Compliance

Confirmed against a NSW Government source

• Minimum lot area

  Sourced

  The lot must be at least 450 m² for a secondary dwelling under the Housing SEPP.

  NSW Planning — Housing SEPP, secondary dwellings
  checked 2026-09-06

• Minimum lot width

  Sourced

  The lot's boundary with the primary road, measured at the building line, must be at least 12 m (for a lot of 450-900 m²), 15 m (over 900-1,500 m²), or 18 m (over 1,500 m²). A battle-axe lot needs an access laneway at least 3 m wide, measuring at least 12 m by 12 m excluding the laneway. FIXED 2026-09-12: this was previously stated as a flat 12 m for every lot size, which understates the requirement on larger lots and could show a fail lot as passing.

  Housing SEPP 2021, Schedule 1, cl 2(1)(b)-(c)
  checked 2026-09-12

• Maximum floor area

  Sourced

  A secondary dwelling approved as complying development is capped at 60 m² internal floor area.

  NSW Planning — Housing SEPP, secondary dwellings
  checked 2026-09-06

• Permitted zones

  Sourced

  Secondary dwellings are permitted in residential zones R1, R2, R3, R4 and R5. A council's own LEP may permit them in other zones as well.

  NSW Planning — Housing SEPP, secondary dwellings
  checked 2026-09-06

• No subdivision

  Sourced

  A lot with a secondary dwelling cannot be subdivided. The result must be exactly one principal dwelling and one secondary dwelling on the site.

  NSW Planning — Housing SEPP, secondary dwellings
  checked 2026-09-06

• Bushfire (BAL)

  Sourced

  A BAL rating between 12.5 and 29 does not rule out the CDC pathway, provided the dwelling is designed to AS 3959 for the applicable BAL. Above BAL-29, expect the DA pathway.

  NSW Planning — complying development / Housing SEPP
  checked 2026-09-06

• CDC determination time

  Sourced

  A Complying Development Certificate is determined by a registered certifier or council against fixed standards, not a discretionary merit assessment, and can be issued in as little as 20 days. CORRECTED 2026-09-12: this previously said there is no neighbour notification — that's wrong. Neighbours within the notification area are still given a pre-approval notice (commonly 14 days in metro areas) and a pre-construction notice (7 days metro / 2 days regional) before work starts; only the full DA merit-assessment step is skipped, not notification.

  NSW Planning Portal — complying development / neighbour notification
  checked 2026-09-12

Applies to you, but not yet confirmed here

These are real requirements — they are not optional and they are not edge cases. What this site does not yet do is state their specific numbers, because those numbers vary by council and had not been confirmed against a primary source at the time of writing. The eligibility indicator excludes them entirely rather than assuming they pass.

• Setbacks

  Confirm yourself

  Front, side and rear setback minimums apply and vary by lot size and council. The specific distances for your lot must be confirmed against your council's LEP/DCP and the Housing SEPP.

• LEP floor-area variation

  Confirm yourself

  Outside the complying-development pathway, the Standard Instrument LEP allows a maximum secondary-dwelling floor area of the greater of 60 m² or a percentage of the principal dwelling's floor area. The exact percentage and how your council applies it must be confirmed.

• Fire separation (attached secondary dwellings)

  Confirm yourself

  An attached secondary dwelling triggers fire-separation requirements under the National Construction Code. The specific construction requirements must be confirmed by your certifier or building surveyor — this is a safety-critical item, not a self-serve check.

• BASIX / NatHERS

  Confirm yourself

  A BASIX certificate is required for a new secondary dwelling, setting energy and water targets. The current target values and whether NatHERS modelling is needed for your build must be confirmed.

The four compliance packs

Included in the Granny Flat Toolkit.