South Australia made a quiet but significant change to granny flat rules that many Adelaide homeowners still have not caught up with. For decades, ancillary accommodation in this state came with an occupancy restriction: it could only be occupied by a person dependent on, or related to, the occupants of the main dwelling. Renting it to a stranger was an offence. That restriction has been removed. Existing ancillary accommodation can now be rented to anyone, even where the original development approval limited its use or restricted occupation to family.
That single change transformed granny flats in Adelaide from a family-housing solution into an investment proposition, and the market has responded. This guide covers the rules, the costs, the realistic returns and the traps.
What the Rules Now Say
The rental reform
The Planning, Development and Infrastructure (General) (Ancillary Accommodation and Schedule 6A) Amendment Regulations removed the occupancy restriction on ancillary accommodation. In practical terms:
- Existing granny flats can be rented to anyone, regardless of what the original approval said about occupancy
- It is no longer an offence to enter into a residential tenancy agreement for a granny flat with a person unrelated to the main dwelling’s occupants
- The reform was introduced to add supply to a tight rental market, and applies retrospectively to accommodation already approved and built
This is the point people miss: you do not need a new approval to rent out a granny flat approved years ago under the old occupancy conditions. The regulation change overrides those conditions.
What ancillary accommodation still is
Ancillary accommodation remains ancillary — it is subordinate to the main dwelling on the same allotment. That has consequences:
- It shares the allotment and cannot be separately titled without a subdivision, which is a different and much larger application
- It cannot be sold separately
- It typically shares the main dwelling’s services connections, though separate metering is possible and worth doing
- It is subject to size and siting limits set by the Planning and Design Code and the applicable zone
If you want a genuinely separate, separately saleable dwelling, you are looking at subdivision and a second dwelling rather than ancillary accommodation, and the planning pathway, the cost and the timeframe are all substantially larger.
Approval: What You Need
A granny flat needs both planning consent and building consent, combining into Development Approval. Lodgement is through the PlanSA portal.
For more detail on this part of the project, see Converting Part of Your House into a Granny Flat: Separation and Services.
The criteria that govern the pathway
The Code sets criteria for ancillary accommodation covering floor area, height, setbacks, site coverage, private open space and separation from the main dwelling. Meeting all applicable deemed-to-satisfy criteria means planning consent must be granted within 5 business days. Missing one moves you to performance assessment at 20 business days, or 70 if public notification is triggered.
The criteria that most often push an Adelaide granny flat out of the fast pathway:
- Floor area above the specified maximum for the zone
- Site coverage where the main dwelling already occupies a large share of the allotment
- Private open space — the main dwelling must retain its required area and minimum dimensions after the granny flat is built, which is what kills most proposals on smaller inner-suburban blocks
- Boundary setbacks and wall height on boundary
- Overshadowing and overlooking of the neighbouring property
- Vehicle parking requirements in the applicable zone
Check the property’s zone and overlays on the Planning and Design Code mapping tool before you commission a design. Heritage, character, bushfire and flooding overlays all add requirements, and in a Historic Area Overlay the granny flat’s visibility from the street becomes a live issue.
Building consent requirements
A granny flat is a Class 1a building and must meet the full National Construction Code — structural adequacy, energy efficiency including NatHERS compliance, waterproofing to AS 3740, glazing, smoke alarms, and accessibility of services. It is a house, not a shed, and it is priced accordingly.
What a Granny Flat Costs in Adelaide
Build cost by type and size
- Studio, 25 to 35 square metres: $110,000 to $165,000
- One bedroom, 40 to 50 square metres: $150,000 to $230,000
- Two bedroom, 55 to 70 square metres: $200,000 to $310,000
- High-specification or architect-designed: $4,500 to $6,500 per square metre and up
As a rate, a well-built Adelaide granny flat sits at roughly $3,600 to $4,800 per square metre. Kit and modular products advertise lower rates, but the advertised price is typically the building only, delivered — site works, footings, connections, approvals, driveway, landscaping and fencing are all additional and commonly add $50,000 to $100,000.
The costs that sit outside the build price
- Site classification and footing design: $600 to $1,200 for the test. On Adelaide’s H2 and E class clay sites, the footing system itself can be $15,000 to $40,000 for a granny flat — a far larger share of the total than it would be in a low-reactivity city.
