Before you draw up plans or price anything, it helps to know what the rules actually let you build. A granny flat, or secondary dwelling in the planning language, comes with a few hard limits. Most of the questions we get from people around Wollongong come back to the same three things: how big it can be, how far it has to sit from the fence, and whether it needs full council approval. Here is what the granny flat rules in NSW actually mean, in plain English.
Granny flat size: the 60m² floor area rule
Under the NSW Housing SEPP, a secondary dwelling can be up to 60 square metres of internal floor area. That is the number most people have heard, and it is a real cap, not a guideline.
A few things that trip people up:
- The 60m² is internal living space. Covered areas like a patio, a carport or a small verandah usually sit outside that figure, within limits, so your usable footprint can feel a bit larger than the number suggests.
- It stays a secondary dwelling. It shares the lot with the main house and cannot be subdivided onto its own title in most cases.
- Bigger is sometimes possible, but not on the fast-track pathway. If you want more than 60m², you are usually looking at a development application rather than the complying development route, which changes the timeline.
Treat 60m² as the working ceiling and design inside it. A well laid out 60m² flat, one or two bedrooms, is plenty for a rental, a teenager, or ageing parents.
Common granny flat sizes in NSW
Almost every granny flat we build lands in one of three sizes inside the 60m² cap: a studio at around 35 to 45 square metres, a one-bedroom at around 50, or a two-bedroom taking the full 60.
- Studio, 35 to 45m². Open-plan living with a kitchenette and a bathroom. The cheapest to build and the simplest to get through approval.
- One-bedroom, around 50m². A separate bedroom and a full bathroom, which is what most tenants and family members are after. 1-bedroom granny flat floor plans goes through what fits.
- Two-bedroom, up to 60m². The most you can build as a secondary dwelling. See 2-bedroom granny flat designs for how the rooms have to give a little.
The cap isn't the only thing setting your size. Setbacks, the shape of the yard and where the sewer runs often mean the biggest flat a block will take is smaller than 60m².
Minimum lot size
The other early filter is your block. In most NSW council areas the land needs to be at least 450 square metres for a granny flat, and it has to be in a residential zone. Plenty of standard Illawarra blocks clear that easily, but battleaxe blocks, older subdivisions and some Southern Highlands lots are worth checking before you get too far.
Zoning matters as much as size. If your block sits in a zone that does not allow secondary dwellings, the 450m² does not help you. That is a quick thing to confirm with your council or a private certifier, and it is worth doing first.
Granny flat setbacks: how far from the boundaries
Granny flat setbacks are the distances the building has to keep from your boundaries, and they depend on your lot size and the pathway you use. As a rough guide under complying development, you are often looking at around 0.9 metres from the side and rear boundaries for a single-storey flat on a typical block, with more room needed on larger lots or for taller builds.
The front is usually governed by the existing house and the street, so a granny flat generally goes behind or beside the main dwelling rather than out front. Drainage easements, sewer lines and big trees can all eat into where the building can actually land, which is why a site check early on saves headaches later.
Do not lock these numbers in from a blog post. Setbacks are the detail council and certifiers look at hardest, so confirm the exact figures for your block before you commit to a layout.
CDC versus DA, in plain English
There are two main ways to get a granny flat approved in NSW.
- Complying development (CDC). If your block and your design tick every box in the complying development rules, a private certifier can approve it without going through full council assessment. It is the faster path, and it is why the 60m², lot size and setback rules matter so much. Miss one, and you fall out of it.
- Development application (DA). This goes to council for assessment. You use it when your block or your plans do not fit the CDC boxes, for example an odd-shaped lot, a heritage overlay, bushfire or flood constraints, or a design that pushes past the standard limits. It takes longer and neighbours can comment, but it gives you room to argue a case.
Neither one is better. It comes down to what your block allows. Part of our job is working out which path is realistic for you before any money goes into design.
What's involved in building a granny flat in NSW?
Four stages: a site check against the rules, design, approval, then the build. Most granny flats around Wollongong and the Illawarra run about six to twelve months from first sketch to handover, and how long a granny flat takes to build breaks down where those months go.
The site check comes first for a reason. Lot size, zone, setbacks, easements and the sewer decide what can go where, and every design decision after that has to live inside those limits. Do it the other way around, fall for a layout, then find the block won't take it, and you pay for drawings twice.
Approval needs a proper document set: a site plan, floor plans, engineering for the footings, and a BASIX certificate for energy and water. Whether you need council approval walks through the CDC and DA paths, and our granny flat builds page covers how we run the design, the approval and the build as one job.
The honest bit
The rules above are the general NSW framework, and they hold true across Wollongong, the Illawarra and the Southern Highlands. Your block is its own story though. Local council controls, easements, overlays and slope can all shift what is possible, so the only way to know for certain is to confirm with your council or a certifier for your specific address.
That is the part we sort out early for clients anyway. We look at the block, work out whether CDC or a DA fits, and put the real limits in front of you before you get attached to a layout that the site will not allow.
Want a hand with this at your place? Get a free quote or call 0434 037 851.