The 7-Star NABERS Mandate: What Owner-Builders Actually Have to Do
The short version. If you are building a granny flat, a secondary dwelling, or a new house as an owner-builder, the scheme you have to satisfy is NatHERS (Nationwide House Energy Rating Scheme), not NABERS. NABERS rates the measured performance of commercial buildings and apartment base buildings, and it almost certainly has nothing to do with your block. Under NCC 2022, a new Class 1 dwelling needs a minimum 7-star NatHERS thermal rating plus a Whole-of-Home score of 60 or better, and NSW runs the same intent through BASIX instead. Western Australia only made those provisions mandatory on 1 May 2025, which means most WA designs drawn before that date are 6-star designs and will not pass. On a 60m² secondary dwelling, the honest uplift from a 6-star design to a compliant 7-star design lands between $4,000 and $12,000 depending on climate zone and how much glass you have drawn. The assessment itself is the cheap part, sitting between $350 and $650. Get the rating modelled before you finalise the plans, not after, because every change after lodgement costs you a re-run and a resubmission.
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A caller rang us last winter about a two-bedroom flat behind his house in the Illawarra. His supplier had told him the design was “7-star NABERS certified,” and he wanted us to draw the working drawings around it. We asked to see the certificate. What came through was a NatHERS certificate for the same floor plan, modelled on a different lot, facing north, in climate zone 5. His block faced the other way and sat on a slope with a two-storey neighbour shading the living room glass for most of the day. The plan was fine. The rating was not his.
That is the practical heart of this article. A star rating is not a property of a floor plan. It is a property of a specific dwelling, on a specific lot, with a specific orientation, glazing schedule, shading, and construction system, assessed in approved software by an accredited assessor. Under NCC 2022, a new Class 1 dwelling has to reach a minimum of 7 stars for thermal performance, plus a separate Whole-of-Home energy budget covering hot water, heating, cooling, lighting, and any solar you install. Both apply to owner-builders exactly the same way they apply to a volume builder. Nobody gets a smaller obligation for doing the project themselves.
NABERS, NatHERS, and BASIX: three schemes, and only one of them is yours
We hear NABERS thrown around on residential jobs more often than we should, and it is usually a supplier borrowing a word that sounds official. Here is the split, in plain terms.
NABERS (National Australian Built Environment Rating System) rates measured, real-world performance after a building is operating. It covers offices, shopping centres, hotels, data centres, and the base building energy and water use of apartment buildings. It works off twelve months of actual bills and meter data. You cannot get a NABERS rating on a granny flat, because there is no NABERS tool that applies to a detached Class 1a dwelling, and there is no meter history on a building you have not built.
NatHERS (Nationwide House Energy Rating Scheme) is the one that binds you. It rates the predicted thermal performance of the building shell on a scale of 0 to 10 stars, using software approved under the scheme (AccuRate Sustainability, BERS Pro, FirstRate5, and HERO are the main ones). Since NCC 2022, NatHERS also produces a Whole-of-Home score covering fixed appliances and onsite solar. A new house or secondary dwelling needs 7 stars for the shell and a Whole-of-Home score of at least 60. Class 2 apartments run on a different arrangement, with an average across units and a floor for individual units.
BASIX (Building Sustainability Index) is New South Wales doing its own thing. NSW never adopted the NatHERS star figure directly into its planning system. Instead, BASIX sets thermal comfort caps and energy and water targets, and the thermal comfort side was lifted on 1 October 2023 to sit at roughly the same level as 7 stars. Same destination, different certificate, different lodgement path.
So if a quote, a brochure, or a sales rep says NABERS on a granny flat, that is not a sign of rigour. It is a sign nobody in the chain has read the code.
What 7 stars actually costs on a 60m² build
The assessment fee is not where the money goes, and that is the part owner-builders get wrong most often. We have watched people shop three assessors to save $150, then spend $6,000 on double glazing they could have avoided by moving two windows 900mm and pulling the western glass back under a wider eave. The modelling is cheap. What the modelling tells you to build is not.
