Understanding building classifications in NSW—and why they matter for your project

When you’re planning a new home, extension, multi-residential project, or commercial space, one of the first steps is understanding building classifications in NSW. It’s a key part of the National Construction Code (NCC), and it affects everything from design decisions to approvals, safety requirements, and who is allowed to work on your project.

Below, we break down how building classes work, what sets each class apart, why Class 2 is receiving so much focus today, and how Sorensen Design guides you through the process with clarity and confidence.

Why building classifications exist

The NCC categorises buildings by their primary use and assigns each a Class 1 to Class 10 rating, with some classes including sub-classes (e.g., Class 1a, Class 1b). These classifications set out the minimum technical requirements for safety, performance, and compliance for new buildings and building work in existing buildings.

A building may also contain one or more buildings or different parts with different uses. In these cases, each part may need its own classification.

Understanding your classification early ensures your design:

• Meets the right structural and fire-safety rules
• Complies with energy efficiency requirements
• Is approved faster through Council or a private certifier
• Can be documented correctly for your DA, CDC, or Construction Certificate.

Working with a qualified building designer ensures these details are resolved from day one.

Overview of building classifications in NSW

Below is a clear summary of the key classes found in the National Construction Code NCC, based on the definitions from the Australian Building Codes Board.

Class 1 buildings – houses and small-scale accommodation

Class 1 buildings are single dwellings of a domestic or residential nature. These include:

• Class 1a – a single dwelling, such as a detached house, or one of a group of attached dwellings like a townhouse, row house, terrace house, or similar.
• Class 1b – small-scale accommodation such as a boarding house, guest house or hostel under 300 m² with fewer than 12 occupants, or short-term holiday cabins on one allotment.

These buildings must be separated appropriately when attached, typically with a fire-resisting wall.

Class 2 buildings – apartments, multi-residential projects and regulated designs

Class 2 buildings are multi-unit residential buildings, where people live above and below one another. They typically include:

• Apartment buildings
• Multi-storey unit developments
• Mixed-use buildings with residential levels
• Single-storey attached dwellings above a shared space (such as a basement carpark).

In the NCC, each apartment is considered a sole-occupancy unit (SOU), and the building must provide the right fire separation, acoustic performance and structural systems to support multiple dwellings within one structure.

Why is Class 2 heavily regulated in NSW?

Class 2 developments fall under the Design and Building Practitioners Act 2020 (DBP Act).

This legislation was introduced to lift construction standards and ensure safer, more compliant residential buildings across NSW. As part of these reforms, certain parts of a Class 2 design are classed as Regulated Designs, which must be:

• Prepared by a registered Design Practitioner (like a building designer)
• Declared before work begins
• Lodged on the NSW Planning Portal
• Coordinated with other registered practitioners (structural, fire safety, waterproofing, etc.)

The NSW Government states that registered practitioners must take responsibility for the design, ensure it complies with the National Construction Code, and provide a Design Compliance Declaration before the builder can commence work.

What this means for your project

If you're planning an apartment building or mixed-use development with residential levels, you must engage a practitioner who is properly registered to design Class 2 buildings. This includes:

• Design of structural elements
• Fire-resisting construction
• External waterproofing systems
• Building layout and SOU configuration
• Any component listed by the NSW Government as a Regulated Design.

Failure to use a registered practitioner can delay approvals, expose the project to compliance issues, or prevent the builder from commencing work legally.

Our Class 2 capability

Sorensen Design is a registered Building Design Practitioner under the DBP Act. This means we are authorised to:

• Prepare Regulated Designs for Class 2 buildings
• Provide the required Design Compliance Declarations
• Coordinate documentation with other Design Practitioners
• Manage design obligations through the NSW Planning Portal
• Ensure your Class 2 project meets the NCC and all DBP Act requirements.

Our team works closely with certifiers, engineers and builders to ensure your Class 2 development is compliant, buildable and efficient, from early concept planning through to final approval.

Why professional Class 2 design matters

Class 2 buildings are more complex than detached homes or small additions. They require:

• Careful planning of shared structures and services
• Fire separation between SOUs and common spaces
• Acoustic performance in accordance with NCC Volume One
• Accessible pathways and compliance with common space requirements
• Detailed coordination between disciplines and approval bodies.

With the right certified building designer, you avoid rework, shorten approval timelines and protect the long-term integrity of the project. And for homeowners, developers and builders alike, the peace of mind is invaluable.

