Not every renovation needs a BASIX certificate. In NSW, BASIX for alterations and additions depends on two thresholds: the estimated cost of the work, and the size of any new pool or spa.
The two thresholds
| Trigger | Threshold | Notes |
|---|---|---|
| Alterations and additions to a dwelling | $50,000+ | Based on the estimated cost of development in your application |
| Swimming pool and/or spa | 40,000 L+ | Combined volume. Applies even if the pool is the only work |
If your work meets either threshold, a BASIX certificate must be lodged with the DA or CDC. If it’s under both, BASIX doesn’t apply, although council may still have its own sustainability controls.
How the $50,000 is worked out
The figure is the estimated cost of the development you nominate in the application, not what you end up paying. It should be a genuine estimate of the building work, usually from a builder’s quote or cost estimate. Understating it to avoid BASIX will cause problems when council or the certifier checks the cost.
- Work that forms one project is counted together. Splitting a renovation into smaller applications to stay under the threshold isn’t a workaround.
- A new granny flat isn’t an alteration. It is a new dwelling and needs its own BASIX certificate whatever the cost.
- A knockdown-rebuild is a new dwelling, not an alteration.
What gets assessed
The alterations and additions assessment focuses on the parts you’re changing, not the whole existing house:
- Thermal performance: insulation to new or altered walls, floors, ceilings and roofs, and the type, size and shading of new windows, doors and skylights.
- Water: new fixtures such as showerheads, toilets and taps, and rainwater tanks where included.
- Energy: new hot water systems, air-conditioning and lighting where they’re part of the work.
- Pools and spas: pool pump, heating and pool cover, where a pool is included.
Big glass extensions at the back of a house, such as bi-fold doors and a raked ceiling with highlight windows, are the usual problem. If the new work faces west, get it checked before the drawings are finished.
DIY or simulation for renovations?
Most alterations use the DIY thermal method. BASIX applies fixed insulation and glazing requirements to the new work. It’s quick and cheap.
A NatHERS simulation can be worth it when an extension has a lot of glazing. The DIY rules can force expensive glass upgrades that a simulation would show aren’t needed once eaves, orientation and thermal mass are taken into account. We check which route is cheaper before we start.
Common questions
My renovation is internal only. Do I need BASIX?
If the cost is $50,000 or more, yes. An internal renovation can still include new fixtures, hot water or lighting. The certificate will be simple, but it’s still required.
I’m doing a CDC, not a DA. Is it different?
No. The same thresholds apply, and the certificate goes in with the CDC application.
Can I use an old BASIX certificate?
The certificate must be current when you lodge. Generally it needs to have been issued no more than three months before the application is made, and it must match the plans you’re lodging. If the design has changed, it needs revising.
What to send for a quote
- Existing and proposed floor plans, with the new work clearly shown
- Elevations and sections of the new work
- The estimated cost of the work
- Details of any pool, including its volume, and any new hot water or air-conditioning
Renovating? Get a BASIX quote from your plans
Assessments prepared from your drawings, anywhere in NSW. Turnaround is confirmed in your quote and starts once all required information is received.
General information only, current at the date above. Requirements change and every project is different, so confirm the rules that apply to your project with your certifier or council.