Building Classes Explained: NCC Class 1 to 10 in Australia

A building class is a single line on a certificate that quietly sets most of your construction budget. It decides the fire rating of your structure, whether you need a lift, how many accessible sanitary facilities you provide, which practitioners are legally allowed to design and build the job, what certificate you need before anyone can occupy the building, and in some states whether you have to lodge a bond before you can even apply for the occupation certificate.

The person who holds the answer is your building surveyor or certifier. They determine the classification, they carry it through the approval, and they are the ones who will tell you if the use you have drawn does not match the class you have assumed. The architect proposes, the certifier determines, and the appropriate authority has discretion where the call is genuinely unclear. Getting that conversation right early tends to be cheaper than getting it right at construction certificate stage.

Figures, section numbers and adoption dates in this guide were current at the date of writing and they move. Every rule here links to the primary source, which is where to confirm the position on your own project.

What is a building class under the National Construction Code?

A building class is a category the National Construction Code (NCC) assigns to a building or part of a building based on the purpose it is designed, constructed or adapted to be used for. There are ten headline classes, labelled Class 1 through Class 10, several with sub-classifications shown as a letter after the number, such as Class 1a or Class 7b.

The classification is not a label you pick. It follows from use. As Part A6 of the National Construction Code (NCC) puts it, the National Construction Code (NCC) “groups buildings and structures by the purpose for which they are designed, constructed or adapted to be used, assigning each type of building or structure with a classification”.

The class then routes you to a volume of the code:

• Volume One of the National Construction Code (NCC), which is the Building Code of Australia (BCA) for Class 2 to Class 9 buildings.
• Volume Two of the National Construction Code (NCC), which is the Building Code of Australia (BCA) for Class 1 and Class 10 buildings.
• Volume Three, which covers plumbing and drainage for every classification.

That split matters commercially because Volume One is a substantially heavier document than Volume Two. A townhouse row that lands in Class 1a is assessed against Volume Two. Put a common basement carpark under the same townhouses and they generally become Class 2, which pushes the whole job into Volume One and a materially different cost base.

Classification is also a risk-grading exercise rather than a naming exercise. The explanatory material in Part A6 of Volume Two describes it as “a process for understanding risks in a building or part, according to its use”, and says appropriate authorities deciding an unclear case look at what the building most closely resembles, the likely fire load, and the likely consequences of risks to the safety, health and amenity of people using it.

Why does the building class matter to a property developer?

Because it is the single input that fans out into the largest number of cost, programme and approval consequences, and because it is fixed before you have much ability to change it.

The class could reasonably be expected to drive:

Construction cost. Fire resistance level, construction type, sprinklers, fire hydrants, smoke control, sound insulation between dwellings, lift provision and accessible sanitary facilities are all keyed to class. A Class 2 apartment building and a Class 5 office of the same gross floor area do not build for the same rate, and neither does a Class 7b warehouse. If you are benchmarking, our guide to construction cost per square metre sets out how those typology rates behave.

Which practitioners you can engage. In New South Wales, Class 2, Class 3 and Class 9c work sits inside a registration regime and only registered practitioners can prepare regulated designs, make compliance declarations and lodge them. In Victoria and Queensland, the certifier or building surveyor you appoint must hold a class of registration that covers your building.

Which completion certificate you need. Some classes need an occupancy permit or a certificate of occupancy before anyone can lawfully use the building. Others do not. That is a real date on your settlement programme, not a formality.

Warranty, bond and insurance obligations. Residential classes attract consumer protection regimes that commercial classes do not. In New South Wales a strata apartment building attracts a building bond lodged before the occupation certificate application.

Accessibility. Whether the Commonwealth Premises Standards for access to buildings apply, and to which parts of a building, is expressed in building classes.

None of that is negotiable once the use is set, which is why the class is worth resolving at concept design rather than at the point where drawings go out to tender.

What are the ten building classes?

The table below is the short version. Every entry is drawn from Part A6 of the National Construction Code (NCC), and the detail underneath each class is where the developer consequences sit.

Class 1: houses, and the Class 1b line that catches short-stay

Class 1a is one or more buildings which together form a single dwelling, either a detached house or one of a group of two or more attached dwellings, each being a building separated by a fire-resisting wall. The National Construction Code (NCC) lists the row house, terrace house, town house and villa unit in that group.

