BASIX for Mixed Use Developments in NSW

Mixed use developments in NSW can require more than one energy or sustainability compliance pathway. If the project includes residential apartments or dwellings, BASIX will usually apply to the residential component. If the same building also includes retail, office, restaurant, commercial or other non-residential areas, those areas may require a separate NCC energy efficiency pathway such as Section J.

The key point is that BASIX should not automatically be assumed to cover the entire mixed use building. BASIX requirements apply to residential dwelling types in NSW and cover water, energy use and thermal performance. Non-residential floor areas need to be identified clearly so the project team can confirm whether BASIX, Section J or both are required for the approval package. NSW Planning defines non-residential floor area as floor area used for non-residential purposes, including retail, office and restaurant areas. NSW Planning Portal

What is a mixed use development?

A mixed use development combines different uses within the same building or site. In a NSW residential energy compliance context, this often means apartments above retail, residential units above offices, shop top housing or a building that contains both residential and commercial floor areas.

For BASIX, the important question is which parts of the development are residential dwellings and which parts are non-residential. The residential component may need BASIX. The non-residential component may need a different assessment pathway, usually connected to the National Construction Code and Section J energy efficiency requirements.

Does BASIX apply to the whole building?

BASIX does not necessarily apply to the whole mixed use building. It applies to the residential dwelling component. NSW Planning states that BASIX requirements apply to all residential dwelling types in NSW and form part of the development application process. BASIX covers water, energy use and thermal performance for residential development. NSW Planning

If the building includes retail shops, offices, restaurants, commercial tenancies or other non-residential floor area, those spaces may need to be excluded from the residential BASIX assessment and reviewed through the correct commercial energy compliance pathway. This is why the plans should clearly separate residential and non-residential areas before the assessment starts.

When does Section J apply?

Section J is the energy efficiency part of the National Construction Code that is generally used for commercial and other non-residential building areas. In a mixed use development, Section J may apply to the retail, commercial, office, restaurant, childcare or other non-residential components, while BASIX applies to the residential apartments or dwellings.

This is why mixed use projects often need both residential and commercial energy compliance advice. The two assessments may look at some similar design elements, such as glazing, insulation, services and lighting, but they are different pathways and should not be treated as interchangeable.

What BASIX assesses in the residential component

For the residential component of a mixed use development, BASIX assesses water, energy use and thermal performance. If the residential component is apartments or a residential flat building, the BASIX assessment may need to account for individual dwellings, apartment types, common areas, central services, shared gardens, lifts, car parks and residential plant systems.

The residential BASIX assessment may include:

• Number of residential dwellings or apartments.
• Residential floor plans and apartment schedules.
• Apartment layouts, glazing, orientation and shading.
• Wall, roof, ceiling, floor and insulation details.
• Residential hot water, heating, cooling and ventilation systems.
• Residential common areas, lifts, car parks and shared gardens.
• Central water tanks, central hot water, solar PV, pools or spas where relevant.

What may be outside BASIX

The non-residential part of the project may sit outside the BASIX assessment. NSW Planning defines non-residential floor area as floor area used for non-residential purposes, including retail, office and restaurant areas and associated areas such as storage areas and kitchens. It does not include common area that services both residential and non-residential parts, such as a lobby, carpark or loading bay. NSW Planning Portal

In practice, this means the project team needs to identify which areas are residential, which areas are non-residential and which areas are shared. This helps determine what belongs in BASIX, what belongs in Section J and what may need to be coordinated between the two.

Shared areas can create confusion

Mixed use buildings often include shared or overlapping areas, such as foyers, basement car parks, loading areas, plant rooms, stairs, lifts or service corridors. These areas can create confusion because they may serve both residential and non-residential parts of the building.

The plans should make these areas clear before assessment begins. If a car park, lobby, plant room or lift serves both residential apartments and commercial tenancies, the project team may need to confirm how it should be treated across the BASIX and Section J documentation.

