Suitability comes first
NSW Planning notes that complying development can depend on requirements such as lot size and floor area. The actual block needs review before eligibility is assumed.
Design still matters
A compact dwelling still needs privacy, light, services, access and a finish level that suits the main property.
Do not rely on generic advice
Planning controls, existing approvals, bushfire, flood, heritage and local requirements can change the pathway. Use the early conversation to review the real block, not a general assumption.