Two limits matter. First, a Class 1 building cannot be located above or below another dwelling or another class of building, other than a private garage. Second, the code is explicit that a sole-occupancy unit used for residential purposes located over another sole-occupancy unit used for residential purposes “will always be a Class 2 or Class 3 building”. Stacking is the trigger, not height. The National Construction Code (NCC) notes that the number of storeys of a Class 1 building makes no difference to its classification.

Class 1b is where developers of accommodation product tend to get caught. It covers two quite different things:

• a boarding house, guest house, hostel or the like that would ordinarily accommodate not more than 12 people and has a total area of all floors of not more than 300 square metres, measured over the enclosing walls; or
• four or more single dwellings located on one allotment and used for short-term holiday accommodation.

The second limb has no floor area limit at all. The National Construction Code (NCC) explanatory material says that if four or more single dwellings are on one allotment and used for short-term holiday accommodation, each single dwelling would be Class 1b “regardless of the floor area of each dwelling or the combined floor area of all of the dwellings”. That is the classification most cabin-based holiday and tourist park product sits in.

The 12-person and 300 square metre thresholds are the ones to watch on a small hostel or co-living scheme. Exceed either and the Class 1b concession falls away, and the building is generally assessed as Class 3, which is a different code volume and a different cost base. The National Construction Code (NCC) explains the concession exists because “the smaller size of the building and its lower number of occupants represents reduced fire risks”.

Class 2: apartments, and the most heavily regulated class in the country

A Class 2 building is one that includes more than one dwelling, each generally solely occupied by one or more people to the exclusion of others, and which is not otherwise Class 1, Class 3 or a Class 4 part.

Two points catch people out. Class 2 buildings can be single storey attached dwellings: where there is any common space below such dwellings, they are Class 2 and cannot be Class 1, irrespective of whether the space below is a storey or not. And Class 2 buildings can be attached to buildings of another class, need not be attached to one another, and need not be more than a single storey.

That first point is the townhouse-over-basement trap. A row of ground-level dwellings sitting over a shared basement carpark generally reads as Class 2 rather than Class 1a, which changes the code volume, the fire and sound separation requirements, the accessibility position in common areas, and in New South Wales the entire practitioner registration and bond regime described further down.

Class 2 also carries the livable housing provisions. The Building and Plumbing Commission in Victoria sets out the position that the National Construction Code (NCC) 2022 livable housing requirements came into effect on 1 May 2024 and apply to dwellings (Class 1a) and within apartments (Class 2 sole-occupancy units), through Section G7 of Volume One and Part H8 of Volume Two. Adoption and variation of those provisions is a matter for each state and territory, so the position on your project depends on where it is.

Class 3: the accommodation class that is not Class 1 or Class 2

Class 3 covers residential accommodation for unrelated people where the length of stay is unimportant. Part A6 lists a boarding house, guest house, hostel, lodging house or backpacker accommodation, the residential part of a hotel or motel, the residential part of a school, accommodation for the aged, children or people with disability, the residential part of a health-care building accommodating staff, the residential part of a detention centre, and a residential care building.

The National Construction Code (NCC) explanatory material also brings dormitory accommodation, bed and breakfast accommodation, buildings housing elderly people or others requiring special care, and workers’ quarters including shearers’, fruit pickers’ or hotel workers’ accommodation into Class 3.

Where Class 2 and Class 3 genuinely blur, the code says the quiet part out loud. The Part A6 explanatory text acknowledges “a fine line between a Class 2 building containing apartments or flats and a Class 3 motel building with units containing bathroom, laundry and cooking facilities, which may both be made available for short term holiday rental”, and says an assessment will generally be based on the most likely use of the building by appropriate authorities. It then adds that Class 3 occupants “are generally unfamiliar with the building and have minimum control over the safety of the building”, represent a higher risk level, and require higher safety levels, so where the classification is unclear the decision should be made according to the perceived risks.

For anyone building serviced apartments, student accommodation or hotel product, that is the paragraph to read twice. It is also the reason the answer tends to move towards the more onerous class rather than away from it.

