BASIX v4.04: What the May 2026 Tool Update Changes for Multi-Dwelling Projects
Multi-dwelling developers have long dealt with a genuine administrative headache under BASIX: managing separate certificates across a single development site. New BASIX changed that on 1 May 2026, alongside a handful of other updates that specifically matter for larger residential projects. This guide breaks down exactly what’s new in BASIX v4.04 for multi-dwelling developments, separate from the smaller changes that apply to single-home projects.
Why Multi-Dwelling Projects Needed a New BASIX Update
Before this update, a multi-dwelling development — whether a townhouse row, a duplex pair, or a larger apartment project — often needed multiple separate BASIX certificates managed individually, even when the dwellings were part of one coordinated development. This update addresses that directly, and it’s a genuinely developer-driven fix rather than a policy change, responding to a practical pain point rather than a new sustainability requirement.
The 1,000-Dwelling Certificate: What It Actually Means
The headline change in new BASIX is the ability to request up to 1,000 dwellings on a single BASIX Certificate, covering any mix of single dwellings, duplexes, townhouses, or apartments within the one development. For a large masterplanned project, this means one certificate can now track an entire staged release rather than dozens of individual ones, considerably simplifying both the initial application and any subsequent amendments across the site.
Materials Guidance for Shared-Building Developments
Multi-dwelling developments with separate buildings that share common areas — a common configuration for townhouse and apartment projects — now benefit from clearer guidance for completing the materials section under the update. Previously, this was one of the more ambiguous parts of a multi-dwelling application; the update specifically targets that ambiguity for developments with shared infrastructure spanning multiple buildings.
BASIX Thermal Performance Requirements: What Changed for Multi-Dwelling Projects
BASIX thermal performance requirements themselves haven’t changed in substance under this update — the underlying targets a multi-dwelling project must hit are the same as before. What has changed is the process: data is now retained when a project switches between the Simulation and DIY thermal performance methods, which matters more for multi-dwelling developments than single homes, since larger or more complex dwelling types within the same development often need to move to Simulation partway through design after starting on DIY.
Solar PV and Whole of Home BASIX Assessment for Multi-Dwelling Certificates
Certificates and reports for new homes now display full details of solar photovoltaic systems specifically for multi-dwelling projects, giving certifying authorities clearer visibility into how solar generation is allocated across a development. This sits alongside the broader whole of home BASIX assessment approach to energy — covering fixed appliances, hot water, and on-site generation collectively — which becomes more complex to track across many dwellings than for a single home, making this reporting improvement particularly useful for multi-dwelling teams.
All Electric Home BASIX Net Zero Considerations for Larger Developments
Many larger residential developments are now designed as all electric home BASIX net zero projects from the outset, avoiding gas connections entirely in favour of electric heating, cooling, hot water, and cooking — an approach that also aligns with the broader national direction on commercial and residential energy efficiency. The update’s expanded low-emissions concrete grade options and clearer multi-dwelling materials guidance both support this kind of development, since an all electric home BASIX net zero strategy typically pairs electrification with broader material and embodied carbon choices across a development, not just the energy system alone. Torple’s BASIX service can advise on structuring an all-electric multi-dwelling certificate from the outset.
Ventilation and Showerhead Changes That Apply to Every Dwelling
Two smaller technical changes under this update apply to every dwelling in a multi-dwelling project individually, not just the certificate as a whole: bathroom, kitchen, and laundry ventilation can no longer be directed into the roof space, and showerheads using 4.5 to 6 litres per minute now register as 5 stars. For a development with dozens or hundreds of dwellings, these per-dwelling changes need to be reflected consistently across every unit type in the design, not just checked once at a representative dwelling.
What This Means for Your Next Multi-Dwelling DA
For a multi-dwelling project heading toward a Development Application, this update makes the certification process itself more practical, without changing the underlying BASIX thermal performance requirements a design has to meet. The BASIX thermal performance requirements that applied under v4.03 carry over unchanged into v4.04, so no design already meeting the current BASIX standards needs revisiting on that basis alone. Torple’s NatHERS assessment service can confirm how thermal performance targets translate across a mixed dwelling-type development, and Torple’s 7-Star Energy Rating service covers the equivalent national standard for projects outside NSW. The most immediate action is deciding whether to consolidate an existing multi-certificate development onto the new single-certificate structure, and confirming the materials section documentation reflects the clearer shared-building guidance now available.
Final Thoughts
New BASIX v4.04 is squarely aimed at multi-dwelling developers, and the 1,000-dwelling certificate allowance alone justifies a second look at how a larger project’s BASIX documentation is structured. Torple’s BASIX assessment service can advise on consolidating a multi-dwelling development under the new certificate structure, and Torple’s Section J assessment service can assist where a development includes commercial or mixed-use components alongside the residential dwellings. Torple’s VURB assessment service covers the alternative Verification Method pathway where a mixed dwelling-type development includes non-standard designs. Torple’s Website has further reading on BASIX Compliance Certificate Updates for 2026, and Torple’s BASIX landing page covers the update’s other, non-multi-dwelling changes in more depth. For the official release notes, see the NSW Planning Portal, and for the BASIX tool itself, see basix.nsw.gov.au.
FAQ
New BASIX v4.04 is the version of the BASIX tool that took effect on 1 May 2026, replacing v4.03 with a range of functionality, flexibility, and technical changes, most significantly for multi-dwelling projects.
Up to 1,000 dwellings, covering any mix of single dwellings, duplexes, townhouses, or apartments within the same development, rather than requiring separate certificates for each dwelling type or stage.
No, the underlying BASIX thermal performance requirements a project must meet haven’t changed. What’s changed is that data now carries over when switching between the DIY and Simulation methods, which particularly helps multi-dwelling projects with mixed dwelling complexity.
Yes. The new 1,000-dwelling certificate structure applies regardless of energy strategy, and an all electric home BASIX net zero development can be consolidated onto a single certificate the same way any other multi-dwelling project can.
The whole of home BASIX assessment approach itself is unchanged, but certificates now show fuller solar PV details for multi-dwelling projects, making it easier to see how on-site generation is allocated across a development’s whole of home energy picture — a genuine improvement for teams managing whole of home BASIX assessment reporting across dozens of dwellings.
Confirm whether consolidating onto the new single certificate structure suits the project’s staging, check the updated materials section guidance for shared-building developments, and verify ventilation and showerhead specifications are updated consistently across every dwelling type.