An outbuilding may be considered exempt development if it meets the criteria of the State Environmental Planning Policy (Exempt and Complying Development Codes) 2008.
2.18 sets standards such as zone, height, setback, floor area, materials, and the like.
For related information such as zoning requirements. Please refer to the NSW Planning Portal and use the Spatial Viewer to search for a property.
If your development doesn’t meet exempt it will require a DA, which can be lodged through the NSW Planning Portal. Further guidance for these controls can also be seen in the relevant Development Control Plan.