What we do
Builders, lenders and agents publish granny flat figures to sell a build, a loan or a listing. We publish ours so owners can check them. Each page states what our analysis found and when, and the methodology page lists every input with its source and date.
Our own work on the site includes: a cost model by state, size, finish, method and site; rent medians we computed from 81,668 raw NSW bonds and 8,219 Tasmanian bonds; yield, payback and offset comparisons for 42 areas; and a coded reading of 1,913 public forum posts by owners and tenants.
Who writes it
The site is written and maintained by the Granny Flat Numbers editorial team: cost analysts who build the model, process the government data and check the rules against the source instruments. Pages are reviewed when the underlying data or rules change, and at least every quarter.
Independence
We do not sell builds, take referral fees or accept payment for placement. We link only to government sources. If we ever add advertising, it will be labelled and kept apart from the analysis.
Corrections
Rules and prices change. When a reader, a new data release or a changed rule shows that a number is wrong, we fix it and update the date at the top of the page.
Not advice
The site gives general information. Planning, building, tax and pension decisions depend on your circumstances; check with your council or certifier, an accountant and, for pension questions, Services Australia's Financial Information Service.