Below are the numbers we see on 45m² to 60m² secondary dwellings in 2026, across NSW, WA, VIC, QLD, and TAS. These are supplied-and-installed figures for a small dwelling, not per-square-metre rates for a full house.
| Item | Typical cost | What drives it |
|---|---|---|
| NatHERS assessment, first pass (thermal + Whole-of-Home) | $350 to $650 | Number of zones, complexity, turnaround |
| Re-run after design changes | $120 to $250 per revision | How many windows you moved |
| NSW BASIX certificate (government fee, single dwelling) | $60 to $150 | Set by NSW Planning, changes periodically |
| Ceiling insulation, R5.0 to R6.0 | $250 to $800 | Roof form, access, batt vs blanket |
| Wall batts R2.0 to R2.7 plus vapour-permeable wrap | $700 to $1,600 | Wall area, cladding system |
| Suspended timber floor insulation, R2.5 | $1,500 to $3,500 | 60m² footprint, subfloor clearance |
| Slab edge insulation (climate zones 6 and 7) | $700 to $2,000 | Perimeter length, waffle vs raft slab |
| Glazing upgrade, single-glazed aluminium to double-glazed uPVC or thermally broken | $3,000 to $8,000 | 12m² to 16m² of glass is the usual range |
| Draught sealing, sealed downlights, damped exhaust fans | $500 to $1,500 | Number of penetrations |
| Heat pump hot water, installed after STCs | $1,800 to $3,800 | Unit choice, state rebate, plumbing runs |
| High-efficiency reverse-cycle split system | $2,200 to $3,800 | Capacity, single head vs multi |
| Rooftop solar, 3kW to 6.6kW after STCs | $3,200 to $7,000 | Roof pitch, orientation, switchboard upgrade |
| Ceiling fans, two to three units | $400 to $1,000 | Helps thermal comfort and Whole-of-Home cheaply |
| Total realistic uplift, 6-star design to compliant 7-star | $4,000 to $12,000 | Climate zone, glazing area, orientation |
Two honest observations about that table. First, in climate zone 2 (Brisbane, the Gold Coast, most of the Queensland coast) the uplift sits at the bottom of that range, because the shell is not fighting a cold winter and you can often reach 7 stars with good eaves, ceiling insulation, ceiling fans, and single-glazed glass with a decent frame. Second, in climate zone 7 (most of Tasmania, the Victorian high country, the NSW tablelands) the uplift sits at the top, and double glazing stops being a choice.
The other cost nobody quotes you is the cost of finding out late. A revision to the NatHERS model is $200. A revision to the NatHERS model after your building certifier has issued the permit, your slab is poured, and your window order is in production is a variation, a resubmission, and a delay. We have seen a window schedule change on a granny flat add nine weeks because the uPVC units were a six-week lead time and the original aluminium order had already been cut. If you want a realistic picture of how that flows through a program, our stage-by-stage granny flat build timeline sets out where the slack actually is.
What Draftee does. We are an architectural drafting firm. We produce the planning and construction drawings, the window and door schedules, the sections and details your certifier and your energy assessor need, and we coordinate the documentation so the compliance package lines up before anything is lodged. We draw the plans, we don’t sell buildings. That distinction matters on this topic in particular, because a supplier who is selling you a kit has a commercial reason to keep the glazing spec cheap and the star rating vague until after you have paid a deposit. We have no product to protect. If the model says your north-facing glass needs to grow and your west-facing glass needs to shrink, we will draw it that way and tell you what it does to your build cost.
New South Wales: BASIX does the talking
The most common NSW mistake we see is an owner-builder chasing a NatHERS certificate for a secondary dwelling and then discovering their certifier wants a BASIX certificate instead. Both can be true at once, and the sequence is not obvious from the outside.
