Granny flats went from a niche strategy a handful of investors ran quietly to something close to a national obsession, to a topic almost nobody wants to touch since the Budget, because the tax position got complicated. Every one of those phases produced a lot of confident content, and not much of it aged well.
This is our update. We wrote about this strategy last year and have been running it in our own portfolio and for clients for longer than that, and enough has changed that a light edit would not have been honest.
The short version: it still works, the planning rules have got easier in most states, the build costs have got harder, and the tax treatment has split into three completely different scenarios depending on when you bought the underlying property. The one you are in depends on when you bought, and that is not something you can change now.
First, what value-add actually means
Value-add is any opportunity to do something to an investment to improve its value, rather than waiting for the market to do it for you. A granny flat is one of those strategies, alongside cosmetic renovation, adding bedrooms, garage and outbuilding conversions and subdivision.
What makes a granny flat distinct is that it is primarily a cash flow play rather than a capital growth play, and the confusion between those two is the mistake we correct most often. If your objective right now is growth, this is generally not the tool that delivers it. If it is to lift the yield on an asset you already own, improve serviceability and spread vacancy risk across two tenancies instead of one, it is a very good tool.
Which is why it gained momentum. The Reserve Bank said it would sit still and then moved quickly, and portfolios that were comfortable when money cost 2% stopped being comfortable at 6%. Investors who were equity rich but serviceability poor needed something to do with equity they could not otherwise deploy. A granny flat puts it to work without needing approval for a whole new purchase.
The lending mechanic behind that is worth understanding. Lenders look at debt-to-income, and a second income on the same title changes that ratio. How much it changes it, and whether a particular lender gives you credit for it, varies widely by lender and by your own position. All lending is subject to lender terms, conditions and eligibility. We do not hold an Australian Credit Licence, so this is a question for your broker.
What changed: the tax position
What follows is our general understanding of the law as at August 2026. It is not tax advice; we are not registered tax agents, and which scenario you fall into depends on facts we do not have. Confirm your own position with your accountant before you commit money.
The 2026 Budget restricted negative gearing on established residential property acquired after 7:30 pm on 12 May 2026, with effect from 1 July 2027. Losses on those properties are quarantined against residential rental income and residential capital gains, carried forward indefinitely, and can no longer be offset against salary or wages. New builds were carved out and keep full deductibility.
Every investor we spoke to asked the same question. Does building a granny flat make my property a new build?
The answer, on everything said so far, is no. In early June 2026 both the Housing Minister and the Secretary to the Treasury said so on the record, in essentially those words: a granny flat built adjacent to an established property is not an eligible new build, and extensions and single-for-single knock-down rebuilds are excluded too.
One important qualification. The binding definition of a new build sits in a regulation that has not been made yet. An exposure draft was released on 4 August 2026, and consultation on it closes on 21 August. So this is the government’s stated position rather than settled law, and it is worth confirming before you rely on it.
Then the part being missed almost everywhere, which changes the answer for a lot of people.
Scenario one: you already owned the property on 12 May 2026. It is grandfathered in its own right and keeps the existing treatment for as long as you hold it. Interest on a construction loan for the granny flat, depreciation on the new structure, capital works deductions, all of it flows into a property that was never in the quarantine bucket. On the current design, the new build test does not need to engage at all. For this group, which is most of the investors who come to us about a granny flat on something they already own, the Budget changed very little. The one thing worth putting to your accountant is how the unfinished regulation treats substantial new construction on a grandfathered property, because nobody can answer that from the outside yet.
Scenario two: you buy an established property after 12 May 2026 and add a granny flat. The granny flat does not convert it into a new build. From 1 July 2027, the whole title stays quarantined. The strategy still works on its merits, and the yield uplift is unaffected, but it will not rescue the tax treatment, and you should not buy assuming it will.
Scenario three: separately titled dual occupancy or subdivision. Genuinely unresolved. There is a reasonable argument that a newly constructed, separately titled dwelling is a new dwelling in its own right. Against that, the government’s stated position runs the other way, and in New South Wales you cannot subdivide a lot containing a secondary dwelling anyway, which closes off the cleanest path in the biggest market. If you are relying on this, get written advice.
Two related points. Quarantined deductions are deferred, not destroyed. In scenario two, depreciation on a new granny flat still generates deductions; they just cannot reduce your salary income. They accumulate against future rental income or the eventual capital gain, which makes proper depreciation records more important now, not less.
If the granny flat is on the home you live in, renting it out partially forfeits your main residence exemption, apportioned by floor area and time. There is a separate CGT exemption for genuine family granny flat arrangements, but it applies only to non-commercial arrangements for someone of pension age or with a qualifying disability. Charging market rent disqualifies you entirely. Do not confuse the two.