- Service connections: $8,000 to $30,000. Water, sewer, power and often a switchboard upgrade to the main dwelling. Trenching the length of a long block through established garden is not cheap, and if the sewer connection point is at the front of the property while the granny flat is at the rear, you may need a pump-out system.
- Separate metering: $3,000 to $8,000 for power and water. Worth doing if you are renting — it removes the single largest source of tenancy friction.
- Approval and professional fees: $6,000 to $18,000 across design, engineering, energy rating, lodgement, planning consent, building consent and the CITF levy.
- Site works: excavation, retaining, drainage and a paved path or driveway. $10,000 to $40,000 depending on the fall across the site.
- Demolition or tree removal to clear the footprint, including any regulated tree assessment.
A realistic all-in figure for a two-bedroom granny flat on a typical Adelaide block, done properly, is $260,000 to $380,000. Anyone quoting $140,000 all-in for a two-bedroom is quoting the building and leaving you to discover the rest.
The Return
Rental income
Adelaide granny flat rents vary widely by location and quality. Broad current ranges:
- Studio: $260 to $360 per week
- One bedroom: $330 to $450 per week
- Two bedroom: $400 to $560 per week
- Inner suburbs and coastal locations sit at the top of these ranges; outer northern and southern suburbs at the bottom
Doing the yield calculation honestly
Take a two-bedroom granny flat at an all-in cost of $310,000 renting for $470 per week:
- Gross annual rent: approximately $24,440
- Gross yield on cost: approximately 7.9 per cent
- Less rates, insurance, maintenance, property management, vacancy allowance and increased land tax exposure — call it 25 to 30 per cent
- Net yield: roughly 5.5 to 6 per cent on cost
That is a solid return by Australian residential standards, and materially better than the yield on the main dwelling. It works because you are not buying land — you already own it.
The effect on property value
A well-designed, properly approved granny flat generally adds less to the property’s value than it cost to build — typically 60 to 85 per cent of the build cost. The return comes from the income, not the capital gain. It also narrows your buyer pool slightly at resale, because some buyers want a large yard rather than a second building on it.
The tax and rates points to check
- Land tax. Renting out part of your property can affect the principal place of residence exemption. Get advice specific to your circumstances before you build.
- Capital gains tax. Using part of your home to produce income can partially remove the main residence CGT exemption for the period and proportion of income-producing use.
- Council rates. Some councils reassess the property once a second dwelling is occupied.
- Depreciation. A new granny flat generates substantial depreciation deductions on both the building and the plant and equipment — commission a depreciation schedule.
None of this is a reason not to build one. All of it is a reason to talk to an accountant before you do rather than after.
Designing a Granny Flat That Rents Well
- Give it a genuinely separate entry and its own address presentation. Tenants pay a premium for not walking past the main house’s windows to reach their front door.
- Separate the outdoor space with real fencing and screening, not a token line of shrubs. Privacy in both directions is what makes the arrangement sustainable.
- Meter it separately. Shared utilities are the number one source of disputes in ancillary accommodation tenancies.
- Provide a proper laundry, even a European-style one in a cupboard. Sharing the main house’s laundry does not work with an unrelated tenant.
- Include a car space if the zone permits it and the site allows. In most Adelaide suburbs this materially affects rentability.
- Insulate and orient properly. A small, poorly oriented building with a large west-facing window is brutal in an Adelaide summer. Living area to the north, minimal west glazing, generous eaves, and ceiling insulation well above the minimum.
- Specify a reverse-cycle split system sized correctly. This is not optional in this climate.
- Give it real storage. Small dwellings live or die on storage, and a built-in robe plus a linen cupboard costs very little at construction.
- Use the same material palette as the main house where the granny flat is visible, both for approval reasons and for resale.
The Common Mistakes
- Not checking private open space first. The most frequent reason an Adelaide granny flat proposal fails is that the main dwelling would be left below its required open space after the second building goes in. Check this before anything else.
- Believing the kit price. The advertised figure is the building. Site works, footings, connections, approvals and landscaping are typically 40 to 70 per cent more.
- Underestimating the footings. On Adelaide’s reactive clay, a granny flat needs the same engineered footing system as a house. Kit suppliers quoting a simple slab on an E-class site are not quoting a compliant building.
