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Building classes for shared housing
| Class 1a | A single dwelling — a detached house, or an attached dwelling separated by a fire-resisting wall[1] |
|---|---|
| Class 1b | Boarding house, guest house or hostel for not more than 12 people and not more than 300 m²; or four or more holiday dwellings on one allotment[1] |
| Class 3 | Residential building giving long-term or transient accommodation to unrelated people — larger boarding houses, hostels, dormitories, workers' quarters[2] |
| Class 9c | Residential care building where 10% or more of residents need physical assistance with daily activities and evacuation[2] |
| Which code volume | Class 1 houses: Volume Two. Classes 2 to 9: Volume One[1][3] |
Every building approved in Australia is given a class under the National Construction Code (NCC). The class follows from how the building is used, not how it is built, and it decides which set of technical requirements applies. The question arises when the same building will house people who are not one household — students renting rooms, seasonal workers, or several older people living with shared care.
The classes that matter for shared living §
| Class | What it covers | Typical shared-living example |
|---|---|---|
| 1a | A single dwelling: a detached house, or attached dwellings separated by fire-resisting walls[1] | A family home; a granny flat |
| 1b | Boarding house, guest house or hostel ordinarily accommodating not more than 12 people, with total floor area not more than 300 m²[1] | A house letting rooms; a small bed and breakfast |
| 2 | Apartment buildings, with units above and below each other[2] | Apartments |
| 3 | Long-term or transient accommodation for unrelated people, beyond the 1b limits[2] | Student residences, staff and workers' quarters, larger hostels |
| 9c | Residential care where 10% or more of residents need help with daily activities and evacuation[2] | Residential aged care |
Sharing does not automatically change the class §
The NCC's explanatory information makes a point that is often missed: a building shared by unrelated people who jointly own or rent it, or who share it with an owner or tenant, can remain a Class 1 building regardless of size.[1] A group of students on one lease of a whole house is a different use from an owner letting individual beds.
The move to Class 1b is a step, not a leap. The code allows Class 1b to take advantage of some Class 3 concessions so that people can rent rooms or run bed and breakfast accommodation without meeting full Class 3 requirements, but Class 1b still needs more smoke alarms than a house and, in some cases, disability access features.[1]
Beyond 12 people or 300 m², the building is in Class 3.[2] Class 3 sits in NCC Volume One, the volume written for Class 2 to 9 buildings, rather than Volume Two, which covers houses.[1][3]
Where the class comes up §
Large student residences and workers' quarters fall within Class 3 by definition[2] — see modular student accommodation. A household letting rooms is a different matter: rental thresholds that trigger boarding house and rooming house laws are covered in renting a granny flat to students.
For older people, a family home with a parent living in a granny flat is a Class 1 dwelling.[1] A building providing personal care to several unrelated older residents may be Class 3 or Class 9c depending on their care needs.[2] For homes designed to stay usable as residents age, see the Livable Housing Design Standard; for specialist disability housing, see NDIS SDA and modular construction.
If a factory-built home is intended for any use other than a single household, the intended use is a question to put to the builder and the building surveyor or certifier before the design is finalised, since the class decides which requirements the design is documented to.
What is not covered here §
This page does not set out the technical requirements that attach to each class — fire resistance, egress, sound insulation, smoke alarm placement or accessibility. Those are in the NCC and the referenced standards, and differ between editions.
It is based on NCC 2022 classification provisions. It does not establish whether NCC 2025 changed any classification wording, or how each state and territory has varied classification in its own adoption of the code. It does not cover planning law, which uses its own land-use definitions (boarding house, co-living housing, seniors housing) that do not map neatly onto NCC classes.
Classification of a specific building is made by the building surveyor or certifier. Nothing here is a classification decision or compliance advice.
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References §
- Australian Building Codes Board — NCC 2022 Volume Two, Part A6 — A6G2 — a Class 1 building is a dwelling. Class 1a is one or more buildings forming a single dwelling, such as a detached house or an attached dwelling separated by a fire-resisting wall. Class 1b is a boarding house, guest house, hostel or similar that would ordinarily accommodate not more than 12 people and has a total floor area of not more than 300 m², or four or more single dwellings on one allotment used for short-term holiday accommodation. Explanatory information: Class 1b can use some Class 3 concessions so people can rent rooms or run bed and breakfast accommodation without full Class 3 requirements; Class 1b needs additional smoke alarms and in some cases disability access; buildings shared by unrelated people who jointly own or rent them, or share with an owner or tenant, can be Class 1 rather than Class 3; a Class 1 building cannot be located above or below another dwelling. abcb.gov.au/editions/ncc-2022/adopted/volume-two/a-governing-requirements/part-a6-building-classification
- Australian Building Codes Board — NCC Navigator, building classifications — Class 2 is apartment buildings of sole-occupancy units with people living above and below each other. Class 3 is residential buildings other than Class 1 or 2 where unrelated people live for long or short stays, including boarding houses, guest houses, hostels and backpackers larger than the Class 1b limits, dormitory-style accommodation, workers' quarters, and care-type accommodation for children, the elderly or people with disability unless classed as Class 9. Class 9c is residential care buildings where 10% or more of residents need physical assistance with daily activities and with evacuation in an emergency, such as aged care buildings providing personal care. nccb.gov.au/ncc-navigator/building-classifications
- Australian Building Codes Board — NCC 2022 Volume One — Volume One is the Building Code of Australia for Class 2 to 9 buildings. cpd.nccb.gov.au/editions/ncc-2022/adopted/volume-one/preface/introduction-ncc-volume-one
Figures are as published by the sources above at their respective dates and are paraphrased summaries, not verbatim reproductions. Verify current pricing and rules directly with builders, lenders and planning authorities.