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Building Classifications Explained

Buildings and structures are classified according to their use and classification also provides an understanding of risk in a building.

The following provides details and examples of the various classifications of buildings as provided in the National Construction Code (NCC).

Class 1 buildings

There are two types of Class 1 buildings:

Class 1a is a single detached dwelling (house) or can also be one or more attached dwellings that will share a common wall (party wall). These can include row houses, terrace houses, townhouses or villa units.

A Class 1b building is a smaller boarding house, guest house or hostel that may be commonly referred to as a ‘bed and breakfast’ accommodation that cannot accommodate more than 12 people and the floor area cannot exceed 300m2.

A Class 1b also includes four or more single dwellings located on one allotment and used for short-term holiday accommodation.

The main difference between a Class 1a and Class 1b is the fire safety requirements in that a Class 1b has more stringent provisions around smoke alarms and also requires a level of disability access.

It is important to note that a single dwelling that is located above another classification of building other than a private garage is not a Class 1 building which is explained below.
Also if you have a single dwelling with habitable outbuildings they are also part of the Class 1a dwelling, for example a ‘sleep out’ in the backyard.

Class 2 buildings

A Class 2 building is generally a building containing two or more sole occupancy units such as an apartment building and each sole occupancy unit is a single dwelling. 

A ‘sole occupancy unit’ is a room or other part of a building for occupation by one or joint owner, lessee, tenant, or other occupier to the exclusion of any other owner, lessee, tenant, or other occupier. A sole occupancy unit can include a dwelling such as in a Class 2 building or rooms or suites in other building classifications.

Another ‘type’ of Class 2 building can be where there is a single dwelling that is either attached to another dwelling alongside or a separate dwelling that is above another building classification other than a private garage.

An example of this is where a row of townhouses is built over a common carpark that is shared by the residents of the townhouses. The common carpark is another classification of building and not a private garage so this triggers a Class 2 classification for the townhouses. (see Figure 1)

Figure 1. Class 2 building where single detached dwellings are located over a common carpark

Class 1 or class 2?

It can be difficult at times to determine if a building is simply a dwelling or another type of residential building.

This is highlighted between Class 1 and Class 2 buildings and here are some scenarios:

Granny flats

Granny flats are quite common in Australian back yards and are generally ancillary dwellings.

Ancillary dwellings are small self-contained dwellings located on the same allotment as the main house or Class 1 building.

They usually contain some facilities like small kitchens and bathrooms that allow occupants to live independently from the main house but if they contain all the facilities required by the NCC to be a Class 1 building they may require planning approval to place two Class 1 buildings on the same allotment.

Some jurisdictions do allow granny flats to be placed with full facilities and are generally termed ‘dependant persons units’ and are intended to house an aged relative or the like; there may also be size limits.

These often do not require planning approval but will be approved with the condition that they are removed or ‘de-commissioned’ when they cease being used as a dependent persons unit.

Either way a granny flat is a detached part of the main class 1 building on the site.

‘Fonzie flat’

A ‘Fonzie flat’ is generally an ancillary dwelling built above a private garage associated with an existing Class 1 dwelling.

There are things to consider in relation to this type of ancillary dwelling.

Similar to Granny flats if the ‘Fonzie flat’ contains full amenities as required by the NCC to be a Class 1 dwelling then this may in some jurisdictions trigger the need for planning approval as you are effectively creating another Class 1 dwelling on the same allotment.

Otherwise this type of flat would be considered ancillary to the Class 1 and thus carry a Class 1 classification.

It would not be a Class 2 building as it is situated above a private garage and not another Class of building.

Townhouses with common (party) walls

As previously noted a Class 1 dwelling can be a row of townhouses with adjoining or common walls (party walls).

There is no limitation on how many dwellings can be attached this way as long as they do not have another class of building below or above them apart from a private garage (Class 10) then they remain a Class 1 building.

2 storey townhouse with a separate residence on the ground floor

In this case the classification is a Class 2 due to the fact that there are separate dwellings above and below.

The dwellings would have separate entries and there is fire separation requirements.

As previously noted even though they are both similar to a townhouse they carry more risk due to the fact that unrelated persons reside in each dwelling.

The diagram below shows a situation where a Class 2 building can still have private garages (Class 10) but the is still a Class 2 because it has a dwelling above another separate dwelling.

Mixed development – Class 2 and Class 1 example

Modern land development may cater for both apartment and single dwelling living and this is where you might have both apartments and Class 1a single dwellings on the same new housing estate.

In this case due to the design of the estate there may be a multi-storey apartment building with a common carpark within the building which makes it a Class 2 building.

There may also be stand-alone or separate single dwellings as a row of townhouses with separate or detached parking for each townhouse.

In this case the single dwellings would still be 1a single dwellings even though the parking is provided separately.

There may be some jurisdictional issues around providing the parking this way and each State and Territory will have building regulation requirements around how car parking is provided but this does not change the classification of the building as long as the use remains the same (single dwelling).  

Class 3 buildings

A Class 3 building is a residential building other than a Class 1 or 2 that serves as a common place for long term, or transient living for a number of unrelated persons.

This includes boarding houses, guest houses backpackers’ accommodation etc., residential parts of motels and hotels, residential parts of schools, detention centres and accommodation for the elderly and persons with a disability, to name a few.

It’s important when looking at the building classifications in the NCC that you check the definition of any italicised words (which indicate there is a definition for that word) as this will expand the scope of a building classification.

For example a Class 3 can be a residential part of a health-care building and a health-care building can include a hospital, nursing home, or a day clinic or surgery which is described in the definitions section of the NCC. 