Class 4: the single dwelling inside a commercial building

Class 4 is a dwelling in a Class 5, 6, 7, 8 or 9 building where it is the only dwelling in the building. The classic case is a caretaker’s flat, or accommodation over or connected to a shop.

The constraint is strict. A Class 4 part cannot sit inside a Class 1, Class 2 or Class 3 building, and there can only ever be one Class 4 dwelling in a building. Add a second dwelling and both generally become Class 2 or, depending on use, Class 3. The National Construction Code (NCC) gives the worked case directly: where a Class 4 part is rented out it keeps its Class 4 classification, but if the attached shop is converted into an additional flat, both flats become classifiable as Class 2 or possibly Class 3.

On a mixed-use site with a manager’s residence, that is a live risk. One dwelling is a Class 4 part inside a commercial building. Two is an apartment building, with everything that follows.

Class 5 to Class 8: offices, shops, carparks, warehouses and factories

Class 5 is an office building used for professional or commercial purposes. The National Construction Code (NCC) lists professional chambers or suites, lawyers’ offices, government offices, advertising agencies and accountants’ offices.

Class 6 is a shop or other building for the sale of goods by retail or the supply of services direct to the public. The code brings in eating rooms, cafes, restaurants, the dining room or bar area that is not an assembly building, shops and kiosks in hotels and motels, hairdressers, public laundries, showrooms, sale rooms and service stations. Service stations are specifically Class 6, though the explanatory material notes that a building solely used for panel beating, auto electrical, muffler replacement or tyre replacement should be classified as Class 6, Class 7 or Class 8 “as the appropriate authority sees fit”.

Class 7 splits in two. Class 7a is a carpark. Class 7b is a building used for storage, or for the display of goods or produce for sale by wholesale.

Class 8 is a laboratory, or a building in which the production, assembling, altering, repairing, packing, finishing or cleaning of goods or produce for sale takes place. The National Construction Code (NCC) points out that laboratories, “despite their often small size, have been included as Class 8 buildings principally because of their high fire hazard”.

The Class 6 and Class 7 boundary trips up wholesale and trade-counter formats regularly. The code’s rule of thumb is blunt: Class 7 buildings include those used to sell goods on the wholesale market, whereas Class 6 buildings sell to the public, and “if the general public has access to the building, it is considered a ‘shop’, and therefore a Class 6 building”. If your trade supplies tenant plans a retail counter, the tenancy could be reading as Class 6 rather than Class 7b, which changes egress, sanitary facility and accessibility provisions.

Class 9: health care, assembly and residential care

Class 9a is a health-care building, including any parts set aside as laboratories, and includes a health-care building used as a residential care building. Note that laboratories inside a Class 9a building stay Class 9a, despite the general rule that laboratories are Class 8.

Class 9b is an assembly building. The National Construction Code (NCC) list is broad: theatres, cinemas, halls, churches, schools, early childhood centres, kindergartens, preschools and child-minding centres, indoor sports centres and stadiums, nightclubs, bar areas providing live entertainment or containing a dance floor, snooker halls, and bus and railway stations.

Class 9c is a residential care building. The code explains the class exists to recognise that “many residents progress through a continuum of care needs from low to high”, and that the classification allows any mix of low and high care residents and is intended to allow the mix to change over time “without the need to obtain any further consent or approval from the appropriate authority”. For an operator, that operational flexibility is the substance of the class, and it is why the code warns that building to Class 3 or Class 9a “may restrict the options available to the operators of a facility in relation to the profile of the residents they wish to accommodate”.

For anyone modelling an aged care asset, that flexibility could be a valuation-relevant point rather than a code footnote, because the resident mix feeds occupancy risk and occupancy risk feeds the income line.

Class 10: garages, sheds, fences, pools and bushfire shelters

Class 10a is a non-habitable building including a private garage, carport, shed or the like. Class 10b is a structure that is a fence, mast, antenna, retaining wall, free-standing wall or swimming pool or the like. Class 10c is a private bushfire shelter.

Two useful points. There is no requirement for a Class 10 building to be attached to a building of any other class, so a standalone shed or a toilet block in a park can be Class 10. And a habitable outbuilding cannot be Class 10: the code says a sleepout on the same allotment as a Class 1 building is part of the Class 1 building, as is a detached entertainment room, while a small toolshed used for non-commercial hobbies would be Class 10.

