Box Hill’s newer residential estates include many smaller blocks, so whether you can build a granny flat depends closely on the size, layout and planning controls of your individual property. Lots of around 300–450m² are common, and under the NSW Housing SEPP, a secondary dwelling on a lot below 450m² cannot use the complying development pathway, although a Development Application (DA) may still be possible. On lots of at least 450m², a granny flat may qualify for complying development if all other requirements are met, including the applicable 60m² floor area limit. As part of The Hills Shire Council area, Box Hill also has local site considerations such as flooding within the Killarney Chain-of-Ponds catchment. A property assessment is the best way to confirm what can work on your block before choosing a design.
Get inspiration from our recent granny flat projects across Box Hill and surrounds — and see how we’ve turned different properties into practical new spaces.
Box Hill is one of The Hills Shire’s rapidly growing residential areas, with thousands of additional homes planned as the community continues to expand. For homeowners, a granny flat can make an existing property more useful without moving to a larger block, particularly where newer homes are built on more compact lots. It can provide private accommodation for ageing parents, adult children or extended family, while also giving homeowners the option of using the space as a rental property when circumstances change. With more people moving into the area and continued housing growth planned, a well-designed granny flat can also provide greater flexibility for the future. In Box Hill, where available space needs to be used carefully, the right layout can create a practical second dwelling while maintaining a comfortable connection to the main home.
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The three things that shape a granny flat build in Box Hill: the planning rules, the ground you’re building on, and what the market gives back.
Median house price in Box Hill
Typical granny flat rent
Key local landmark
your block
nearest station
A granny flat in Box Hill can be approved through a private certifier as complying development when the lot is 450m2 or larger, the secondary dwelling is no more than 60m2 (or 25% of the main house, whichever is less), and setbacks, height and landscaping meet Housing SEPP 2021 standards. This pathway typically takes 10 to 15 business days once documentation is complete. Blocks inside a flood planning area can still qualify, but floor levels and fill must meet the council's flood controls, which we check against the flood certificate before design. With many lots in Box Hill under 450m2, we measure the lot from the title before assuming this route is open.
Not meeting one complying development requirement does not rule a project out. Where a block in Box Hill is under 450m2, sits in a heritage conservation area, or is affected by a flood planning control, a development application can be lodged with The Hills Shire Council. Assessment times are longer than a CDC, but the council does approve secondary dwellings through this route.
Box Hill is administered by The Hills Shire Council and assessed under the Hills LEP 2019. The whole suburb falls within the one council area. Granny Flats X confirms the consent authority for your specific block during the initial property assessment.
Get a free site assessment and fixed-price estimate for your Box Hill project.
The things Box Hill homeowners ask us most. Can’t find yours? Call us — we’ll give you a straight answer.
Usually 12-14 weeks from approval. We fast-track the council paperwork.
Yes. Most Box Hill blocks support 60m² 2-bedroom layouts.
Yes, but we handle the entire approval process for you.
