Can I Build a Granny Flat? NSW Rules and Eligibility in 2026

If you own a residential block in NSW and have wondered whether you can build a granny flat on it, the answer is usually yes, but the rules have changed several times since the original Affordable Rental Housing State Environmental Planning Policy (SEPP) was introduced. This guide cuts through the noise with the eligibility criteria as of early 2026, what each Western Sydney council expects, and where the policy traps still are.

What counts as a granny flat in NSW

Under NSW planning law a granny flat is a secondary dwelling on a residential lot, ancillary to a principal dwelling. It must be on the same title (not a separate lot), have its own kitchen, bathroom and at least one bedroom, and be no more than 60 square metres of internal habitable floor area. You can also have a covered patio, a small carport and basic landscaping that does not count toward the 60 sqm cap.

If you are thinking of building two separate dwellings on the same land where neither is clearly secondary to the other, that is a dual occupancy or duplex, not a granny flat, and the planning pathway is different.

The minimum eligibility criteria for the CDC pathway

To qualify for the fast-track Complying Development Certificate pathway under the Affordable Rental Housing SEPP, your block must:

• Have a minimum area of 450 square metres.
• Have a minimum frontage of 12 metres at the building line (some councils accept slightly less for irregular blocks).
• Be zoned R1, R2, R3 or R4 (general residential).
• Already have an existing principal dwelling, or be approved to build one at the same time.
• Meet setback rules: typically 3 metres from rear and side boundaries, with some variations for corner lots.
• Have appropriate access for sewer, water and stormwater connection.
• Not be in a flood-prone zone, bushfire-prone area subject to BAL 40 or above, or a heritage conservation area without further checks.

If your block ticks every box, you can typically obtain CDC approval in 8 to 10 weeks through a private certifier, with no need to lodge anything with council.

What if your block does not meet the SEPP criteria

If your block is smaller than 450 sqm, narrower than 12 metres, in a heritage conservation area, or in a high-bushfire zone, you cannot use the CDC pathway, but you may still be able to build a granny flat under your local council’s Local Environmental Plan (LEP) through a full Development Application. DA timelines run 12 to 30 weeks depending on council and complexity. Approval is at council’s discretion and is not guaranteed.

The councils we work with regularly that have more permissive LEP provisions are Blacktown, Liverpool and Penrith. The Hills Shire and Hornsby tend to be stricter, particularly on lot density and tree retention.

Setback rules and where the design constraints bite

The 3 metre rear and side setbacks under the SEPP are the most common reason a design has to be redrawn. On a 15 metre wide block with an existing house in the middle, you often only have 6 metres of width to work with at the rear, which limits the granny flat layout.

Sometimes the answer is to attach the granny flat to the existing house as an attached secondary dwelling, but that has its own rules (it must still have a separate entry and not share rooms with the main dwelling). Where the existing house already takes most of the block depth, an attached granny flat is sometimes the only feasible design.

Council development contribution fees

Each council charges development contributions (formerly Section 94, now Section 7.11 or 7.12) on top of approval fees. For Western Sydney granny flats in 2026, expect:

• Blacktown: roughly $5,500 to $7,500
• The Hills Shire: roughly $7,500 to $11,000
• Penrith: roughly $5,500 to $7,500
• Camden: roughly $6,000 to $8,500
• Liverpool: roughly $4,500 to $7,000
• Cumberland: roughly $4,500 to $6,500
• Parramatta: roughly $7,000 to $10,000
• Hornsby: roughly $6,500 to $9,500

These contribute to local infrastructure (roads, drainage, open space) and are not negotiable. Confirm with your council before signing a build contract.

Common reasons granny flat applications get rejected

1. Block under 450 sqm with no LEP fallback.
2. Inadequate stormwater plan, particularly on flat or low-lying blocks.
3. Tree removal proposal where the council requires retention.
4. Setback breach (very common where designers try to make the granny flat too big).
5. Existing unapproved structures (sheds, decks) on the block that need to be regularised first.

Final thoughts from the engineering side

A granny flat is one of the highest-yield improvements you can make to a Western Sydney property right now. Rental returns of $450 to $650 per week on a $170,000 to $200,000 build deliver 12 to 16 percent gross yield, well above what direct property investment returns. The key is doing it under a clean approval pathway with a builder who knows the council you are dealing with.