Key Takeaways
• The two main ways to fund a granny flat are borrowing against the equity in your home, or a construction loan with progress payments.
• In NSW, a secondary dwelling up to 60 square metres on a lot of 450 square metres or more can usually be approved as complying development in a couple of weeks, without a full DA.
• A granny flat can affect the tax treatment of your home, so it's worth a conversation with your accountant before you commit, not after.
As a broker, granny flats come up in conversation far more often than they used to. Sometimes it's parents wanting somewhere for adult kids who can't yet afford to move out. Sometimes it's the reverse - making room for an ageing parent while keeping everyone's independence. And increasingly it's simply about income: a well-built granny flat in the right suburb can rent for hundreds of dollars a week. Whatever the reason, the question I'm asked is usually the same one: how do I actually pay for it?
What counts as a granny flat, and what do the rules say?
In NSW, the technical term is a 'secondary dwelling' - a self-contained small home on the same lot as your main house. The rules are more generous than many people expect;
If your block is at least 450 square metres and in a residential zone (large-lot R5 zoning is the main exception), and the flat is no bigger than 60 square metres (or larger where your council's own rules allow), you can usually get approval as 'complying development' - a fast-track approval issued by a private certifier, typically within a couple of weeks, without a full development application to council. However there are exceptions to this, including heritage, flood and bushfire affected land, so the first step is always checking what applies to your block. Your builder or certifier can usually tell you quickly.
One note for readers outside NSW: the planning rules above are NSW's. Every state and territory has its own version, and while most have moved in the same direction in recent years, the size limits, approval pathways and rules around renting the flat out all differ. The finance side works much the same wherever you are though, and I arrange lending for clients right across Australia, so if your property is interstate the conversation is exactly the same.
What does a granny flat actually cost?
It varies more than the advertising suggests. Prefabricated and kit options start under $100,000, but for a fully built, council-compliant two-bedroom granny flat in Sydney, most people I see end up somewhere between $120,000 and $200,000 once site costs, connections and fit-out are included. Sloping blocks, drainage and access all move the number. Whatever quote you're working from, build in a buffer - in my experience the final figure is rarely under the first estimate.
Option one - borrowing against your equity
For most homeowners this is the simplest path. If your home is worth substantially more than you owe on it, you can refinance or top up your existing loan and draw on that equity to fund the build. So if your equity position is good, this route is usually the cheapest and cleanest.
Option two - a construction loan
If you don't have sufficient equity to draw on without incurring lender's mortgage insurance a construction loan is the other main route; the lender releases funds in stages as the build progresses - slab, frame, lock-up, completion - and you only pay interest on what's been drawn. The trade-off is a little more paperwork is required; lenders will want a fixed-price building contract and plans before they approve anything.
The things people forget to think about
A few items that come up after the build more often than before it. Rental income from a granny flat is taxable, and renting out part of your property can affect the capital gains tax treatment of your home when you eventually sell - the family home is normally exempt, but that exemption can be partly lost where part of the property earns income. However the rules here depend entirely on your circumstances, so this is a conversation to have with your accountant before you commit. It's also worth telling your insurer, checking whether your rates change, and being realistic about what it's like sharing your backyard with a tenant.
Where to start
The order I suggest to clients is simple: check what your block allows, get a realistic build estimate, and then find out what your borrowing position actually is before you fall in love with a design. That last step is where I can help. With more than 30 lenders on my panel, I can tell you which ones handle granny flat builds well, and whether equity release or a construction loan suits your situation better. If you're thinking about a granny flat - for family or for income - book a chat and we'll run the numbers together. My service is free.
FAQ
Q: How much can I borrow for a granny flat?
It depends mostly on the equity in your existing home and your income. A broker can calculate your position across multiple lenders before you apply anywhere.
Q: Do I need council approval to build a granny flat in NSW?
Usually not a full development application. If your lot is 450 square metres or more and the flat is under 60 square metres, most builds qualify as complying development and can be approved by a private certifier in a couple of weeks. Heritage, flood and bushfire affected land are the main exceptions.
Q: Does a granny flat add value to my property?
Generally yes, though rarely dollar-for-dollar what you spend, and it varies by suburb. In areas with strong rental demand the income stream itself is often the bigger financial benefit. A local agent can give you a feel for what buyers in your area pay for a property with a second dwelling.
