A granny flat, or a secondary dwelling to use the proper term, is one of the most popular ways to get more from a block in NSW. The rules are more generous than a lot of people expect, but there's a right way to go about it. This guide runs through the rules and the approval process in plain terms, so you know what's involved before you start. The Ovas Build team builds granny flats across Wollongong, the Illawarra and the Southern Highlands, and we handle the whole process for you.
The NSW rules in brief
Granny flats in NSW are governed by a state housing policy that sets out when and how you can add a secondary dwelling. The headline rules most blocks come down to are:
- One secondary dwelling per lot, in addition to the main house.
- A minimum block size, generally around 450 square metres for the complying development path.
- A maximum internal living area of 60 square metres, with covered outdoor areas counted separately.
- Setbacks from the boundaries, which depend on the block size and the zone.
- It stays on the same title as the main house and isn't subdivided off under the standard rules.
These are the broad strokes. The detail depends on your zone, your council and the specifics of your block, which is why the first real step is always checking your site against the rules rather than assuming.
CDC or DA: the two approval paths
There are two ways to get a granny flat approved in NSW, and which one you're on shapes your timeline and a chunk of your cost.
Complying Development Certificate (CDC). This is the faster path. If your block and your design tick every box in the state policy, a private certifier can approve it without it going to a full council assessment. It's often signed off in around 20 days once the documents are complete, and it's far more predictable because the rules are set out clearly. Most straightforward granny flats go this way.
Development Application (DA). If your site doesn't fit the complying development rules, an odd lot size, heritage, flood, bushfire or environmental constraints, then it goes as a DA through your council. A DA is assessed on its merits, takes longer, and usually needs more reports and fees. It's not a dead end, it's just a different road, and plenty of good granny flats are built this way.
We explain the approval side in more depth in our guide to granny flat council approval in NSW. The key thing is to work out which path you're on early, because it affects everything that follows.
What a good local builder handles
The reason people find granny flats stressful is that they involve a designer, an engineer, a certifier and a builder, plus the wet trades, all of whom have to line up in the right order. A good local builder takes that off your plate by running the lot:
- Design that suits your block and complies with the rules.
- Engineering, including footings worked out for your slope and soil.
- The approval, whether that's a CDC or a DA, managed for you.
- The build, from site works through to handover, with the trades coordinated.
- A fixed-price proposal so you know the number before you commit.
That's how we work. You get one point of contact from the first site visit to the day we hand over, instead of chasing separate people and hoping they talk to each other. Being local matters here too, because we know how the Illawarra blocks behave, how the councils down here assess things, and what the coast does to a building over time.
Built for the conditions
A granny flat near the coast needs coastal-grade materials and fixings, proper flashing and ventilation, and footings that suit a block that often slopes. We build for those conditions as standard rather than treating them as extras. For a sense of the budget, see our granny flat cost guide, and for the layout options, our granny flat designs page.
If you're thinking about a granny flat, the best first step is a chat about your block and which path it's likely to take. Have a read of how we run the whole build, then call us on 0434 037 851 or use the contact page for a free quote.
Common questions
- What's the minimum block size for a granny flat in NSW?
- Under the state housing policy, a block generally needs to be at least 450 square metres to add a secondary dwelling through the complying development path. Smaller or unusually shaped blocks may still be possible through a DA, depending on the council. The first step is checking your block against the rules, which we do before anything else.
- How big can the granny flat be?
- A secondary dwelling can have up to 60 square metres of internal living area under the complying development rules. Covered patios, decks and carports sit outside that figure within their own limits, so the usable footprint is often a bit larger than 60 metres once you count the outdoor areas.
- Can I build a granny flat to rent out?
- Yes. A compliant secondary dwelling in NSW can be occupied by a separate household, which is why so many are built for rental income. It has to stay on the same lot as the main house and can't be subdivided off under the standard rules, but it can be tenanted separately.
- How long does approval take?
- A Complying Development Certificate is the faster path, often signed off in around 20 days by a private certifier once the design and documents are complete. A DA through council takes longer and varies a lot by council and by how complex the site is. We manage whichever path your block needs.