Some states and territories exempt certain Class 10 buildings and structures from needing a building permit, generally on the basis of height or size, and the National Construction Code (NCC) directs queries on that to the relevant state or territory body.

How is a classification determined, and who decides?

Classification follows the purpose the building is designed, constructed or adapted for, and the determination sits with the appropriate authority, in practice your building surveyor or certifier.

Where the class is unclear, the National Construction Code (NCC) says appropriate authorities have discretion. They look at what the building most closely resembles, the likely fire load, and the likely consequences of risks to safety, health and amenity. They may also consider relevant court decisions or determinations of the state or territory appeals body, though the code notes those determinations, and in some jurisdictions certain court decisions, “are usually not precedent creating” and are decided case by case.

There is one more layer worth knowing about: state and territory building regulators issue their own advice, interpretations and guidelines on classification, and the code recommends practitioners seek advice from the relevant authority. A national code does not always produce a national answer.

For a developer, the practical consequence is that the classification is an opinion formed by a professional, exercised under discretion, on facts you supply. The facts you supply are the intended use. If the intended use in the development application, the intended use in the lease or sales contract, and the intended use put to the certifier are not the same thing, that gap eventually surfaces.

What happens when a building has more than one class?

A building or part of a building may have more than one classification, and where it does, the more stringent requirements apply.

The National Construction Code (NCC) is explicit at A6G12 that each part of a building, including the entire building, may have more than one classification, so it is permissible to classify part of a building as Class 6/7 or Class 5/6 or whatever is appropriate. The code even anticipates the commercial reason: it expects a builder uncertain of the precise use of a building after sale, or wanting to maximise flexibility of use, may take this approach.

Dual classification is a real tool for speculative commercial product, because it buys leasing flexibility without a change of use later. It is not free. Under the Application to A6G12, where a building has more than one classification, the more stringent class requirements apply, so you are building to the higher standard across the dual-classified area.

That trade sits squarely in the feasibility. Extra capital cost now against a wider tenant pool and less re-fit risk later. Where the leasing outcome is uncertain, it tends to be a decision worth modelling both ways rather than resolving on instinct.

Where does the 10 per cent minor-use concession apply?

Where a part of a building has been designed, constructed or adapted for a different purpose and is less than 10 per cent of the floor area of the storey it sits on, the classification of the other part of the storey may apply to the whole storey.

The National Construction Code (NCC) gives the arithmetic directly. If a single storey factory has an office taking up 8 per cent of the whole storey’s floor area, the entire building including the office can be classified as Class 8. If that office takes up 12 per cent, the office area must be Class 5 and the remainder Class 8.

Two limits. The concession does not apply where the minor use is a laboratory, a Class 9b early childhood centre, or a Class 2, 3 or 4 part of a building. And even where the concession is used, occupant numbers for the particular use still come from the relevant table in Volume One, and the lighting, equipment, occupancy and load profiles for the minor-use area must reflect the actual use for energy efficiency purposes.

There is a scale trap in there. On a very large floor plate, 10 per cent is a large absolute area, and the code flags that the concession area may be large even though the rest of the building ordinarily carries lower risk. Separately, plant rooms, machinery rooms, lift motor rooms and boiler rooms take the classification of the part of the building they are in, and the 10 per cent test does not apply to them.

On a typical industrial or large-format retail scheme, that single percentage can decide whether an office fitout is assessed under Class 5 provisions or absorbed into the Class 8 or Class 7b shell. Worth checking against the schedule of areas before the plans are locked, alongside your gross floor area and net lettable area reconciliation.

Which classes trigger the heaviest compliance load in New South Wales?

Class 2, Class 3 and Class 9c. Building Commission NSW confirms that Class 2, 3 and 9c buildings are currently regulated under the Design and Building Practitioners Act 2020 (NSW) and the Residential Apartment Buildings (Compliance and Enforcement Powers) Act 2020 (NSW).