The pathway, and where the certificate fits
Most granny flats in NSW go through complying development under State Environmental Planning Policy (Housing) 2021. The headline numbers are a minimum lot size of 450m², a maximum floor area of 60m² for the secondary dwelling, and one secondary dwelling per lot. If you meet every criterion, a registered certifier can issue a Complying Development Certificate (CDC) rather than the council issuing a development consent, and that pathway typically runs 20 to 40 business days from a complete lodgement. If you miss a single control, you are into a development application with council and a realistic 3 to 6 month window instead.
A BASIX certificate has to be attached to that lodgement. You generate it through the NSW Planning Portal, and the commitments listed on it become conditions of your approval. That means the insulation R-values, the glazing performance, the hot water system, the fixture flow rates, and the lighting all become legally enforceable items your certifier will inspect against. Change the hot water system on site because a mate can get you a cheaper unit, and you have technically breached a condition of your approval.
What the thermal comfort target means in practice
BASIX has three parts: water, thermal comfort, and energy. Since the Sustainable Buildings SEPP commenced on 1 October 2023, the thermal comfort and energy targets have been lifted to sit in line with the intent of NCC 2022. For thermal comfort you can either use the simulation method, which requires an accredited assessor to run the dwelling in NatHERS software and enter the heating and cooling loads, or the DIY method, which uses prescriptive tables. On a small secondary dwelling with a decent orientation, the DIY method sometimes works. On a tight block, a south-facing living area, or a design with more than about 20% of the floor area in glass, the simulation route almost always gives you a cheaper build, because it lets you trade a good roof and good shading against expensive windows.
That trade is the whole game. A prescriptive table cannot see that your western wall is shaded by a neighbour’s garage. Software can.
Owner-builder specifics in NSW
You need an owner-builder permit from NSW Fair Trading for residential building work valued above $10,000, and you need to complete the approved owner-builder course before you apply. Home Building Compensation cover does not apply to owner-builders, which changes your position if you sell within six years. We have covered the consequences in detail in our guide to owner-builder insurance and warranty in Australia, and it is worth reading before you commit, not after.
For cost context on the rest of the build, our granny flat cost Sydney breakdown gives real 2026 figures by bedroom count, and the 2 bedroom granny flat prices state-by-state comparison shows how far Sydney sits above the national middle.
Permit check. Not certain whether your secondary dwelling qualifies as complying development or whether you are heading into a development application? Run your address and your intended works through doineedapermit.au before you spend money on drawings. It takes two minutes and it changes your whole program if the answer surprises you.
Victoria: the permit date decides which rules you get
Victoria delayed the NCC 2022 energy provisions, and that delay still causes arguments on site in 2026. The date that matters is the date you applied for your building permit, not the date you started drawing and not the date you poured.
1 May 2024 and the transition
Victoria brought the NCC 2022 residential energy efficiency provisions into effect for building permit applications lodged on or after 1 May 2024. Applications lodged before that sat under the old 6-star regime. Practically speaking, every new application now falls under 7 stars plus Whole-of-Home, and any old design you have been handed by a supplier or a friend who built in 2022 is a 6-star design. It will not pass. We have re-documented three flats in the last eighteen months that were drawn to a 6-star spec and shelved for a year while the owner saved money, and in each case the glazing and insulation schedule had to be rebuilt from scratch. Nobody enjoys paying twice for the same drawings.
All-electric, and what it does to your Whole-of-Home score
Since 1 January 2024, new homes and residential subdivisions in Victoria that require a planning permit must be all-electric. No new gas connection. For an owner-builder this reads like a constraint and behaves like a gift, because the Whole-of-Home calculation rewards a heat pump hot water unit and a high-efficiency reverse-cycle split far more generously than it rewards gas. A 3kW to 5kW solar array on the flat’s roof pushes the score higher again. On the jobs we document, a small all-electric dwelling with heat pump hot water, one efficient split system, LED lighting, and a modest array clears the Whole-of-Home requirement comfortably, which means the thermal side of the model can carry the tighter part of the compliance load and you have room to negotiate on glass.
