The short version
- Class 1b is a building class under the National Construction Code: a boarding house, guest house, hostel or the like with a total floor area of no more than 300 m² that ordinarily accommodates no more than 12 people.
- Anything bigger is Class 3, which brings commercial-grade requirements.
- A family home is Class 1a. Renting its rooms to four or more people without approval to change it to Class 1b can be an offence.
- In Victoria, Clause 52.23 lets a rooming house of up to 300 m², 12 residents and 9 bedrooms skip the planning permit if every condition is met. That’s why so many rooming houses have nine bedrooms.
What Class 1b means
The National Construction Code (NCC) sorts every building into a class, and each class has its own safety and construction requirements. Houses are Class 1. Within that:
- Class 1a is a single dwelling, such as a detached house or townhouse.
- Class 1b covers small shared accommodation.
- Class 3 covers larger shared accommodation, such as bigger boarding houses and backpacker hostels.
The Australian Building Codes Board puts it this way:
“A Class 1b building is a boarding house, guest house or hostel that has a floor area less than 300 m2 and ordinarily has less than 12 people living in it.”
Australian Building Codes Board, NCC building classifications
The NCC’s own wording is slightly more generous: the building must “ordinarily accommodate not more than 12 people” and have “a total area of all floors not more than 300 m2”. So a building of exactly 300 m², or with exactly 12 residents, still qualifies.
Go over those limits and the building becomes Class 3, with commercial-grade requirements that make a suburban project much more expensive.
Class 1b and rooming houses
“Rooming house” is a legal term under Victoria’s tenancy laws, not a building class. Tenants Victoria describes a rooming house as “a building or an apartment where one or more rooms are available to rent, and the total number of occupants is 4 or more people.”
So a rooming house is about how a building is used. Class 1b is about how it’s built. A small rooming house needs both: the building approved as Class 1b, and the rooming house registered with the council and run by a licensed operator. Our rules guide covers the registration and licensing side.
Whitehorse City Council puts the building side plainly: “Shared accommodation with a floor area of no more than 300m² and no more than 12 residents is classified as a Class 1b building by the Building Code of Australia (BCA).” It also warns that “Unauthorised conversion of a building (converting a building from Class 1a to Class 1b) may constitute an offence which can be prosecuted by Council or the police.”
Why so many rooming houses have nine bedrooms
The answer is in Victoria’s planning rules. Clause 52.23 of the planning scheme exempts a rooming house from needing a planning permit in most residential zones if all of its conditions are met. To use land as a rooming house without a permit:
- The total floor area of all buildings on the land “does not exceed 300 square metres, excluding outbuildings”.
- “No more than 12 persons are accommodated.”
- “No more than 9 bedrooms are provided.”
To build one without a permit, there are further conditions, including that bedrooms “can only be accessed from within the building”, that shared entry, kitchen and living areas are provided, and, in the General and Neighbourhood Residential Zones, that the minimum garden area is met.
Put the planning limits and the Class 1b limits together and you get the common design: up to nine bedrooms, up to 12 residents, and just under 300 m².
What Class 1b means in practice
A Class 1b building is designed for unrelated people living under one roof, so fire safety and separation matter more than in a family home. Your building surveyor will confirm exactly what the NCC requires for your design. On top of the building code, Victoria’s rooming house minimum standards set rules for room locks, heating, windows, power outlets, electrical safety checks, kitchens and laundries.
In our homes, that means interconnected smoke alarms and emergency lighting throughout, acoustic insulation between suites, digital locks on the front door and every suite, and fixed heating and cooling in every room. Each home is about 295 m² with nine self-contained suites. You can see the full specification on our rooming houses page.
Buying or converting an existing house
- Ask for the building permit and occupancy permit showing the building was approved as Class 1b.
- Check the council registration and look up the operator on Consumer Affairs Victoria’s public register.
- If it hasn’t been approved, get a building surveyor to price the upgrade before you buy. Converting can cost far more than it looks.
- Check the floor area, bedroom count and number of residents against the Class 1b and Clause 52.23 limits.
Questions
Is a rooming house the same as a boarding house?
The terms overlap. “Boarding house” is the building-code language, and “rooming house” is the term used in Victoria’s tenancy and licensing laws. A small rooming house in Victoria is typically built as a Class 1b building.
Can I have more than nine bedrooms?
You can, but you lose the Clause 52.23 planning exemption and will need a planning permit. More than 12 residents, or more than 300 m², also takes the building out of Class 1b and into Class 3, which is a much bigger compliance step.
Does a Class 1b building need a planning permit?
Not always. In most residential zones, a rooming house that meets every condition of Clause 52.23 doesn’t need one. A building permit for Class 1b is still required.
Sources
- National Construction Code 2022, Volume Two, Part A6 Building classification
- Australian Building Codes Board, NCC building classifications
- Victoria Planning Provisions, Clause 52.23 Rooming house
- Whitehorse City Council, Rooming house
- Tenants Victoria, Rooming houses
- Consumer Affairs Victoria, Rooming house minimum standards
- Consumer Affairs Victoria, Rooming house operators licensing scheme
Written by Keyspace Property
We find the land, arrange the build and manage purpose-built rooming houses for investors in Victoria. We’re paid by the builder, so we’re not independent. How we’re paid.
General information only, not financial, tax or legal advice. Figures from Keyspace feasibilities are projections based on the assumptions shown, not guarantees. Rules and rates are as at 26 September 2026; check them before you act, and get independent advice about your own situation.