The shape of the regime, on the regulator’s own description:

• The laws initially applied to Class 2 buildings and buildings with a Class 2 part. On 3 July 2023 both Acts expanded to certain new Class 3 and Class 9c buildings and buildings with a Class 3 or 9c part.
• Alteration, repair or renovation work on existing Class 3 and Class 9c buildings will be subject to the Design and Building Practitioners Act 2020 (NSW) from 1 July 2028. The Act continues to apply to building work on new and existing Class 2 buildings.
• Design, building and professional engineer practitioners must be registered to work on Class 2 and certain Class 3 and Class 9c buildings. Registered designs and design compliance declarations must be lodged on the NSW Planning Portal before building work is carried out.
• A certifier cannot issue an occupation certificate until all compliance declarations are lodged on the NSW Planning Portal, and the principal certifier must not issue one unless the building compliance declaration and all other required documents have been provided.
• Under the Residential Apartment Buildings (Compliance and Enforcement Powers) Act 2020 (NSW), developers must give notice of the date they plan to apply for an occupation certificate and may be required to pay the building work levy.

There are carve-outs worth knowing. From 1 July 2024, Building Commission NSW states that certain low-risk Class 3 buildings and Class 9 buildings containing a minor Class 3 part are exempt, including hotels, motels, and Class 9a or 9b buildings that include minor accommodation facilities where the Class 3 part is less than 10 per cent of the gross floor area. Hotels and motels are only exempt if no part of the building is subject to a strata scheme and none of it contains serviced apartments.

The registration classes also bite on scale. A low-rise building for these purposes means a Class 2, 3 or 9c building, or a building with a Class 2, 3 or 9c part, with a maximum gross floor area of no more than 2,000 square metres, excluding Type A and Type B construction. A medium-rise building means one limited to a maximum of three storeys, or four storeys where the ground level or first storey is a Class 7a carpark. If your scheme sits a metre either side of those lines, the pool of practitioners who can lawfully declare your designs changes with it, which could be a programme risk as much as a cost one.

The strata building bond, and what the class costs you in cash

Separately from the practitioner regime, the Strata Building Bond and Inspections Scheme requires developers of apartment buildings to lodge a building bond with the Secretary before an application is made for an occupation certificate. Building Commission NSW states the bond “is 2% of the contract price (or the prescribed percentage in the regulation)”, and that an amendment to the Strata Schemes Management Regulation 2016 has deferred the increase from 2 per cent to 3 per cent until 1 July 2028. The buildings covered can include carparks, common areas, and commercial and retail parts of a mixed-use scheme.

The bond is not a fee. It is capital held out of your cashflow across a defined inspection timetable: a building inspector appointed within 12 months of building work being finished, an interim inspection between 15 and 18 months, a final inspection between 21 and 24 months, and the bond payment process completed between two and three years after the work was finished. If there are no defects, the bond is returned.

A worked illustration, using round numbers:

• 24 apartments over a basement carpark, gross realisation $28,800,000 at an average $1,200,000 per apartment.
• Building contract price $17,500,000.
• Class 2 strata scheme, so the Strata Building Bond and Inspections Scheme applies. Bond at 2 per cent of the contract price is $350,000, lodged before the occupation certificate application.

That $350,000 sits outside the project for roughly two to three years after practical completion, in a period when most developers are trying to close out and release equity. Against a gross realisation of $28,800,000 it is a small number in margin terms. Against the cashflow at the point where the debt facility is being repaid from settlements, it can be a live constraint, which is an argument for carrying it in the development cashflow model as a timed line rather than a footnote.

Change one input and the picture moves. If the same envelope were delivered as a hotel that is not subject to a strata scheme and contains no serviced apartments, it would generally be Class 3, no strata scheme means no strata building bond, and Building Commission NSW’s stated exemption for hotels and motels from 1 July 2024 would be in play. The point is not that one is better. The point is that the class follows the use, the use is fixed by what you are actually building and selling, and the obligations follow the class whether or not they were in the original budget.

Class 2 residential also interacts with the home warranty regime, which is a separate scheme with its own thresholds. Our guide to home warranty insurance in New South Wales covers that side.

What does the building class change in Victoria?

In Victoria the class decides which completion document you need and how far a renovation drags an existing building into current standards.