- Not separating services. Retrofitting separate metering after construction costs several times what it costs during.
- Building without approval. An unapproved second dwelling is uninsurable, unrentable through an agent, and a serious problem at sale. It also cannot be regularised easily if it does not meet the Code.
- Assuming a shed conversion is cheaper. Converting an existing outbuilding to habitable use requires it to meet the full Class 1a standard — footings, energy performance, waterproofing, glazing, ventilation. In most cases the compliance upgrade costs more than building new.
- Ignoring the overlays. A bushfire overlay in the Hills adds BAL construction requirements; a heritage overlay affects siting and materials; a flooding overlay drives floor levels.
Is It Worth It?
For an Adelaide homeowner with a block that can accommodate one without compromising the main dwelling’s open space, a granny flat is one of the better returns available on residential capital. You get a 5.5 to 6 per cent net yield on cost, meaningful depreciation deductions, and a flexible asset that can house family, produce income, or become a home office or studio as circumstances change.
It stops being worth it when the block is too tight, when the site classification pushes the footing cost into the stratosphere, or when the service connections require a long run and a pump station. Those things are all knowable before you spend anything beyond a soil test and an hour of a designer’s time — which is exactly the order in which they should be investigated.
For related decisions, see home extensions in Adelaide if the alternative is adding to the main house, and the 2026 approval rules for the wider planning framework.
Choosing Between Kit, Modular and Site-Built
There are three ways to build ancillary accommodation in Adelaide, and the right choice depends more on the site than on the price list.
A related guide to consider while planning this work is Do You Need Council Approval to Renovate in Adelaide? The 2026 Rules Explained.
Kit and flat-pack
- Advertised price: the lowest, and the least complete. The figure typically covers the building components delivered, and excludes footings, site works, connections, approvals, internal fit-out and finishing.
- Best for: flat, accessible sites where the owner is comfortable coordinating trades, and where the design does not need to respond to the main dwelling.
- Watch for: whether the design has been engineered for an H2 or E class site. Many kit systems are supplied with a generic slab detail that is not compliant on Adelaide’s reactive clay.
Modular and transportable
- Cost: mid-range, with a shorter on-site program because the building arrives largely complete
- Best for: sites with good crane and truck access, and owners who want a fixed price and a short disruption
- Watch for: access. Getting a module into a rear yard on a typical inner-suburban Adelaide block, past a retained villa with a 900 millimetre side setback, is frequently impossible. Check this before anything else.
Site-built
- Cost: highest per square metre, and the most predictable once designed
- Best for: constrained sites, sloping sites, heritage and character areas where the building must respond to the main dwelling, and any site where the design needs to work around trees, levels or existing structures
- Advantage: the design can be optimised for orientation, privacy and the specific block, which materially affects rentability
How to compare them honestly
Ask every supplier for a written all-in price that includes: footings designed to your actual site classification, all site works and excavation, water, sewer, power and data connections, separate metering, all approval and professional fees, the CITF levy, driveway or path access, fencing and screening, and landscaping to the extent required by the approval. Very few advertised prices include more than half of that list, and the ones that do are the comparison you want.
Being a Landlord in Your Own Backyard
The reform allowing ancillary accommodation to be rented to anyone changed the economics. It also changed the day-to-day reality, and the practical side deserves as much thought as the build.
- Use a property manager. The 6 to 9 per cent fee is worth it when the tenant lives twenty metres away and every conversation would otherwise be a doorstep negotiation.
- Separate the services properly. Individually metered power and water removes the single largest source of dispute in shared-title tenancies.
- Define the boundaries physically. Real fencing, a separate gate, a separate path, separate bins and a clearly allocated car space. Ambiguity about shared space is what makes these arrangements fail.
- Put the outdoor areas back to back, not face to face. The granny flat’s private open space should not look into the main dwelling’s, and vice versa.
- Screen sightlines from windows, in both directions, at the design stage rather than with a hastily planted hedge later.
- Set expectations in the tenancy agreement about access, parking, noise and the use of common areas.
- Consider the insurance. Landlord insurance for the tenanted portion, and confirm your home and contents policy covers the arrangement.
- Get tax advice before the first tenant moves in, particularly on land tax, the main residence CGT exemption and the depreciation schedule.