Climate zone is not a state-wide answer
Melbourne sits in climate zone 6. The state’s north runs into climate zone 4, with hot dry summers and cold winters, and the high country runs to zone 7. Those are different buildings. In zone 6 we typically land 7 stars on a 60m² flat with R6.0 ceiling insulation, R2.7 walls with a vapour-permeable wrap, slab edge insulation, double-glazed windows on the south and west, and eaves that actually shade something in January. In zone 4 the summer load flips the priorities and external shading on the west elevation earns more stars per dollar than an extra glazing upgrade. In zone 7 you are budgeting for double glazing everywhere and thinking hard about thermal bridging.
For Victorian cost benchmarks on the rest of the build, our granny flat cost Melbourne figures set out what the trades are actually charging in 2026.
Where we sit in the process. We draw the documentation set your assessor models from and your surveyor assesses. That means our window schedule, our sections, and our construction notes have to agree with the NatHERS certificate line for line. When they do not, the building surveyor sends the lot back, and the owner-builder loses a fortnight for a mismatch that should have taken ten minutes to coordinate.
Queensland: warmer climate, cheaper stars, tighter paperwork
Queensland is the state where owner-builders most often assume energy compliance will be brutal and find out it is manageable. The climate does a lot of the work for you. The paperwork does not.
Adoption and the certifier relationship
Queensland brought the NCC 2022 residential energy efficiency provisions into effect from 1 May 2024, and we would still confirm your transitional position against your building application date before you rely on it. Queensland also layers the Queensland Development Code over the NCC, and MP 4.1 (sustainable buildings) is the part that catches people out on water and energy items that the NatHERS certificate does not address.
Your building certifier is central in Queensland in a way that surprises interstate readers. They issue the development permit for building work, they call the inspections, and they collect the Form 15 and Form 16 certificates for design and installation of specified systems. If your energy assessment relies on a particular glazing product or insulation system, expect to be asked for evidence at inspection. Verbal assurance from a supplier is not evidence.
Climate zone 2 and what it changes
Brisbane, Logan, Ipswich, the Gold Coast, and the Sunshine Coast sit in climate zone 2. Townsville and Cairns are zone 1. In these zones the cooling load dominates, which means the cheap wins are shading, cross-ventilation, ceiling fans, a light-coloured roof, and a well-insulated ceiling. Wall insulation still helps. Double glazing usually does not pay for itself in stars, and we regularly get 7 stars in zone 2 on a 60m² flat with single-glazed aluminium windows carrying a decent frame and generous eaves.
Where zone 2 bites is elevated timber-floor construction. An unenclosed suspended floor over a well-ventilated subfloor is great for summer and costs you in the model unless you insulate it, and that is a $1,500 to $3,500 line on 60m². Decide it before you settle the floor system, not after your bearers are in.
Owner-builder permits and the six-year rule
In Queensland you need an owner-builder permit from the QBCC for building work valued above $11,000 on your own home, you must complete the approved course, and you cannot obtain another permit for six years. You are also required to disclose owner-builder status if you sell within six years. The full picture across every jurisdiction is in our walkthrough of owner-builder permits by state.
For build costs, our granny flat cost Brisbane breakdown covers real 2026 prices by bedroom count, including the site and services items that quotes routinely leave out.
Western Australia: the last state to 7 stars, and the detached house test
Western Australia took the longest run-up of any jurisdiction, and the consequence is that WA has more 6-star drawings still in circulation than anywhere else on the mainland. If a design was drawn for a Perth block before mid-2025, start from the assumption that it does not comply.
1 May 2025, and why a 2024 design will not pass
Volume Two of NCC 2022, which is the volume covering houses and ancillary dwellings, became mandatory in Western Australia on 1 May 2025. Until that date, building permit applications could still be made under NCC 2019 Amendment 1. That is a full year behind Victoria and Queensland, and roughly two years behind the original national timetable. The practical effect is that the standard design a supplier has been selling since 2023, or the plan a neighbour built to in 2024, is very likely modelled at 6 stars with no Whole-of-Home calculation attached at all.