At completion the relevant building surveyor issues one of two documents: an occupancy permit, for buildings that will be occupied, or a certificate of final inspection where an occupancy permit is not required. Which one your building needs turns on its class, and it is a question to put to the relevant building surveyor at building permit stage rather than at handover, because the answer sits directly in front of your settlement date. The occupancy permit route also carries essential safety measures conditions, which set the inspection, testing and maintenance obligations the building inherits on day one.

The alterations rules are the sharper edge for anyone buying existing stock. The Building and Plumbing Commission’s guidance on livable housing sets out how Building Regulation 233 works. Where the volume of proposed alterations, together with any other alterations completed or permitted in the preceding three years, exceeds 50 per cent of the original building volume, the entire building must be upgraded to comply with the livable housing provisions, except where the relevant building surveyor consents to partial compliance. And where an extension increases the floor area of the existing building by more than the lesser of 25 per cent or 1,000 square metres, the proposed extension must comply with the livable housing provisions.

The relevant building surveyor’s discretion is the variable. The Building and Plumbing Commission says the surveyor should consider whether full compliance would be reasonable, weighing the objectives in section 4 of the Building Act 1993 (Vic) including safety, amenity and cost-effective construction, and notes that requiring existing hallways to be widened or an existing toilet upgraded when they are not affected by the proposed alterations could be unreasonable due to significant cost imposition. Any consent to partial compliance must be documented through Form 18 and within the building permit.

For a value-add or repositioning play, that 50 per cent volume test is the number to model against before you commit. It is the difference between a targeted refurbishment and a whole-building code upgrade.

What does the building class change in Queensland?

In Queensland the class determines whether you need a certificate of occupancy and whether you have to display it.

Business Queensland sets out that under the Building Act 1975 (Qld), any building built after 1 April 1976 should have a certificate of occupancy with its building approval, and that this does not apply to a single detached house (Class 1a), a carport or a garage (Class 10). From 1 October 2020 the former certificate of classification, Form 11, was amended and renamed the certificate of occupancy.

The display obligation is class-based and enforceable. You must display a certificate of occupancy before a building can be used or occupied if the building is Class 1b to Class 9 and was completed after 1 July 1997. It should be displayed as near as practical to the main entrance, and where a building has more than one main entrance, at the entrance emergency services would normally use and where the fire indicator panel is located. It is an offence not to display it, or not to comply with the restrictions stated on it, and a financial penalty may follow.

The certificate itself records the building’s class, how the building can be used, ongoing maintenance requirements, fire safety and other special requirements. For a shopping centre or other large building with more than one classification, there may be more than one certificate, displayed either together near the main entrance or at each tenancy.

That last point is where the class becomes an asset management issue rather than a construction one. The certificate records how the building can be used. A tenant whose actual use has drifted from the certificated class is a compliance exposure sitting inside your income stream.

How do the other states and territories treat classification?

The classification itself does not vary. The National Construction Code (NCC) is a single national document adopted by each state and territory, so a Class 2 building is a Class 2 building in Perth, Hobart, Darwin, Adelaide and Canberra on the same definitions set out in Part A6.

What varies is the machinery bolted on top: the state Act under which the permit or certificate is issued, the registration classes of the surveyor or certifier who can act on your building, the completion document you need before occupation, and any state variations to the code. Some states publish variations to specific Part A6 clauses, and the code text itself carries them where they exist.

The practical approach is to treat the class as national and the consequences as local. Confirm with the building surveyor or certifier registered in the relevant jurisdiction, at concept stage, three things: the class or classes they expect to apply, the registration class they hold and whether it covers your building, and which completion certificate the project will need. Those three answers are usually enough to expose any state-specific problem while the design can still absorb it.

New South Wales, as described above, currently sits well ahead of the other jurisdictions on residential class regulation, largely as a consequence of the 2020 reform package. Anyone extending a New South Wales development template into another state should not assume the reverse, that a lighter regime means a lighter build. The code obligations are the same. The oversight regime is what differs.

Which classes trigger accessibility obligations?

The Commonwealth Premises Standards for access to buildings, made under the Disability Discrimination Act 1992 (Cth), express their scope in building classes. Part 2 of the Premises Standards sets out the buildings to which the Standards apply, and Part A4 of the Access Code deals with building classifications, read to align with the classifications in the National Construction Code (NCC).

