You want to push out the back, add a bedroom, lift the roofline. Whether the authorities treat that as a renovation or a from-scratch rebuild — two different approval routes, two different timelines, two very different bills — is decided before you draw a thing. Get the classification right and the rest of the project has a frame to hang on. Get it wrong and you redesign halfway through, after you've already paid for drawings. This guide walks the whole path: the planning test that sets your route, the money metric that sets your budget, the team you must hire, the certificates that close the job, and the things hiding in the ground that decide more than the design ever will.
The short version
A&A or reconstruction — what the test actually is
URA splits landed building work into two plan-lodgment routes. Additions & Alterations (A&A) go in on one track. New Erection or Reconstruction — together the "rebuild" category — go in on the heavier one. Demolish the whole house and you are a New Erection by definition. Keep part of it but go too far, and you cross from A&A into Reconstruction.
To stay an A&A, a proposal has to satisfy all five of the following conditions. These come from URA's Development Control Guidelines for Additions and Alterations to Landed Housing:
On top of those three 50% limits and two roof/attic conditions sit two absolute bars. Cross either and the works become a Reconstruction regardless of any percentage:
