Owner-builder work is essentially any work (in addition to organising and supervising) involving the construction of, or alterations, repairs or additions to a dwelling:

Where the reasonable market cost (inclusive of materials and labour) exceeds $20,000 and is in relation to a single dwelling-house or a secondary dwelling (possibly in special cases an owner-builder permit may be granted for dual occupancy).

When there is a need for development approval within Part 4 of the Environmental Planning and Assessment Act 1979., or a complying development within Part 4 of the Environmental Planning and Assessment Act 1979.