The line that matters most for residential developers is where the Standards stop. The Building and Plumbing Commission’s guidance states that the accessibility provisions of Section D4 of the National Construction Code (NCC) 2022 do not apply within the sole-occupancy unit of a Class 2 building, but do apply to the common areas outside the sole-occupancy unit and to Class 3 and Class 9 buildings where people are accommodated. It also notes that the internal parts of a Class 2 sole-occupancy unit are not covered by the Premises Standards.

So on an apartment building you are generally looking at two separate regimes running in parallel: the Premises Standards and Section D4 outside the front door of each apartment, and the livable housing provisions inside it. They are not the same standard and they are not interchangeable. The Building and Plumbing Commission is direct that the livable housing accessibility requirements “are not comparable to the accessibility requirements of the Premises Standards”, and points out that the Australian Building Codes Board (ABCB) Livable Housing Design Standard states in its own scope that it is not intended to achieve equivalence with AS 1428.1.

For an amenity-heavy scheme such as build-to-rent, where the common areas are extensive and the operator carries the building for decades, that split is worth understanding before the common area schedule is set.

Where do developers most often get the classification wrong?

Five boundaries account for most of the trouble, and all five are use questions dressed up as design questions.

Class 1a or Class 2, on stacking and common space. Any dwelling above another dwelling is Class 2 or Class 3. Any attached dwellings with common space below, whether or not that space is a storey, are Class 2. Basement carparks under townhouses are the usual culprit.

Class 1b or Class 3, on the size threshold. The Class 1b concession for a boarding house, guest house or hostel is bounded at not more than 12 people and not more than 300 square metres of total floor area. Push past either and Class 3 requirements generally apply. Co-living and small hostel product frequently sits close to that line.

Class 2 or Class 3, on serviced and short-stay product. The code itself acknowledges the fine line and resolves unclear cases towards the perceived risk, which pushes towards Class 3. Serviced apartments and hotel-branded residential are the recurring cases.

Class 3 or Class 9c, on care. The distinction is about resident care needs and the operator’s flexibility to change the resident mix. The National Construction Code (NCC) warns that building to Class 3 or Class 9a may restrict the operator’s options on resident profile, which is an operating risk with a valuation consequence.

Class 6 or Class 7b, on public access. Public access makes it a shop. Wholesale-only makes it storage or display for wholesale. Trade counters and click-and-collect formats sit right on that boundary.

The common thread is that none of these is resolved by drawing. They are resolved by being honest about the use, early, with the certifier.

What does a reclassification or a change of use cost you?

Late reclassification is expensive because it lands after the design is coordinated and often after the contract is priced.

A shift from Class 1 to Class 2, or from Class 1b to Class 3, generally moves the building from Volume Two to Volume One of the National Construction Code (NCC). That can bring fire resistance levels, fire separation, sound insulation, egress provision, sanitary facilities and accessibility into scope at levels the design did not assume. In New South Wales it can also drag the project into the registered practitioner regime and, if a strata scheme is involved, the strata building bond.

The programme cost is often worse than the capital cost. Redesign, re-coordination, a revised construction certificate or building permit and a re-priced contract tend to be serial rather than parallel activities, and they sit on the critical path. How that flows through a development is set out in our guide to construction programming.

Change of use on an existing building carries its own version of the problem. A change of use generally triggers an assessment against current requirements for the new class, and in Victoria the alteration and extension thresholds described above can pull unaffected parts of the building into scope. On acquisitions, the question to put to the building surveyor during due diligence is not “what is it now” but “what does it become if we do what we intend to do with it”.

Does the building class decide the tax or planning treatment?

No. Three separate systems classify the same building for different purposes, and they routinely disagree.

• The National Construction Code (NCC) class governs technical building requirements and certification.
• The planning definition in the applicable planning instrument governs what use is permissible on the land and what approval pathway applies.
• The tax characterisation, including whether something is residential premises or commercial residential premises for GST purposes, is a separate question again decided under tax law.

A boarding house can be a defined land use under a planning instrument, a Class 1b or Class 3 building under the code, and a different thing again for tax. None of those answers determines the others. A common and expensive assumption is that a favourable planning outcome carries a matching building class, or that a Class 3 classification settles the GST treatment. It does not.