WA also varies the national code more than most states, which catches out assessors and suppliers working across borders. The liveable housing provisions were not adopted here. The separate heating and cooling load limits have been handled differently from the eastern states, and a 2026 amendment to the Building Regulations made several provisions voluntary rather than mandatory. NCC 2025 became available in WA from 1 May 2026, with the option of continuing under NCC 2022 Amendment 2 until 30 April 2027. The residential energy benchmark is identical either way, because building ministers held it steady, but you have to nominate one edition and apply it consistently across the project. You cannot take the thermal provisions from one and the condensation provisions from the other.
None of that moves the headline. Seven stars, plus Whole-of-Home. Confirm the detail against Building and Energy’s current industry bulletins and your building surveyor, because WA’s variation list is longer than most and it has changed twice in two years.
The 70m² ancillary dwelling, and what the extra area does to the model
WA calls a granny flat an ancillary dwelling, and the planning position improved sharply on 10 April 2024. The revised R-Codes removed the minimum lot size, which had been 350m², and extended ancillary dwellings to grouped and strata lots rather than only lots with a single house on them. If your design is deemed-to-comply, meaning it stays within 70m² of internal floor area and meets the setbacks in your local planning scheme, you do not need planning approval at all. You go straight to a building permit from your local government. You can also rent it to whoever you like, with no family occupancy restriction.
That is a materially better planning position than NSW or Victoria, and owner-builders in Perth should understand what it buys them. It also changes the compliance arithmetic. Seventy square metres is ten more than the NSW cap, and every one of those ten is conditioned floor area the model has to heat and cool. In practice the larger footprint and the friendly climate zone pull against each other, and a Perth ancillary dwelling built to the full 70m² usually lands in the middle of the uplift range in the table above rather than at either end.
One detail worth holding onto. The 70m² figure is internal floor area. Verandahs, patios, and carports are treated separately, which makes WA one of the few places where the shading you want for the energy model is not counted against you in the planning assessment. Site cover limits still apply, so check them before you draw a wide verandah across the western elevation.
Climate zone 5, double brick, and where the stars actually come from
Perth sits in climate zone 5, which the code calls warm temperate. Bunbury and Esperance are also zone 5. Albany, Denmark, and Pemberton run to zone 6. Northam and Kalgoorlie sit in zone 4, with hot dry summers and genuinely cold winters that surprise people who think of WA as a warm state. Carnarvon is zone 3, and Broome, Karratha, and Port Hedland are zone 1.
In zone 5 a 60m² to 70m² ancillary dwelling generally reaches 7 stars with R5.0 to R6.0 ceiling insulation, R2.0 to R2.5 in the walls, eaves that do real work on the north and west, and glazing chosen for performance rather than simply reduced in quantity. Double glazing is often optional in Perth if the orientation is decent, which is not something anyone can say about Melbourne or Hobart. Thermally improved frames and a considered glass selection will frequently get you there for a fraction of the cost.
The WA-specific complication is double brick. Perth builds in double brick where the eastern states build in brick veneer or lightweight frame, and it changes the wall conversation entirely. Thermal mass only earns its keep in the model when it sits inboard of the insulation, and in a conventional double brick wall with cavity insulation a good part of that mass is on the wrong side of the line. Reverse brick veneer performs better in the software and almost nobody builds it. The point is not that you should fight your trades over wall construction on a 70m² flat. The point is that if your assessor has modelled a stud wall and your builder is quoting double brick, the certificate and the building do not describe the same thing, and your building surveyor will notice.
Owner-builder approval, and the detached house test
This is the part that catches WA owner-builders, and it is worth reading twice.
You need owner-builder approval where the value of the work exceeds $20,000, or $50,000 for a Class 10a shed or carport, and you cannot split one job into two smaller permits to duck under the threshold. Approval comes from the Building Services Board, administered by Building and Energy within the Department of Local Government, Industry Regulation and Safety. It has to be granted before you apply to your local government for a building permit, not alongside it. Applications go in on Form 75, you need a white card or WA blue card, and at least one applicant must have completed owner-builder training with WA-specific content within the previous 24 months. Processing has been running at around six weeks. Build that into your program rather than discovering it.
