Secondary dwelling / granny flat (NSW)
Granny flat (secondary dwelling) in NSW: Housing SEPP 2021 allows them in R1-R5 zones on 450 m²+ lots, 60 m² max floor area, CDC fast-track available.
Ask Chalkline about this →A granny flat is the everyday name for what NSW planning law calls a secondary dwelling: a self-contained second residence on a lot that already has (or is proposed to have) a principal dwelling. It has its own kitchen, bathroom, and entry, and is occupied independently of the principal house. The two terms refer to the same thing; “secondary dwelling” is the formal planning name in NSW legislation, “granny flat” is the term clients and builders use day-to-day.
A secondary dwelling is not the same as a dual occupancy. Two distinguishing features:
- Principal-plus-secondary versus equal-and-equal. A secondary dwelling sits below a principal dwelling in size and status. A dual occupancy is two equivalent dwellings.
- Subdivision. A secondary-dwelling lot cannot be subdivided: the two units stay on one title. A dual-occupancy lot can be subdivided (subject to minimum lot rules).
NSW state-wide rules under the Housing SEPP 2021. The SEPP overrides any LEP that previously prohibited secondary dwellings. Standards:
- Permitted in zones: R1, R2, R3, R4, R5.
- Floor area cap: 60 m² internal floor area for the secondary dwelling (excludes deck, carport, patio).
- Minimum lot size for CDC pathway: 450 m². Lots below 450 m² can still go via DA through council, but cannot use the CDC fast-track.
- One per lot: a single secondary dwelling, regardless of lot size.
- Form: attached to the principal dwelling, integrated within it, or detached as a free-standing structure.
Two approval pathways.
- CDC (Complying Development Certificate), the fast-track. Issued by a private certifier under the Codes SEPP (Exempt and Complying Development Codes 2008). Typical determination is 10 to 20 business days for compliant lots. Requires 450 m² minimum and meeting all the Schedule 1 development standards.
- DA (Development Application) through council, where the CDC pathway is unavailable (smaller lot, contamination, heritage, flooding, bushfire BAL above the CDC threshold, etc.).
Other states. VIC: “dependent person’s unit” or “small second dwelling” under Plan Melbourne and council schemes. QLD: “secondary dwelling” or “auxiliary unit” under most council planning schemes. The NSW model (state-wide permission across all residential zones, capped at 60 m², no subdivision) is the most permissive of the three.
For builders. Granny flats / secondary dwellings are a high-volume product category. The CDC fast-track makes them attractive provided the lot meets the 450 m² rule and clears the Codes SEPP exclusions (no heritage, no bushfire BAL above the threshold, no contamination). On lots that fail CDC, the DA route still works but the timeline doubles or triples.
Granny flat builds at a glance:
| Item | Typical 2026 NSW range |
|---|---|
| Build cost (60 m² turnkey) | $130,000 to $250,000 ex-GST |
| Time on site | 14 to 22 weeks |
| CDC approval lead time | 10 to 20 business days |
| DA approval lead time | 60 to 120 days |
| Rental yield (typical) | $300 to $650/week metro Sydney |
Also known as: granny flat (the everyday name), second dwelling, ancillary dwelling.
Category: Approvals / planning / housing / NSW.
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Last updated: 2026-05-14. Verified: 2026-05-14.