Where the tax side is in play, that is a question for your accountant against your actual facts, and our guide to GST and property development sets out what the questions are. Where the planning side is in play, the reforms changing what can be built on a given site operate entirely independently of the code classification.

How does New Zealand classify buildings instead?

New Zealand does not use the Class 1 to Class 10 system. It uses classified uses under clause A1 of the New Zealand Building Code.

The Ministry of Business, Innovation and Employment states that for the purposes of the Building Code, buildings are classified according to type in seven categories: housing, communal residential, communal non-residential, commercial, industrial, outbuildings and ancillary. Clause A1 is published in Schedule 1 of the Building Regulations 1992.

A building with a given classified use may also have one or more intended uses under the Building Act 2004, which is a separate concept that matters for change of use. Fire design in New Zealand works to its own risk groups again under the relevant acceptable solutions.

For an Australian developer moving across the Tasman, or a New Zealand developer reading Australian material, the mapping is loose rather than exact. Housing broadly covers what Australia treats as Class 1 and Class 2, and communal residential broadly covers what Australia treats as Class 3, but the boundaries and the technical requirements behind them are not equivalents. Anything relying on a translation between the two systems should be confirmed with a New Zealand building consent authority rather than assumed.

Which edition of the National Construction Code applies to your project?

The National Construction Code (NCC) 2022 is the edition currently adopted across Australia, with National Construction Code (NCC) 2025 rolling in on a staggered basis, and the class definitions in Part A6 are stable between editions.

The New South Wales ministerial release of 25 March 2026 states that the National Construction Code (NCC) 2025 “will be available for adoption by State and Territory Governments from 1 May 2026”, and that New South Wales will adopt it on 1 May 2027 after a 12-month transition period. That release also confirms New South Wales plans a number of variations, including giving apartment building owners undertaking remedial work the choice of waterproofing requirements from either edition, and that the new energy efficiency standards will not apply to the common areas of apartment buildings.

Adoption dates and variations in the other states and territories are set individually by each jurisdiction, so the edition governing your project depends on where it is and when work commences. Confirm the applicable edition and any state variations with your building surveyor or certifier before you price the job, because an edition change generally moves the energy efficiency and technical provisions rather than the classification framework, and it is the provisions that move the cost.

What to ask your building surveyor or certifier

These are the questions that decide the classification on your facts, which this guide deliberately does not attempt to answer for you.

On the classification itself

• What class or classes do you expect to apply to this building, and to which parts of it?
• Which volume of the National Construction Code (NCC) does that put us in, and what changes in the technical requirements as a result?
• Is any part of this scheme close to a classification boundary, and what design change would push it over?
• Are you proposing to use the 10 per cent minor-use concession anywhere, and where does that leave the affected areas for occupant numbers and energy efficiency?
• If we dual-classify any tenancies for leasing flexibility, which requirements become the more stringent ones we build to?
• What state or territory variations to Part A6 apply here, and has the regulator issued any interpretation relevant to this use?

On registration and who can act

• What registration class do you hold, and does it cover this building on gross floor area, storeys and construction type?
• Which of our consultants need to be registered for this class of building, and are they?
• If our gross floor area or storey count changes during design development, does that change who can lawfully declare the designs?

On the completion pathway

• Which completion certificate does this project need, and what must be lodged before it can be issued?
• What is the realistic lead time between practical completion and that certificate on a building of this class?
• Are there class-based display or ongoing maintenance obligations attaching to the certificate?

On existing buildings and change of use

• If we change the use of this building, what class does it become and what does that trigger?
• What proportion of the existing building would have to be brought up to current requirements, and on what test is that measured?
• Would you be likely to consent to partial compliance, and on what basis?

For your quantity surveyor

• Has the cost plan been built to the class the certifier is actually proposing, or to the class we assumed at concept?
• What is the cost delta between the two candidate classifications, split between structure and fire, services, and finishes?
• What allowance sits in the plan for accessibility provisions in common areas, and does it reflect the correct class?

For your lawyer

• Do the use provisions in our leases or sales contracts match the classification on the certificate?
• What is our exposure if a tenant’s actual use departs from the certificated class?
• On acquisition, what warranties are available on the accuracy of the existing certificate and the building’s current classification?