What changed: the planning rules
Every state has moved, and mostly in your favour. The headline numbers, as they stand in August 2026:
| State | Max size | Minimum lot | Rent to anyone? |
|---|---|---|---|
| NSW | 60m² | 450m² for complying development | Yes, subdivision prohibited |
| Qld | Set council by council, 60m² to 90m² or more | Council dependent | Yes, since Sept 2022, statewide |
| Vic | 60m² | None for the exemption; permit needed under 300m² | Yes, since Dec 2023, not subdividable |
| WA | 70m² | Removed in 2024, any lot size | Yes |
| SA | Around 70m² | Existing allotments | Yes, since Nov 2023 |
| Tas | 60m², amendment pending to lift to 90m² | Council dependent | Yes |
Four things the table cannot carry. In New South Wales, a July 2025 clarification means the maximum floor area calculation counts the principal dwelling, the secondary dwelling and any attached carport, garage, balcony, deck, patio, pergola, terrace or verandah, so check the combined figure rather than just the 60 square metres of the flat. Complying development there runs 10 to 20 business days against 40 to 90 for a development application, which is the single biggest lever on your timeline.
Victoria adjusted its standards for smaller lots again in September 2025, so if you looked at this two years ago, the answer may have moved, and a building permit is always required regardless of the planning exemption.
South Australia’s November 2023 change overrode existing approval conditions that restricted occupancy to family, so if you hold an older approval, it is worth re-reading.
And Tasmania’s move from 60 square metres to 90 is not law yet. Do not buy on the assumption that it will be.
Every state has been loosening secondary dwelling rules to get supply moving. Planning is no longer the binding constraint on this strategy. Cost is.
All of the above is a general summary as at August 2026. Planning rules change, councils interpret them differently, and the detail that decides your site is usually local. Confirm the current position with the relevant council or a town planner before relying on any of it.
The numbers, honestly
We need to be blunt here, because the figures circulating on this topic are close to fiction.
There are two entirely different price universes in granny flat costing. The advertised base build price, which is what gets you to call. And the all-in delivered cost, which is what you actually pay. They differ by roughly a factor of two, and almost every yield calculation you will read online quietly uses the first number.
What a build actually costs in 2026. In New South Wales, a two-bedroom detached build with reasonable finishes has been landing for us somewhere from the high $100,000s to around $300,000 all in, depending on site costs, design, approvals and inclusions. One bedroom sits lower, three bedrooms higher. Western Australia has run dearer, on trade shortages and materials. Queensland and South Australia have been cheaper, though less cheap than they were.
The variance sits in what nobody quotes. Service connections, particularly if your sewer runs on the wrong side of the property, can add tens of thousands on their own. Site preparation on a sloped or rocky block escalates fast. A geotechnical report costs around a thousand dollars and is the cheapest insurance you will ever buy. Cost inflation itself has calmed down, running around 2.8% over the year to June 2026. The problem is not the rate of increase; it is that the base never came back down after the pandemic.
What they rent for. This has held up genuinely well. Some of our own client projects, banded and de-identified. Three are completed builds and conversions from before mid-2025, so read them against costs of that time rather than today’s; a fourth is a conversion currently underway, priced at today’s costs. A two-bedroom detached build in New South Wales in the high $100,000s that leased in the mid-$500s a week. A two-bedroom in Western Australia just under $200,000 that leased at around $500. A conversion rather than a build, which is a different exercise again: an underutilised detached double garage in Queensland converted to a self-contained one-bedroom for under $60,000, leasing in the low $400s. And, still in progress, another conversion: an outbuilding being converted into a self-contained one-bedroom flat for an estimated $70,000, with expected rent of $350 to $380 a week once it is tenanted.
Those are specific projects, not typical results, and one of them has not been completed yet. Most sit at or above the top of the range we set out below, which is precisely why we give you the range rather than the highlights. Your result will depend entirely on your site, your market, your build and when you build it.
What the yield actually is. You will see 20% and higher quoted routinely, arrived at by dividing rent by a base build price nobody pays. On a genuine all-in basis the honest range is around 8% to 13% gross and 6% to 10% net after management and maintenance.
Still an excellent number, two to three times what the underlying house yields. It does not need inflating, and we would rather you plan on the real figure and be pleasantly surprised than plan on the fantasy and get caught short. The more useful metric is the combined yield: a house yielding 3% to 4% can move to between 5.5% and 7% once a granny flat is on it, and the combined number is what changes a portfolio.
The valuation reality. In our experience, valuers commonly recognise something in the order of half to two thirds of build cost as additional property value, though it varies by valuer, by market and by build quality. On a $250,000 build, purely as an illustration, that would be roughly $125,000 to $165,000, leaving a paper shortfall on day one that only closes over years of rental income. If your plan is to build, revalue, extract the full cost and repeat, the numbers frequently do not work.
One decision moves that valuation more than any other, and it is compliance. A properly approved granny flat with an occupation certificate and separately metered services values materially better than an unapproved or shared-service one. Valuers weight evidenced rental income, construction quality, separation of services and documentation. Compliance documentation typically costs a few thousand dollars, and on the projects we have run it has consistently been money well spent at valuation time. We will not put a number on it, because it varies by valuer and by market. It is still the cheapest thing on this list with the largest effect on the outcome.
