Granny Flat Rules in NSW 2026: Blacktown, The Hills and Penrith Compared

A granny flat — the official NSW term is a secondary dwelling — remains one of the strongest yield plays in Western Sydney real estate. Rent a 60 m² two-bedroom cottage in Blacktown for $450 to $520 a week; put the same build in Castle Hill and it clears $580 to $680. On a 600 m² block that already has a house, the secondary dwelling is the highest and best use of the back yard nine times out of ten.

What has changed for 2026 is not so much the state rules — the State Environmental Planning Policy (Housing) 2021 (which subsumed the older Affordable Rental Housing SEPP) still sets the floor — but how each council’s DCP layers on top. Here is how Blacktown, The Hills Shire and Penrith City actually treat granny flats in 2026, and where they diverge.

The NSW state rules in one paragraph

Under the Housing SEPP (chapter 3, division 4) a secondary dwelling can be approved as complying development if the primary lot is at least 450 m² in area, the secondary dwelling is no more than 60 m² of gross floor area, the total site coverage stays under the zone’s control, and the secondary dwelling shares the same lot as the principal dwelling. Setbacks, height and separation come from the code. Approval is by a private certifier as a CDC; typical issue time is 6 to 12 weeks.

On blocks below 450 m², or where the design cannot meet the CDC setbacks, the secondary dwelling goes to DA under the relevant council’s LEP and DCP. That is where the three councils diverge.

Blacktown City — the friendliest of the three

Blacktown treats secondary dwellings as a permitted use in R2 Low Density and R3 Medium Density zones under Blacktown LEP 2015. Blacktown DCP 2015 Part J covers the design detail. A few Blacktown-specific points worth knowing in 2026:

• Blacktown does not require a separate access driveway. A shared driveway to the primary house is acceptable.
• Council allows 60 m² gross floor area under the state code. Under a DA, Blacktown can approve slightly more where site constraints justify it — we have had 66 m² approved on wider blocks in Marsden Park.
• Rear setbacks of 3 m are the DCP norm; side setbacks match the primary dwelling’s.
• Blacktown’s flood mapping around Eastern Creek excludes some blocks from CDC. On those blocks the granny flat goes DA and floor levels must sit at the flood planning level.

Typical Blacktown granny flat cost in 2026: $149,000 to $189,000 for a two-bedroom, fully finished with council fees included. Rents are in the $450-$520 range for the west (Blacktown, Mount Druitt, Seven Hills) and $500-$570 for the north-west of the LGA (Kings Langley, The Ponds).

The Hills Shire — bigger blocks, stricter design controls

The Hills Shire assesses secondary dwellings under The Hills LEP 2019 and The Hills DCP 2012 Part B chapter 4. It is the strictest of the three:

• The Hills often requires a minimum lot size of 500 m² in practice, even where the state code allows 450 m². Council can refuse a CDC referral if the DCP standard is not met.
• Tree protection is genuine. Any tree over 3 m tall or 30 cm girth at 1 m needs an arborist report and a tree protection plan, and often has to stay.
• The DCP encourages the secondary dwelling to be visually subordinate to the main house — matching roof pitch, matching materials, no independent driveway.
• Site coverage under the R2 zone in The Hills is 40% (versus 50% in Blacktown R2), which limits what fits on smaller lots in Castle Hill or Kellyville.

Typical cost in Kellyville, Castle Hill, Bella Vista and Rouse Hill in 2026: $169,000 to $215,000. Rents: $580-$680 for a two-bedroom. The higher rent generally covers the higher build cost, but the approval path is more work.

Penrith City — the middle ground

Penrith sits between the two on both approval friendliness and market rent. Assessed under Penrith LEP 2010 and the Penrith DCP 2014 (updated 2025), Penrith’s secondary dwelling treatment is close to Blacktown’s for CDC, and moderately more prescriptive for DA:

• Penrith allows the state code’s 60 m² threshold and 450 m² primary lot minimum without adding on top.
• The DCP requires a private outdoor open space of 24 m² per dwelling. On a small block this can be the constraint.
• Penrith’s flood mapping (Nepean, South Creek and their tributaries) excludes some blocks from CDC — St Marys, Cambridge Park and parts of Werrington are the common flags.
• Off-street parking: one space per dwelling. A tandem arrangement counts, which is helpful on narrower lots.

Cost in Penrith and its suburbs (St Marys, Werrington, Kingswood, Jordan Springs) in 2026: $145,000 to $185,000. Rents: $420-$500 depending on suburb and finish level.

Head-to-head comparison

When a granny flat doesn’t stack up

The maths falls over in three situations. First, on a block below 450 m² — the CDC pathway shuts and a DA is uncertain. Second, when the primary house occupies more than half the yard — you cannot get 60 m² plus outdoor space in the remainder. Third, when the block is flood affected above the CDC threshold — the extra site works (elevated floor levels, flood-compatible construction) push the cost past what the rent supports.

In those cases we usually recommend either a second storey addition (see our knockdown rebuild guide for when tear-down beats extension) or a full duplex build if the block and zoning allow.

Frequently asked questions

Can I rent out a granny flat in Blacktown or does council restrict it?
Yes — the whole point of the secondary dwelling framework is to allow rental. There is no council-level restriction on renting to a non-family member in Blacktown, The Hills or Penrith. The state Residential Tenancies Act applies as normal.

Do I need council approval to build a granny flat in The Hills Shire?
Yes. Either a CDC issued by a private certifier under the Housing SEPP, or a DA to The Hills Shire Council. There is no exempt-development pathway for a habitable secondary dwelling.

How long does a granny flat CDC take in Penrith?
Typical CDC issue time in Penrith is 6 to 10 weeks with a private certifier, assuming the file is complete. Construction after CDC issue is 14 to 18 weeks. Whole project from signed contract to handover is roughly 6 to 8 months.

What is the minimum block size for a granny flat in NSW in 2026?
450 m² under the state Housing SEPP for CDC. Below that, you need a DA and the outcome is uncertain — depends heavily on how the block sits, how the primary dwelling is placed, and what the council’s DCP allows.

Can I use a granny flat as an Airbnb in Western Sydney?
Short-term letting is regulated at state level in NSW (register on the STRA register, 180-day cap per year if non-hosted). Council DCPs don’t override that but can add planning tests. In Blacktown and Penrith it is common; in The Hills the DCP is stricter and some streets have specific STRA controls.

Does a granny flat need its own electricity meter?
Not required by council. Most owners install a separate sub-meter so the tenant’s usage is measured, and either bill through or hand billing to the tenant. A separate primary meter is more expensive and only worth it for long-term or granny flats intended for eventual title split (which is a whole other approval).

Planning a granny flat in Blacktown, Kellyville, Penrith or anywhere in Western Sydney? Get a fast fixed-fee quote — we handle the CDC, construction and handover as one contract.