How to Pass BASIX for a Granny Flat in NSW

Granny flats, or secondary dwellings, are one of the most popular projects in NSW. They are also one of the easiest to get wrong on compliance, because owners assume a small build means an easy BASIX. The certificate is required, and the targets still apply. Here is how to pass cleanly.

Yes, your granny flat needs BASIX

Any new secondary dwelling requires a BASIX Certificate covering the same three areas as a full home: energy, thermal comfort and water. Whether you go through the Complying Development pathway or a DA, the certificate is part of the package.

The challenges unique to small dwellings

Small floor areas have a high ratio of external wall and window to internal space, so they lose and gain heat quickly. A single poorly placed window can swing the thermal result. Compact plans also leave little room for large hot water systems or tanks, so the choices have to be deliberate.

The levers that work best

• Orientation. Put living areas and the main glazing to the north where the site allows.
• Glazing. Keep windows modest and well-shaded, and use better glass on west-facing openings.
• Insulation. Good ceiling and wall insulation is cheap and highly effective at this scale.
• Hot water. A heat-pump or instantaneous gas unit lifts the energy score in a small footprint.

Water without the bulk

Efficient fixtures, a water-efficient toilet and a small rainwater connection are usually enough to meet the water target without a large tank dominating a compact yard.

Frequently asked questions

Can I reuse the main house BASIX for the granny flat? No. The secondary dwelling needs its own certificate based on its own design.

Is a granny flat cheaper to assess? Often, yes, because the design is simpler, but the targets are the same as any dwelling.

Building a secondary dwelling? Send us the plans and we will get your granny flat compliant fast.