State Environmental Planning Policy (Housing) 2021

Development for the purposes of a secondary dwelling or an ancillary structure must not result in a new building or a new part of an existing building or a new carport, garage, balcony, deck, patio, pergola, terrace or verandah having a setback from a side boundary of less than the following—

for a lot with an area of at least 450m² but not more than 900m²—0.9m,

for a lot with an area of more than 900m² but not more than 1,500m²—1.5m,

for a lot with an area of more than 1,500m²—2.5m.

Development for the purposes of a secondary dwelling or an ancillary structure must not result in a new building or ancillary structure having a setback from a side boundary of less than the sum of—

the amount of the setback specified for the relevant sized lot in subsection (1), and

an amount equal to 25% of the additional building height above 3.8m.

In this section—

a new building or a new part of an existing building with a height of more than 3.8m, and

a new carport, garage, balcony, deck, patio, pergola, terrace or verandah.