About Granny Flat Check

What this site does

Granny Flat Check answers two questions for an Australian block: can you build a granny flat, and how big. Type an address and it loads the lot boundary, zone and overlays from government land data, then places a granny flat in the backyard in 3D. The cost and rent calculators turn that into numbers.

Where the data comes from

• Lots, zones and overlays: Vicmap (State of Victoria, Department of Transport and Planning), NSW Spatial Services and NSW Planning, and Queensland and Brisbane City Council open data.
• Rules: state planning and building sources, linked on each page, including Planning Victoria’s small second dwelling rules and the Victorian building regulator’s fact sheet.
• Prices: builders’ published package prices for 60 m² designs in each city, turned into all-in figures that include GST, design, permits, connections and basic landscaping, plus the site extras listed on the site costs page. Each price guide shows the date it was last checked.
• Tax: ATO and State Revenue Office guidance, summarised on the tax page.

How we keep it consistent

Every price on the site comes from the same table, so the calculator, the city guides, the FAQ and this page always show the same numbers. When a price changes, it changes everywhere at once and the checked date moves.

What it isn’t

It is general information and a concept, not a design, an approval, a quote or tax advice. Check your plans with your council, a registered building surveyor or certifier, and your accountant before you build.