do i need council approval for a deck

There is no national rule, and this is the question where general advice does the most damage, because the numbers genuinely differ. What is consistent is the shape of the test: exemptions turn on how high the deck is above natural ground, how large it is, whether it is attached to the dwelling, and how close it sits to a boundary.

What usually pushes a deck into needing approval

• Height above ground, because once people can fall from it, balustrade requirements and structural loads apply.
• Attachment to the house, which makes it part of the building rather than a separate structure.
• A roof over it, which changes it from a deck to a roofed structure and often triggers planning as well as building approval.
• Proximity to a boundary, which brings in fire separation and overlooking considerations.
• Overlays on the land: heritage, bushfire, flood, or a covenant on the title.

Two approvals, not one

Building approval is about whether the structure is sound and complies with the construction code. Planning approval is about whether the land use and appearance are acceptable in that location. A deck can be exempt from one and require the other, which is the most common misunderstanding in this whole area.