In NSW, a BASIX certificate is needed for every new home, for renovations (alterations and additions) to a dwelling costing $50,000 or more, and for a new swimming pool or spa of more than 40,000 litres. The NSW Planning Portal’s BASIX page sets out those three triggers. BASIX, the Building Sustainability Index, is required under State Environmental Planning Policy (Sustainable Buildings) 2022 and sets standards for water, energy and thermal performance. Increased standards came into effect on 1 October 2023. The certificate is generated online through the Planning Portal and must accompany the DA or complying development application. Its commitments, from insulation and glazing to rainwater tanks and fixtures, then become conditions that must be built and certified before the occupation certificate. For home owners, the most common mistake is assuming a renovation is “too small” for BASIX, or changing windows on site after the certificate was issued.
Key takeaways
- A BASIX certificate is required for new dwellings, for alterations and additions to a dwelling costing $50,000 or more, and for a pool or spa of more than 40,000 litres.
- BASIX is required under State Environmental Planning Policy (Sustainable Buildings) 2022 and covers water, energy and thermal performance; the standards were increased from 1 October 2023.
- The certificate is generated using the BASIX tool on the NSW Planning Portal and is lodged with the DA or CDC; the plans must show the commitments.
- BASIX commitments become conditions of consent and must be installed and evidenced before the occupation certificate.
- If the design changes after the certificate is issued, a revised BASIX certificate is usually needed, and sometimes a modification of the consent.
Who this is for: home owners planning an extension, second storey, major internal renovation or pool in Sydney, the Central Coast or regional NSW, who want to know whether BASIX applies and how to avoid delays at DA, construction certificate and occupation certificate stages.
When does a renovation need BASIX?
The NSW Planning Portal states that you need a BASIX certificate if you are building a new home, renovating for $50,000 or more, or installing a pool or spa of more than 40,000 litres. In practice:
| Project | BASIX needed? |
|---|---|
| New house, dual occupancy, granny flat or townhouse | Yes, always |
| Extension or renovation of a dwelling with an estimated cost of $50,000 or more | Yes (alterations and additions certificate) |
| Renovation under $50,000 | No |
| New pool or spa over 40,000 litres | Yes |
| Garage converted to a secondary dwelling | Yes, as a new dwelling |
| Non-residential work, such as a shed with no habitable space | No |
The cost is the estimated cost of the development stated in the application. Splitting a renovation into two applications to stay under $50,000 is not a sensible strategy; councils compare the scope with the cost estimate and will question an estimate that looks low.
What does BASIX measure for alterations?
BASIX assesses three areas: water, energy and thermal performance. For alterations and additions, the focus is typically on the new or altered parts of the dwelling. The thermal section looks at insulation, glazing, shading and construction of the new work. The energy section looks at items such as hot water systems, lighting and appliances being installed. The water section looks at fixtures and any rainwater tank. The Planning Portal’s BASIX help notes for the project details, water, thermal performance and energy sections explain each input.
The increased standards that commenced on 1 October 2023 apply to new applications. If you prepared a design years ago and are only now lodging, the certificate must be generated under the current tool, and the design may need adjusting to pass.
How BASIX fits into the approval steps
- Design. Settle window sizes, glazing types, insulation and the hot water system with the designer, because these drive the thermal and energy results.
- Generate the certificate. Use the BASIX tool on the Planning Portal (an applicant account is required), or have a BASIX or NatHERS assessor prepare it where a thermal simulation is used.
- Show commitments on plans. Councils and certifiers check that the plans match the certificate: window schedules, insulation notes, tank sizes.
- Lodge with the DA or CDC. The certificate must be issued no earlier than three months before lodgement under the usual rules; check with your certifier or council.
- Construction certificate. The certifier confirms the CC plans are consistent with the BASIX commitments.
- Build and evidence. Keep invoices and installers’ certificates for insulation, glazing, hot water and fixtures.
- Occupation certificate. The principal certifier must be satisfied the commitments have been fulfilled.
Where renovations go wrong with BASIX
The first is the window swap. The builder substitutes a cheaper window with a different glazing specification, or the owner enlarges a window during construction. The built work no longer matches the certificate, and the OC stalls. The second is the hot water system. A renovation certificate that relied on a heat pump cannot be satisfied with a standard electric storage unit. The third is the missing certificate for a pool. Pools over 40,000 litres need BASIX in their own right, even where the house is not being altered. The fourth is cost estimates. An estimate deliberately kept under $50,000 that the council considers unrealistic can lead to a request for a revised estimate and a BASIX certificate.
The fix in each case is the same: treat BASIX commitments as part of the specification, and update the certificate before changes are made, not after.
Definitions
- BASIX
- The Building Sustainability Index, the NSW system setting water, energy and thermal performance standards for residential development.
- BASIX certificate
- The certificate generated through the Planning Portal listing the commitments a development must meet, lodged with the DA or CDC.
- Alterations and additions
- Renovation work to an existing dwelling; a BASIX certificate is required where the estimated cost is $50,000 or more.
- BASIX commitments
- The specific measures, such as insulation levels, glazing, hot water systems and fixtures, that must be built and installed.
- State Environmental Planning Policy (Sustainable Buildings) 2022
- The State policy under which BASIX requirements apply to residential development in NSW.
Frequently asked questions
Does my renovation need a BASIX certificate?
If it is an alteration or addition to a dwelling with an estimated cost of $50,000 or more, yes. Below that, a BASIX certificate is not required.
Does a swimming pool need BASIX?
A new pool or spa of more than 40,000 litres needs a BASIX certificate.
Can I change my windows after getting BASIX?
Only with care. If the change affects the BASIX results, a revised certificate is needed, and if the approved plans change, possibly a modification of the consent.
Who prepares a BASIX certificate?
Anyone with a Planning Portal applicant account can generate one using the BASIX tool, but many owners use a designer or an accredited assessor, particularly where a thermal simulation is used.
We check BASIX triggers and commitments as part of every renovation Statement of Environmental Effects and DA package we prepare. For BASIX certificates and thermal assessments, our sister company NathersPro can help. For your extension or renovation DA, request a fee proposal.
Sources and references
- NSW Planning Portal, BASIX, accessed October 2026
- NSW Planning Portal, Increases to BASIX standards (from 1 October 2023), accessed October 2026
- NSW Planning Portal, BASIX support materials and help notes, accessed October 2026
- State Environmental Planning Policy (Sustainable Buildings) 2022, Chapter 2, accessed October 2026
Information disclaimer. This article is general planning information prepared by the URBA Planning Team and is current at the date of publication. It is not planning, legal or financial advice for any specific property. Planning instruments, development control plans, state policies and the National Construction Code are amended regularly and councils interpret them differently; the controls quoted here should be confirmed against the versions in force at the date of lodgement and against the consent authority’s current requirements. Reliance on this article is at the reader’s own risk. URBA Planning, a division of Contrive Consultants Pty Ltd, accepts no liability for loss arising from its use. For advice on a specific site, contact URBA for a fee proposal.