See the analysis.
How do I get internet to a granny flat?
Either share the main house's connection through a cable or fibre run in conduit, or register the flat's address and apply to NBN for a second location. Lay the conduit during the build. See the analysis.