BASIX for Townhouses and Multi Dwelling Housing in NSW

Townhouses, villas and other multi dwelling housing projects in NSW generally need BASIX as part of the residential approval pathway. These projects can be more complex than a single dwelling because the assessment may need to account for multiple homes, different orientations, shared walls, common areas, central services, private gardens and shared infrastructure.

The NSW Planning Portal describes multi dwelling housing as more than one dwelling on a single lot, including townhouses, villa units and dual occupancy. BASIX also has a multi dwelling assessment section designed for larger residential developments, especially where common areas, car parks, lifts and shared gardens can use significant water and energy. NSW Planning Portal

What counts as multi dwelling housing in BASIX?

Multi dwelling housing generally means multiple dwellings on one lot of land, whether attached or detached, with each dwelling having access at ground level. NSW Planning gives examples such as dual occupancy, villas, attached houses, townhouses and secondary dwellings associated with a new primary dwelling. Development can also be strata titled and include common areas and common infrastructure. NSW Planning Portal

This means a townhouse row, villa development or low-rise multi dwelling project is usually not assessed like a single stand-alone home. The project may need to be entered as multiple dwellings and assessed with dwelling-by-dwelling inputs, plus any shared or common area commitments.

How BASIX project type selection works

BASIX project type selection is important because it affects how the assessment is set up. NSW Planning explains that for multi dwelling housing, users enter the number of dwellings where there is more than one dwelling on a single lot, including townhouses, villa units and dual occupancy. For example, if there are four townhouses on one lot, the user enters four. NSW Planning Portal

This is why the assessor needs to know how the development is structured. A project with four dwellings on one lot may be entered differently from four separate single dwellings on four separate lots. If the project type is selected incorrectly, the BASIX Certificate may not match the approval pathway.

Does one BASIX Certificate cover all townhouses?

For new dwellings, NSW Planning states that the applicant must submit one BASIX Certificate covering all dwellings with the development application. In some cases, the consent authority may allow a project to be split and accept separate BASIX Certificates for different parts of the project. NSW Planning Portal

For townhouse projects, this means the project team should not assume each dwelling automatically receives a separate certificate. The correct approach depends on how the development is being lodged and whether council or the relevant consent authority accepts a split approach.

What BASIX assesses in townhouse projects

BASIX still assesses water, energy use and thermal performance, but townhouse and multi dwelling projects often require more detailed inputs because there are multiple dwellings. Each dwelling may have a different layout, orientation, window exposure, roof area, garden area, wall construction or system arrangement.

The assessment may need to include:

• Number of dwellings and project type.
• Floor areas and layouts for each dwelling.
• Window sizes, glazing, orientation and shading for each dwelling.
• Wall, roof, ceiling, floor and insulation details.
• Private garden areas, shared gardens and common landscaped areas.
• Hot water, heating, cooling and ventilation systems.
• Rainwater tanks, stormwater systems and alternative water sources.
• Solar PV, batteries or other alternative energy commitments.
• Pools, spas, lifts, car parks or common area services where relevant.

Why shared systems matter

Townhouse and multi dwelling projects may include shared systems or central systems. NSW Planning explains that BASIX assesses central systems and common areas in multi dwelling developments, including central hot water, central cooling, central heating, alternative energy sources, lifts, pools, spas and other measures. NSW Planning Portal

These shared systems need to be documented clearly because they may affect more than one dwelling or common area. If a central hot water system, shared rainwater tank or common solar system is proposed, the BASIX assessment needs to reflect how that system serves the development.

Central water tanks and shared water systems

Central water tanks can be important in multi dwelling projects. NSW Planning explains that a central water tank can be used in a multi unit development to supply water to common area uses, such as landscaping, car washing bays or cooling towers, or to more than one dwelling for private garden watering, toilet flushing or laundry. A central tank can collect rainwater or stormwater. NSW Planning Portal

The multi dwelling tool can also allow certain shared facilities and services, such as a shared rainwater tank, to be nominated as shared between dwellings. BASIX then apportions water use between individual and common areas and checks whether enough alternative water is available to reach the required water target.

