Will a granny flat fit on your block?
Before you pay a draftsperson or a certifier, find out whether the idea is even feasible. Enter your block, drop in a granny flat, and PlanHome checks it against the NSW rules that decide it: a 60 m² floor area cap, a 450 m² minimum lot, boundary setbacks and site coverage. It is free, and nothing is sent anywhere.
The NSW rules that decide it
A secondary dwelling in NSW is governed by the state Housing SEPP, so the headline caps apply no matter which council your block sits in. That is what makes a granny flat one of the few builds you can sensibly check yourself.
| Requirement | Figure | Notes |
|---|---|---|
| Minimum lot sizestate rule | 450 m² | Smaller lots cannot take a secondary dwelling as complying development. |
| Maximum floor areastate rule | 60 m² | Internal floor area of the granny flat, excluding the main house. |
| One per lotstate rule | 1 dwelling | A single secondary dwelling in addition to the principal home. |
| Side / rear setback | 0.9 m (typical) | Common minimum for a single-storey dwelling; varies with lot width and wall height. |
| Storeys | Single storey | Most complying secondary dwellings are single storey. |
| Private open space | 24 m² (typical) | A usable outdoor area is generally required; the figure varies by council. |
The two caps marked state rule are fixed. Setbacks and open space carry council and lot-width nuance, so PlanHome shows the common figures and lets you edit them to match your own block.
How the check works
Enter your block
Type your lot as width by depth, or draw an irregular boundary. The block appears to scale straight away.
Place the granny flat
Drop in a secondary dwelling and reshape it. The green shading shows the area your setbacks actually leave you to build in.
Read the check
Every rule shows a tick or a cross against your design: floor area, lot size, setbacks and coverage. Change the plan and the checks move with it.
Common questions
- How big can a granny flat be in NSW?
- Under the NSW Housing SEPP a secondary dwelling has a maximum internal floor area of 60 m², and this cap is set at state level so it applies regardless of which council you are in. Some councils permit a larger secondary dwelling through a development application, but 60 m² is the figure for complying development.
- What is the minimum lot size for a granny flat in NSW?
- 450 m². A block smaller than this cannot take a secondary dwelling as complying development. PlanHome checks your lot area against this the moment you enter your block, before you draw anything.
- Do I need council approval for a granny flat?
- If the design meets every relevant standard it can be approved as complying development by a registered private certifier, without a full development application. If it breaks any standard, it needs a development application to the council instead. A feasibility check like this one tells you which path you are on before you pay anyone.
- What setbacks does a granny flat need?
- A common minimum side and rear setback for a single-storey secondary dwelling is 0.9 m, but the exact figure varies with your lot width and the height of the wall. PlanHome measures the distance from your design to each boundary so you can see where you stand, and every setback figure is editable to match your own requirements.
- Is this an official approval?
- No. PlanHome is a feasibility and design tool. It shows whether your idea fits the headline rules so you can decide whether it is worth taking further, and it produces a clear drawing to hand to a draftsperson, certifier or builder. The formal assessment is always done by a registered certifier or your council.
Check your block in a few minutes
Start with your lot dimensions. You will see whether a 60 m² granny flat fits inside your setbacks before you commit a cent to a design.
Check your block freePlanHome is a design and feasibility tool, not a planning approval. Figures are a guide to help you decide whether to proceed. Confirm the rules for your block with your council or a registered certifier before you rely on them.