The question is not surprising considering the plethora of legislation which, if you manage to comprehend, happens to change from Council to Council, and from suburb to suburb, even from house to house. So, just because your neighbour did some work, don’t presume you can do the same.
Firstly, you need to understand your own property. Is it heritage listed or in a conservation area? Is it a draft heritage item? Is it on bushfire prone land or in a foreshore area? Any of these conditions will most likely mean your development, however small, requires a DA. You can find out what restrictions a property has by obtaining a 149(a) or 194(e) certificate from your local Council.
The State Environmental Planning Policy (Exempt and Complying Development Codes) 2008 (referred to in this blog as “the code”) is a piece of legislation with state-wide application describing when development is Exempt, meaning it needs no approval, or Complying, meaning a Complying Development Certificate is required. In both cases a DA is usually not required. However, if the property is heritage listed, has a draft heritage listing, in a foreshore area, or has another limitation as prescribed by the code, then a DA will probably still be required.