Class 2 or class 3?

There is 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. 

When does a Class 3 motel unit become a Class 2 holiday flat and vice versa?

In general, an assessment will be based on the most likely use of the building by appropriate authorities (generally the certifier or building surveyor issuing the building approval).

Class 3 buildings, where the occupants are generally unfamiliar with the building and have minimum control over the safety of the building, represent a higher risk level and therefore require higher safety levels.

In a case where the classification is unclear, a decision should be made according to the perceived risks inherent in the use of the building.

Class 4 buildings

A Class 4 building is simply a dwelling contained in a Class 5,6,7,8,or 9 building as long as it’s the only dwelling in the building.

A common example may be a dwelling that is over or connected to a shop.

A Class 4 cannot be located in a Class 1, 2, or 3 building

Class 5 buildings

A Class 5 building is an office building used for professional or commercial purposes. A Class 5 could be a lawyers or accountants office or a government office.

Class 6 buildings

A Class 6 building is where goods are sold directly to the public, generally a shop. 

Class 6 buildings include cafes and restaurants, dining rooms and bar areas (as long as the bar area is not an assembly building or a Class 9b building) a hairdressers or barbers shop, supermarkets and also service stations.

Service stations under this classification are generally not intended to cover buildings that provide for example tyre replacement, panel beating or an auto electrician. These buildings should be classified as Class 6, 7 or 8 buildings as the appropriate authority (generally the building surveyor or certifier) sees fit.

Class 7 buildings

There are two classifications for a Class 7 building.

A Class 7a building is a carpark. A carpark is defined in the NCC as: a building that is used for the parking of motor vehicles but is neither a private garage nor used for the servicing of vehicles, other than washing, cleaning or polishing. 

Figure 1 shows separate dwellings above a common carpark and this carpark is a Class 7a building as it’s not a private garage.

A Class 7b can have two uses, it can either be a building used for storage or as a ‘warehouse’ or can be a building used to display of goods or produce for sale by wholesale.

Class 8 buildings

Class 8 Buildings are ‘process type’ buildings or factories.

They include laboratories, and buildings used for production, assembling, altering, repairing, packing, finishing, or where cleaning of goods or produce for sale takes place.

Even very small laboratories are included as a Class 8 building because of high fire hazard risk.

Class 8 buildings include food manufacture but not restaurants that are Class 6 buildings.

Other Class 8 buildings are potteries and farm or horticultural buildings where goods are processed or packaged.  

Class 9 buildings

Class 9 buildings are buildings of a public nature. 

Class 9 buildings have three classifications.

A Class 9a is a health-care building and as noted previously a ‘health-care building’ is defined in the NCC and can include hospitals, nursing homes and day clinics or surgeries. A health-care building can include parts of the building set aside as laboratories. 

A Class 9b is an assembly building including a trade workshop or lab in a primary or secondary school but excludes any other parts of the building that are another class.

‘Assembly building’ is defined in the NCC and includes buildings used for:

  • civic, theatrical, social, political or religious purposes including a library, theatre, public hall or place of worship
  • educational purposes in a school, early childhood centre, preschool, or the like
  • entertainment, recreational or sporting purposes including:
    • discos
    • nightclub or a bar areas of a hotel or motel providing live entertainment or containing a dance floor
    • cinemas
    • sports stadiums and clubs; or

A Class 9c building is a residential care building.

It is defined in the NCC as a Class 3, 9a or 9c building which is a place of residence where 10% or more of persons who reside there need physical assistance in conducting their daily activities and to evacuate the building during an emergency (including any aged care building or residential aged care building) but does not include a hospital.

Class 10 buildings

A Class 10 is a non-habitable building or structure.

There are three classifications for Class 10 buildings- Class 10a buildings include sheds, private garages (as opposed to carparks) carports and the like.

It is important to note that for example if you change a Class 10a shed that is associated with a Class 1 house into a habitable building (you may fit it out as a sleep out) then it effectively becomes part of the Class 1 building and should satisfy the requirements, where relevant, of the house.

The diagram below from the NCC clearly describes this situation where you have a Class 1, detached part of a Class 1 (sleep-out) and a Class 10 building on an allotment.

A Class 10b is a structure that is a fence, mast, antenna, retaining wall or free-standing wall or swimming pool or the like.

A Class 10c is a Private Bushfire Shelter associated with a Class 1a building and is defined in the NCC as: 

Private bushfire shelter means a structure associated with, but not attached to, or part of a Class 1a dwelling that may, as a last resort, provide shelter for occupants from immediate life threatening effects of a bushfire.

Mixed use buildings

What if a building has more than one use?

It is common for buildings to have multiple classifications or be ‘mixed use’.

For example a city apartment building may contain retail shops below and a basement carpark making this a building with Class 2, Class 6 and a Class 7 carpark.

Each part of a building must be separately classified however if a part that has a different use is not more than 10% of the floor area of the floor that it’s on it may be considered ancillary to the main classification and can adopt the main classification.

Multiple classifications

A building (or a part of a building) may be designed to serve multiple purposes and may have more than one classification.

This means that a building may be intended for multiple uses such as office space, storage or a shop.

This allows flexibility in how the building might be used and as long as the design of the building meets all the requirements for each classification a building can carry multiple classifications.

This can also assist the building designer at the design stage as it may not be clear who the final tenant will be or how they will be using their tenancy.

Who classifies buildings?

It is generally the job of the relevant certifier or building surveyor to classify the building when they are assessing it for building approval.

Obviously the building designer should be designing a building according to its use and should understand what the classification of the building is but as noted previously this can be subjective.

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