Working on a Class 2 Building in NSW: What You Need to Know
“A Class 2 building is one containing two or more separate dwellings, most commonly an apartment block, where residents live above or below one another rather than side by side. In NSW these buildings carry extra obligations under the Design and Building Practitioners Act, including registered practitioners, declared designs and lodgement on the NSW Planning Portal before work starts.”
In New South Wales, any work on a Class 2 building – such as apartment buildings or multi-story residential dwellings with two or more units – must comply with the Design and Building Practitioners Act 2020 (DBP Act).
Engage Construction is fully registered to deliver compliant work on Class 2 buildings and can manage the entire process for you, from pre-construction planning to final declarations.
What is a Class 2 building in NSW?
A Class 2 building contains two or more sole-occupancy units, each of which is a separate dwelling.
"Sole-occupancy unit" is the National Construction Code term for a part of a building occupied by one person or household to the exclusion of others. In practice, a Class 2 building is almost always an apartment building: separate homes stacked above one another, sharing a structure, common property and services.
The vertical relationship is what usually decides it. Where one dwelling sits above another, you are generally looking at Class 2. Where dwellings sit side by side, each separated by a fire-resisting wall running to the underside of the roof, you are generally looking at Class 1a.
Mixed-use buildings matter here too. A block with retail at ground level and apartments above is not entirely Class 2, but the residential part is, and the compliance obligations attach to that part.
How Class 2 differs from the classes around it
The National Construction Code sorts buildings into ten classes. Three of them sit close enough to Class 2 to cause confusion.
Class 1a covers houses. That includes detached homes, and also terraces, townhouses and villa units where each dwelling is separated from the next by a fire-resisting wall and no dwelling sits above another.
Class 2 covers buildings of two or more separate dwellings, typically stacked. Apartment blocks. Some townhouse developments, where the arrangement puts one dwelling over another.
Class 3 covers residential buildings that are not Class 1 or Class 2: places where unrelated people live long term or transiently. Boarding houses, hostels, hotels, motels, some student accommodation and some residential care.
Class 4 covers a single dwelling inside a building that is otherwise commercial or industrial. A caretaker's flat above a shop is the classic example.
The distinction is not cosmetic. It determines fire separation, sound insulation, access and egress, and whether the DBP Act applies to your project at all.
Pre-Construction Compliance Checklist for Class 2 Buildings
Before any building work can start on a Class 2 building in NSW, there are strict compliance steps that must be completed under the Design and Building Practitioners Act 2020 (DBP Act). These steps ensure that all work is properly designed, declared, and approved before construction begins.
Here’s what must happen before any physical work starts on site:
1. Engage Registered Practitioners
You must appoint:
Registered Design Practitioners to prepare regulated designs (e.g. structural, waterproofing, fire safety)
A Registered Building Practitioner (like Engage Construction) to carry out the building work
These practitioners must be registered under the DBP Act through NSW Fair Trading. Search and verify NSW registered Design and Building practitioners licence and registration information.
2. Prepare and Declare All Regulated Designs
Each regulated element (e.g. structure, façade, fire systems) must have a design prepared and signed off by a Registered Design Practitioner.
Each designer must complete a Design Compliance Declaration, confirming that their design complies with the Building Code of Australia (BCA) and all relevant standards.
3. Lodge Designs on the NSW Planning Portal
All declared designs and declarations must be uploaded to the NSW Planning Portal before construction can start.
These lodgements become part of the permanent project record and are reviewed by NSW Fair Trading.
4. Builder Reviews and Declares Compliance
The Registered Building Practitioner (Engage Construction) must:
Review all lodged designs
Submit a Building Compliance Declaration on the Planning Portal
Confirm that we will build strictly in accordance with the declared designs
5. Certifier and Approvals (if applicable)
If an Occupation Certificate (OC) will be needed, you may also need to:
Appoint a Registered Certifier
Obtain a Construction Certificate (CC) or Complying Development Certificate (CDC)
Provide all documentation for pre-commencement approval
What happens when a design changes mid-build
Designs change during construction. Every variation to a regulated design needs its own Design Compliance Declaration and its own lodgement on the Planning Portal, the same as the original.
This is the step most often missed, because it lands mid-project when everyone is focused on the build rather than the file. The consequence surfaces at the end: if the building as constructed no longer matches the declared designs, the Building Compliance Declaration cannot honestly be made, and the Occupation Certificate waits.
Track variations as they happen rather than reconstructing them at completion.
Only After All of the Above Are Completed
Design declarations are submitted
Building declaration is lodged
All designs are on the NSW Planning Portal
(If required) Approvals and certificates are issued by your certifier
Then and only then can physical building works legally begin.
The Act followed a run of apartment defect failures in NSW that left owners carrying repair costs nobody had budgeted for. The paperwork exists so that when something goes wrong, there is a record of who designed what and who declared it compliant.
Why This Process Exists
These steps were introduced to:
Prevent poor-quality construction
Improve safety and accountability
Ensure projects are legally compliant from day one
Engage Construction can manage this entire process for you – coordinating designers, declarations, and lodgements to keep your project compliant and on track.
Why declarations get rejected
Most rejections come down to the same handful of problems.
The practitioner is not registered in the right category. Registration is specific. Someone registered for one class of design work cannot declare another.
The design set is incomplete. A declaration covers a design. If a required regulated design was never prepared, there is nothing to declare, and the gap surfaces at the worst possible moment.
Work started before lodgement. This cannot be fixed retrospectively. It can only be disclosed.
Variations were never re-declared. The building as constructed no longer matches the declared designs.
Documents do not match each other. Drawing numbers, revision numbers and dates that disagree across the set will hold up the whole lodgement.
None of these are complicated. They happen because the compliance work gets treated as administration to catch up on later, rather than as part of the programme.
FAQ
Is a duplex a Class 2 building?
Usually not. A standard duplex is two dwellings side by side, separated by a fire-resisting wall, with neither one above the other. That is Class 1a.
It becomes Class 2 when one dwelling sits above the other. If you are building or altering a duplex where the dwellings are stacked, check the classification before you go any further, because the compliance path is completely different.
Are townhouses Class 2 buildings?
It depends on the arrangement rather than the label. Townhouses in a row, each with its own footprint and separated by fire-resisting walls to the underside of the roof, are generally Class 1a.
Where a development stacks dwellings over one another, or where dwellings sit above a shared basement in a way that creates a common structure, Class 2 can apply. Strata subdivision on its own does not decide it. The physical arrangement does.
Is a Class 2 building a commercial building?
No. Class 2 is a residential classification. The confusion usually comes from the fact that Class 2 buildings are governed by NCC Volume One, the same volume that covers commercial buildings, while houses sit in Volume Two.
A Class 2 building can form part of a mixed-use development with commercial space in it, but the residential part remains residential.