Central hot water and energy systems

Some townhouse and multi dwelling projects may use central hot water or shared energy systems. NSW Planning describes a central system or facility as a system or facility that services more than one dwelling. BASIX assesses the energy used by central hot water and other central systems in multi dwelling developments. NSW Planning Portal

If central hot water or shared energy systems are proposed, the project team should provide enough information for the assessor to understand the system type, fuel source, distribution, dwelling allocation and whether the commitment can be delivered in the final design.

Garden areas and common landscaped areas

Garden areas can affect BASIX water calculations. For townhouse projects, this can include private courtyards, shared gardens, common landscaped areas and any areas irrigated by rainwater or other alternative water sources. The plans should clearly show the areas included in the development.

If garden areas are not clear, the water section may need further information. This is especially important where the BASIX outcome relies on rainwater tanks or central water systems to supply irrigation or other outdoor water uses.

Thermal performance in townhouse rows

Thermal performance can vary between dwellings in the same townhouse row. An end townhouse may have more exposed external walls than a middle townhouse. One dwelling may have west-facing glazing, while another may have a more favourable orientation. Shared walls, roof forms, floor construction and shading can all affect the final NatHERS or BASIX thermal comfort outcome.

This is why each dwelling should be represented accurately in the assessment. If one dwelling performs poorly, it may need better glazing, improved insulation, additional shading or other changes before the overall project can meet the required performance outcome.

Common BASIX issues in townhouse projects

Townhouse and multi dwelling projects often delay BASIX when the drawings do not clearly explain how each dwelling and shared system works. Common issues include:

• Incorrect project type selection.
• Plans that do not clearly identify each dwelling.
• Window schedules that do not separate dwelling types.
• Unclear shared walls, roof forms or construction systems.
• Central hot water or shared water systems not documented clearly.
• Garden and common area calculations missing or unclear.
• Solar PV commitments without enough roof area or allocation clarity.
• Plans changing after the BASIX Certificate has already been prepared.

What documents are needed?

For townhouse and multi dwelling BASIX assessments, the assessor needs enough information to understand each dwelling and any shared systems. The more clearly the drawings separate the dwellings, dwelling types, common areas and central systems, the smoother the assessment will usually be.

Useful documents and details include:

• Project address and approval pathway.
• Site plan showing all dwellings, private open space, common areas and access.
• Floor plans for each dwelling or dwelling type.
• Elevations and sections for the full development.
• Roof plan showing roof areas, solar opportunities and rainwater catchment.
• Window schedule or glazing details by dwelling or dwelling type.
• Construction and insulation details for walls, roofs, ceilings and floors.
• Hot water, heating, cooling and ventilation details.
• Rainwater tank, central water, solar PV, pool, spa or lift details, where relevant.
• Any strata, common property, central service or shared infrastructure information.

How Certified Energy can help

Certified Energy prepares BASIX Certificates and NatHERS assessments for townhouses, villas and multi dwelling housing projects across NSW. Our team can review the plans, confirm the likely BASIX pathway, identify missing information and coordinate the assessment across multiple dwellings and shared systems.

This is especially useful for townhouse rows, villa developments, low-rise multi dwelling projects and projects with central systems, shared rainwater tanks, common gardens, multiple dwelling types or tight thermal comfort requirements.

Related resources

• Complete Guide to BASIX Certificates in NSW
• BASIX Certificate Service
• BASIX for Dual Occupancies in NSW
• Rainwater Tanks and BASIX: When Are They Needed?
• Common BASIX Mistakes That Delay Approval

Frequently asked questions

Does BASIX apply to townhouses in NSW?

Yes. Townhouses are residential development and generally require BASIX in NSW. The NSW Planning Portal describes multi-dwelling housing as more than one dwelling on a single lot, including townhouses, villa units and dual occupancy.

What is multi dwelling housing in BASIX?

In BASIX, multi dwelling housing generally means multiple dwellings on one lot of land, including townhouses, villa units and dual occupancy. Each dwelling has ground level access and the development may include common areas or shared infrastructure.

Can townhouses share BASIX systems?

Yes. Multi dwelling projects may include shared systems or central systems, such as central water tanks, central hot water, alternative energy sources, lifts, pools, spas or other common area systems. These must be documented clearly for BASIX.

What documents are needed for townhouse BASIX?

An assessor usually needs the project address, site plan, floor plans for each dwelling, elevations, sections, roof plan, window details, construction and insulation details, garden areas, common areas, hot water, rainwater, solar, pool, spa and any shared or central system information.