The site checklist
Before anything else:
Land size and zoning. Meet the state minimum for compliant development and you fast-track. Miss it by a metre, and you are in a development application, which is months rather than weeks and considerably more expensive.
Access. How does the tenant get in, and how does the builder get a machine in? We had a client target a site an agent had confidently called a granny flat block. When our people walked it, the side access was borderline: air conditioning units and years of clutter down the side of the house, and no way to get a bobcat through. The alternative is craning the build in over the roof. Somebody pays for that crane, and it is not the agent. Michael was a sparky before he was an investor, which is why he looks down the side of a house before he looks at the price.
Setbacks and services. Setbacks change with land size. In New South Wales, a block between 450 and 900 square metres typically carries a three metre rear setback. Go to 901, and it becomes five. Then find your power, water and sewer and check they can carry another dwelling, because a sewer running through the back that needs encasing is a real cost.
Overlays and title. Flooding, bushfire, slope, easements, encumbrances, restrictions on title. Skip these, and you will find them later, expensively.
Demographic fit. Ignored most often, and it determines whether the strategy works at all. If the surrounding market is large blocks, standalone homes and predominantly owner-occupied, a granny flat squeezed onto the site works against you. Cram it in so most of the land is built out, and a valuer will treat it as a negative. Michael saw plenty of those on the tools years ago. Gutters almost touching, no backyard left at all. They got built. They did not value well.
It is also the answer on metro versus regional. It stacks up more often in metro, where you have better access to trades, fewer delays, and tenants already used to a dual-living setup. Regionally it depends on the demographic. Where every renter wants a big backyard and a shed, you are working against the grain. In a regional centre built around a university, a hospital or one big employer, it works well.
One extra for conversions. The mistake we see most is ceiling height. People measure 2.1 metres and assume they are fine. Bedrooms need 2.4 metres, and the flooring takes some of that back.
Process, and the mistakes
Assuming the site checks out: set a realistic budget including approvals, site prep and utilities, assemble the team, and submit for approval, ideally through complying development. Then specify the build, which is where money leaks. Investors go for the bare minimum, then realise at the back end that they wanted air conditioning, another power point, better appliances. Done upfront, it costs a fraction. Done as a late variation, builders will slug you for it, and they are entitled to. If you are running it yourself, have a property manager review the plans. They will come back with “not enough light, not enough power points” within five minutes, which is exactly what your tenants would have told you six months later.
Before you sign off, get an independent building inspection. Not the builder’s. We have had defects and non-compliance flagged at this stage on multiple projects and rectified before handover. Sign off without it, and you inherit those problems with tenants already in place.
Realistic timeline from decision to keys, assuming no hiccups: nine to eighteen months for a new build, with complying development rather than a development application the biggest single lever on that.
The mistakes we see most often. Believing the listing. Every second advertisement says second dwelling potential, STCA, subject to council approval. It commits nobody to anything; it costs the agent nothing to write, and we have argued with agents about it more than once. The due diligence is where this is won or lost, and no block is a granny flat block until somebody has actually checked. Executing it badly: shared bathrooms, unclear yard boundaries, no soundproofing, services that were never separated, all of which become permanent tenant headaches and permanent valuation discounts. And going all-in on one strategy because everybody is talking about it, when the better move is often to keep scaling the portfolio while you can and come back to the value-add play when you actually need the cash flow.
So does it still stack up?
Yes, with conditions.
Planning has moved in your favour in almost every state. The demand side has not softened. National vacancy was 1.3% in June 2026 and asking rents were up 8.1% over the year (SQM Research), and the tenant for a well-built two-bedroom flat behind a house is exactly the tenant with nowhere else to go. And on a well-executed project, the yield uplift remains one of the few ways to improve a portfolio’s position without waiting on the market, even at today’s build costs.
What has changed is that you can no longer treat it as a tax play. If you owned before Budget night, very little changed for you. If you bought after, build it because the cash flow and the serviceability improvement justify it, not because you think it fixes your deduction. It does not.
And none of this decides itself. Where you are in your journey changes the answer. Investors with a long runway often weight growth more heavily. Investors under cash flow pressure, or with equity they cannot otherwise deploy, often weight yield. Working out which of those you are, and what follows from it, is not something an article can do for you.
One more thing. If you are using a buyer’s agent who says they do this, ask who they work with and how many they have actually finished. You do not want someone learning on your portfolio.
If you would like us to look at whether your site stacks up, book a call. We are a buyer’s agency and property advisory firm, not a licensed financial adviser, tax agent, credit provider or town planner, so anything tax, lending or planning related will need the relevant specialist alongside us. Plenty of those calls end with us telling someone the block will not take one. It is a cheaper answer to get from us than from a builder.