Now the test itself. Owner-builder work covers a detached Class 1a(i) dwelling, and Building and Energy is explicit that this includes a granny flat separate from the main house. It is equally explicit that additions or alterations creating a separate tenancy, including an ancillary dwelling, which share any common building element with another dwelling are not a detached house. The R-Codes will happily let you attach or integrate an ancillary dwelling. The owner-builder pathway will not. So the design decision to tuck the flat onto the back of the house, which looks on paper like a saving on walls and service runs, can quietly remove your ability to build it yourself. Decide it at concept stage, alongside orientation and floor system.
A few more WA settings that change decisions. You must intend to reside on the land when the work is finished, which rules out building for immediate sale, and where there are multiple dwellings on one lot you satisfy that requirement by living in one of them. The six-year gap between owner-builder approvals runs from the date the building permit is granted rather than the date of approval, and it can be waived for hardship or where the new permit covers the same land. Selling an owner-built dwelling within seven years of the permit being granted is an offence carrying a $10,000 penalty unless you have home indemnity insurance in place covering the balance of that period. Seven years, not six, and an offence rather than a disclosure obligation. The comparison across every jurisdiction is in our walkthrough of owner-builder permits by state.
Tasmania: climate zone 7 and the cost of being cold
Tasmania is the hardest state in which to hit 7 stars, and the only one where we will tell an owner-builder up front that the compliance uplift is likely to be five figures on anything larger than a studio.
The climate does not negotiate
Almost all of Tasmania sits in climate zone 7, with a small area of zone 8 in the highlands. Zone 7 is a heating-dominated climate, which means the model is judged largely on how well the building holds warmth through a Hobart winter. Single glazing is finished. Practically every 7-star dwelling we document in Tasmania has double-glazed uPVC or thermally broken aluminium windows, R6.0 or better in the ceiling, R2.7 walls with continuous insulation or a thermal break where the framing bridges, insulated slab edges or an insulated suspended floor, and a genuine focus on air tightness. That package sits between $8,000 and $14,000 above a mainland warm-climate spec on a 60m² dwelling.
The upside is real and we say it plainly, because it is the one part of this whole topic where the regulation and the owner’s interest point in the same direction. A well-sealed, well-insulated 60m² flat in Hobart costs a fraction of a leaky one to heat. Tenants notice. Elderly parents notice more.
Categories of work, and who signs what
Tasmania’s Building Act 2016 sorts building work into low-risk work, notifiable work, and permit work, and a new dwelling is permit work. That means a building surveyor, a designer with the appropriate accreditation, and a formal permit process before you start. Your energy compliance documentation is part of the permit package, and Tasmania’s Director of Building Control issues determinations that can vary how NCC provisions apply locally. We understand a Tasmanian amendment affecting residential provisions is in progress for 2026, so confirm the current determinations with your building surveyor before you lodge rather than relying on an article, including this one.
Owner-building in Tasmania
Tasmania administers owner-builder approval through Consumer, Building and Occupational Services, and the requirements are stricter than the mainland in several respects, including restrictions on how often you can act as an owner-builder and what work you are permitted to carry out yourself. If you are weighing which parts of the job you can legitimately take on, our guide to what owner-builders can actually do themselves sets out the line between work you can do and work that must be signed off by a licensed trade.
Bushfire attack level is the other Tasmanian cost multiplier, and it interacts with your glazing decisions directly, because BAL-rated windows and double-glazed windows are two different specifications that you would rather buy once. Our breakdown of the cost of building in bushfire and flood zones covers how those two requirements stack.
The design decisions that carry the rating
Most of the star rating is decided in about four hours of drawing, long before anyone opens the software. That is not an exaggeration. Once orientation, glazing area, glazing distribution, eave depth, and floor system are fixed, the model has very little room left to move, and every remaining lever is a product you have to buy.