Class 3 buildings – larger residential accommodation

Class 3 buildings house multiple unrelated persons, often in a long-term or transient setting. Examples include:

• Larger boarding houses or guest houses beyond Class 1b limits
• Hostels and worker accommodation (e.g. shearers’ quarters)
• Dormitory-style accommodation
• Some care-type residential buildings not classified as Class 9.

These buildings require careful planning due to their shared facilities, occupant numbers, and evacuation needs.

Class 4 – a residence within another building

A Class 4 part is a sole dwelling within a non-residential building. Example: a caretaker’s residence in a storage facility.

Class 5 – office buildings

Class 5 includes buildings used for professional or commercial purposes, such as:

• Offices
• Professional services
• Government agencies
• Architectural or design firms.

These spaces have their own fire and access requirements and often form part of mixed-use developments.

Class 6 – retail, dining and hospitality

These buildings involve the sale of goods or services directly to the public, including:

• Shops and showrooms
• Restaurants and cafés
• Hairdressers and barbers
• Funeral parlours
• Public laundries
• Hotel dining rooms or bars.

Class 7 – storage and car parking

Class 7 buildings include:

• Class 7a – carparks
• Class 7b – storage buildings or wholesale display centres.

Class 8 – factories and workshops

These are industrial buildings used for production, assembly, repair, manufacturing or processing, such as:

• Factories
• Mechanic workshops
• Food-processing facilities (e.g. abattoirs).

Class 9 – public and care buildings

These are buildings of a public or care-related nature, broken into:

• Class 9a – health care buildings (hospitals, day surgery clinics, facilities where patients may need physical assistance)
• Class 9b – assembly buildings such as schools, universities, theatres, sports facilities, childcare centres
• Class 9c – residential care buildings, including aged care facilities where residents require daily personal or physical assistance.

Class 10 – non-habitable structures

Class 10 includes three sub-classes:

• Class 10a – sheds, private garages, carports
• Class 10b – structures including retaining walls, fences, masts, antennas, and swimming pools
• Class 10c – private bushfire shelters.

These are common additions to residential projects and still require the proper approvals and compliance path.

Mixed-use and multi-class buildings

A building may have multiple classifications if it serves different purposes. For example, a building with:

• A basement carpark (Class 7a)
• Ground floor retail (Class 6)
• Apartments above (Class 2)
• Office levels above that (Class 5)

According to the NCC (page 5), each part is classified separately and must meet the specific requirements of its respective class. This is especially common in urban and coastal NSW regions, where developments often serve multiple purposes.

Why building classifications matter for your project

Building classifications directly affect:

• Structural design
• Fire safety and evacuation systems
• Energy efficiency
• Accessibility requirements
• Whether your project requires a DA, CDC or Construction Certificate
• The level of documentation needed for compliance
• Which design and building practitioners are authorised to work on the project.

Choosing the wrong classification can lead to delays, redesigns, or non-compliance. Selecting the right one early keeps your project moving smoothly.

How Sorensen Design supports you through the classification process

As experienced building designers working across Port Stephens, Newcastle, the Hunter Region, Maitland, the Central Coast and Sydney, we help you:

#1. Identify the correct building class from the outset

We assess your project’s use, floor area, layout and occupant needs to determine the correct classification, whether it’s a single dwelling, Class 2 building, boarding house, storage building, or mixed-use development.

#2. Design to meet the NCC’s minimum technical requirements

Your drawings, documentation, and specifications are prepared to comply with the NCC and any local variations.

#3. Manage your approval pathway

We assist with:

• Development Applications (DAs)
• Complying Development Certificates (CDCs)
• Construction Certificates (CCs).

We also work closely with local Councils, private certifiers, engineers and other industry professionals.

#4. Reduce project risk

Clear classification leads to better design outcomes, safer buildings, and smoother coordination with builders and consultants.

#5. Provide specialist Class 2 expertise

Class 2 projects in NSW require designers who understand NCC Volume One, SOU layouts, common spaces, acoustic performance, fire separation and the requirements for design and building practitioners.

Sorensen Design has substantial experience in this area and offers complete support for Class 2 buildings.

Contact our team for specialist support with building classifications in NSW

Understanding building classifications in NSW is more than just a compliance box-ticking exercise. It’s the foundation of a safe, functional and approved design.

Each classification has its own requirements under the National Construction Code, and getting it right early protects your budget, timeline and design intent.

At Sorensen Design, we guide you through the entire process, from the initial conversation to final approvals. Our experienced team interprets the NCC, prepares compliant documentation, and designs spaces that work for the people who use them, whether it’s a single dwelling, a Class 2 apartment project, or a mixed-use development.

If you’re planning a residential or commercial build, we’re here to make the process clearer, easier and more predictable. Contact us today.