By Phil Brown · Published 14 April 2026
Quick answer: In NSW you can generally build one secondary dwelling (granny flat) of up to 60 square metres of living space on a residential block of at least 450 square metres. Where your site meets the complying development standards, a private certifier can approve it in as little as 1 to 2 weeks, no DA required. Flood, bushfire and foreshore overlays can change the pathway, which is why the site check comes first.
The NSW housing policy allows a secondary dwelling on most residential-zoned lots of 450 square metres or more. The granny flat itself can have up to 60 square metres of living area, must share the lot with the main home (you cannot subdivide it off), and only one secondary dwelling is allowed per property. It can be attached, detached, or a conversion of existing space like a garage. Setbacks, height and landscaping rules still apply, and they tighten on smaller lots.
Most granny flats that comply with the standards can be approved as complying development, which means a private certifier signs off instead of council, typically within weeks. Our guide to DA vs CDC explains the difference in detail. On the Northern Beaches, flatter unconstrained blocks in suburbs like Cromer and Wheeler Heights are ideal CDC territory.
Overlays. Flood-affected land near Narrabeen Lagoon, bushfire-prone land in suburbs like Bilgola and Ingleside, and foreshore controls around Pittwater can each push a granny flat from CDC into DA territory, or shape where on the block it can sit. None of these usually stop the project; they change the paperwork and sometimes the construction spec.
A well-designed granny flat adds a rental income stream, houses family affordably, and lifts the property's value. Design quality is the multiplier: orientation, privacy from the main house and a layout that works for real tenants separate the granny flats that rent instantly from the ones that don't. See our granny flat design service for how we approach it, including our recent secondary dwelling in Palm Beach.
FAQs
Yes. NSW allows secondary dwellings to be rented separately from the main home, which is exactly why they're popular as investments on the Northern Beaches.
Under the complying development standards a secondary dwelling generally doesn't trigger an additional parking requirement, though site specifics matter. We confirm this during the free eligibility check.
Design from around $4,000, approval drawings from $2,500 and construction documentation from $1,500, with a fixed quote after a free site assessment. Build costs are separate and depend on size and spec.
Phil Brown is a Northern Beaches born and bred draftsman and building designer. Since 2016, Northern Beaches Drafting has prepared DA and CDC plans from Manly to Palm Beach and across the Central Coast. Get a free fixed-price quote or call 0414 978 499.
Free, no-obligation fixed-price quotes for drafting, DA and CDC plans across the Northern Beaches.