Orientation comes first. On a 60m² dwelling with the living area facing north and a 600mm to 900mm eave, we can usually put 30% to 40% of the total glazing on that elevation and gain stars. Put the same living area on the west with no shading and you are paying for double glazing plus external blinds to claw back what the orientation gave away. On a rear-yard granny flat you often cannot rotate the building, but you can almost always move the living area to the good side of it and put the bathroom, laundry, and robes on the bad side. Wet areas and storage make excellent thermal buffers.
Glazing area is the second lever, and the one where owner-builders resist hardest. A 60m² flat with 16m² of glass is a very different compliance problem from the same flat with 10m². Sliding doors are the worst offender, both because of the area and because sliding tracks leak air. Two 1800mm sliders in a two-bedroom flat will cost you real money in fabric upgrades. One slider and one awning window at the other end will give you better cross-ventilation for less. We have made this mistake on our own documentation early on, over-glazing a south elevation for a view that turned out to be a neighbour’s colorbond fence, and the client paid for that view twice.
Floor system is third. Slab on ground with insulated edges performs well in cold climates and holds heat. A suspended timber floor is cheaper to build on a sloping site and needs insulation to stay in the game. Decide which one before you engage a structural engineer, because reversing that decision after footings are designed is a genuinely expensive change.
Then the fixed services. Heat pump hot water, a high-efficiency reverse-cycle split, LED lighting throughout, and a small solar array will lift a Whole-of-Home score from marginal to comfortable for $7,000 to $12,000 all up, and a good chunk of that comes back in state rebates and small-scale technology certificates. That is usually cheaper than chasing the same compliance outcome through the building shell alone.
Documentation is the deliverable. The reason we push these decisions early is that a compliance package only works if every document agrees. Floor plan, elevations, sections, window schedule, insulation notes, energy certificate, and the certifier’s checklist all have to say the same thing. When one of them disagrees, the whole submission stalls, and the owner-builder is the one waiting.
The order you do things in
The single most expensive owner-builder mistake in this space is not a bad decision. It is a good decision made in the wrong order. Here is the sequence that works.
1. Title and constraints check. Pull your title, easements, covenants, and any restrictions on use. Confirm your lot size against the minimum for the pathway you want. Check your climate zone, your bushfire attack level, and your flood overlay.
2. Planning pathway. Establish whether you are complying development, an exempt or notifiable pathway, or a full development or planning application. This decides your timeline more than anything else.
3. Concept design with the energy target in the room. Orientation, glazing distribution, eaves, and floor system decided against the target, not adjusted to it afterwards.
4. Preliminary energy assessment. A first-pass NatHERS run, or a BASIX draft in NSW, on the concept. Cheap, fast, and it tells you which upgrades you actually need.
5. Construction documentation. Working drawings, schedules, and details that match the assessment line for line. Structural engineering runs alongside.
6. Final certificate and lodgement. The stamped energy certificate goes in with the application. Its commitments become conditions.
7. Quote the documented job. Only now do you send it out for pricing. Quoting an undocumented job is how you end up comparing three numbers that describe three different buildings.
8. Owner-builder permit, insurance, and build. Permit in hand, cover in place, then site works.
Steps 3 and 4 are the ones people skip, and skipping them is what turns a $250 model re-run into a $9,000 variation.
Check the pathway before you draw. doineedapermit.au will tell you which approval track your project sits on in a couple of minutes. Knowing that before step 3 saves more money than any other single action in this list.
The next steps
If you have a block, a rough idea of what you want, and a compliance requirement you would rather not discover halfway through, the useful first step is a conversation about the site. Orientation, slope, setbacks, existing shading, climate zone, and your intended use will tell us more in five minutes than a floor plan will in an hour.
Tell us about your block and we will come back to you on what the documentation set needs to cover, what the likely compliance path is in your state, and what we would recommend deciding before anyone models anything.
Frequently Asked Questions
No. NABERS rates measured operational performance of commercial buildings and the base building services of apartment buildings, using twelve months of actual energy and water data. There is no NABERS tool for a detached Class 1a dwelling, and there is no data to rate before you build. If a supplier, agent, or consultant tells you your granny flat needs a NABERS rating, they have confused it with NatHERS, and we would take that as a signal to check the rest of their compliance advice as well. What you need is a NatHERS certificate from an accredited assessor, or a BASIX certificate if you are in New South Wales. Different scheme, different name, one letter apart.