Residential flat buildings in mixed use projects

Many mixed use projects include residential flat buildings above commercial ground floor spaces. For residential flat buildings, NSW Planning’s BASIX project type guidance says users enter the number of residential flat buildings and, for each building, the number of dwellings or apartments and the number of storeys. NSW Planning Portal

This information helps set up the residential BASIX assessment. However, it does not automatically resolve the commercial component. The retail, office or other non-residential spaces still need to be reviewed through the appropriate non-residential pathway.

Common mixed use BASIX issues

Mixed use BASIX delays often happen when the plans do not clearly separate residential and non-residential scope. Common issues include:

• Unclear residential and commercial floor area separation.
• Assuming BASIX covers the whole building.
• Forgetting that Section J may be needed for non-residential areas.
• Apartment schedules that do not match the architectural plans.
• Common areas, lobbies, car parks and lifts not clearly documented.
• Central services serving both residential and commercial areas without clear allocation.
• Retail or commercial glazing being confused with residential glazing.
• Late design changes affecting both BASIX and Section J assumptions.

Can one consultant prepare both BASIX and Section J?

In many cases, it is useful for one energy compliance team to review both the BASIX and Section J pathways. This can reduce confusion where glazing, insulation, services, common areas, plant rooms or mixed-use floor areas affect more than one report. It can also help keep the documentation consistent before lodgement.

However, the reports should still remain distinct. BASIX is the NSW residential sustainability certificate. Section J is the commercial energy efficiency compliance pathway. A coordinated team can help align the assumptions without merging the two into one document.

What documents are needed?

For a mixed use development, the assessor needs enough information to understand the residential component and the boundary between residential and non-residential areas. The more clearly the plans separate the uses, the easier it is to confirm whether BASIX, Section J or both are required.

Useful documents and details include:

• Project address and approval pathway.
• Site plan and full building plans.
• Clear residential and non-residential floor area separation.
• Apartment floor plans and dwelling schedules.
• Retail, office, restaurant or commercial tenancy plans.
• Elevations, sections, roof plan and glazing details.
• Construction and insulation details.
• Residential hot water, heating, cooling and ventilation details.
• Commercial services information, where available.
• Common areas, lifts, car parks, plant rooms and shared services.
• Rainwater, stormwater, central water, solar PV, pools or spas, where relevant.

How Certified Energy can help

Certified Energy prepares BASIX Certificates for NSW residential projects and Section J Reports for commercial and non-residential projects. For mixed use developments, our team can review the plans, identify the residential and non-residential components and confirm which assessment pathways are likely to be needed.

This is especially useful for apartment buildings with ground floor retail, shop top housing, residential developments with commercial tenancies, projects with shared car parks or plant rooms and developments where BASIX and Section J assumptions need to be coordinated before lodgement.

Related resources

• Complete Guide to BASIX Certificates in NSW
• BASIX Certificate Service
• BASIX vs Section J: Which One Applies?
• Section J Report Service
• BASIX for Apartments and Residential Flat Buildings in NSW

Frequently asked questions

Does BASIX apply to mixed use developments in NSW?

BASIX applies to the residential dwelling component of a mixed use development in NSW. The non-residential component, such as retail, office or restaurant areas, may require a separate NCC energy efficiency pathway such as Section J.

Does BASIX apply to commercial areas in a mixed use building?

BASIX is a residential sustainability assessment pathway. Commercial or non-residential areas of a mixed use building are generally not assessed through BASIX and may need separate commercial energy compliance, such as Section J.

Can a mixed use project need both BASIX and Section J?

Yes. A mixed use project may need BASIX for the residential apartments or dwellings and Section J for the retail, office, commercial or other non-residential parts of the building.

What documents are needed for mixed use BASIX?

An assessor usually needs the project address, site plan, residential floor plans, apartment schedules, elevations, sections, roof plan, glazing details, construction and insulation details, common area information, residential services, central systems and clear separation between residential and non-residential floor areas.