Almost never. A NatHERS certificate is issued for a specific dwelling with a specific orientation, on a specific lot, in a specific climate zone, with a specific glazing and construction schedule. Rotate the same floor plan 90 degrees and the rating changes. Move it from Brisbane to Ballarat and it collapses. Add a two-storey neighbour shading the north glass and it drops again. Some suppliers advertise designs as “7-star ready,” which is not a compliance status. It means the design reached 7 stars once, somewhere, under conditions that may or may not resemble your site. Ask which climate zone and orientation the certificate was modelled for. If the answer is vague, assume you are paying for a new assessment.
A first-pass NatHERS assessment on a 45m² to 60m² secondary dwelling runs $350 to $650 in 2026, and that normally includes the Whole-of-Home calculation. Revisions after design changes cost $120 to $250 each. The work has to be done by an assessor accredited through a NatHERS assessor accrediting organisation, using approved software. In New South Wales the BASIX certificate is generated through the NSW Planning Portal, with a government fee under $150 for a single dwelling, and you can either complete it yourself using the DIY thermal comfort method or engage an assessor to run the simulation method. On tight or poorly oriented sites, the simulation route usually costs less overall because it lets you trade cheap upgrades against expensive ones.
On a 60m² flat, the compliance uplift over a 6-star design is $4,000 to $12,000 depending on climate zone and glazing area. On a $180,000 to $260,000 build, that is between 2% and 6%. It is not the item that breaks budgets. Site works, service connections, and undocumented variations break budgets. What does hurt is discovering the uplift after you have locked in a fixed-price quote based on a 6-star specification, because then it arrives as a variation with a margin on top. Model it early, put the real spec in the drawings, and price the documented job. The number stops being a surprise.
Building ministers agreed in 2024 to hold the residential energy provisions steady for a period rather than raising them again in the next code cycle, so 7 stars plus Whole-of-Home is the benchmark you should design to now. We are not going to predict what lands after that, because we do not know, and anyone who tells you they do is guessing. What we would say is that state adoption dates and local determinations have moved several times since NCC 2022 was published, particularly in Victoria, Queensland, and Tasmania. Confirm the current position with your building surveyor or certifier against your application date. That is a five-minute phone call that protects a five-figure decision.
Converting a Class 10a shed to a Class 1a dwelling creates a new dwelling in the eyes of the code, and the energy provisions apply to it. In practice that is harder than a new build, because you have inherited a wall and roof system that was never designed to hold heat, and you are often retrofitting insulation into a portal frame with minimal cavity depth. Slab edge insulation is usually impossible after the fact. We have documented conversions that reached compliance and we have advised clients to stop and build new instead, and the decision usually turns on the existing structure’s frame and the climate zone. In zone 7 the arithmetic rarely favours the conversion.
Continue Your Research
House Extension Cost 2026: A Realistic Guide to Building Costs
1 Bedroom Granny Flats WA Price List 2026: Real Costs for a Perth Ancillary Dwelling
Shed to Granny Flat Conversion 2026: What You Need to Know
Draftee provides architectural drafting and documentation services. We are not builders, energy assessors, certifiers, or lawyers, and nothing above is legal, planning, or construction advice. Costs are indicative ranges observed on projects across New South Wales, Victoria, Queensland, and Tasmania during 2025 and 2026, and they will vary with your site, your climate zone, your trades, and material lead times. National Construction Code provisions, state adoption dates, transitional arrangements, and government fees have changed several times since NCC 2022 was published, and a Tasmanian amendment affecting residential provisions was in progress at the time of writing. Verify current requirements with your council, your registered certifier or building surveyor, and your accredited energy assessor before you lodge anything or commit money.
Last updated and changelog
Last updated: 19/8/2026
Changelog:
– 19/8/2026: Initial publication
