Shea CullenNSW Registered Architect 9748 · Updated 6 July 2026A granny flat, or secondary dwelling, is the fastest way to add a second income or house family on a block you already own, and much of it can go through the quicker complying development pathway rather than a full development application.
Two numbers decide most projects. You generally need a lot of at least 450m², and the secondary dwelling can be up to the greater of 60m² or 30% of your main house's floor area under Central Coast LEP clause 5.4(9), so on a larger home you are not stuck at 60m². The catches are the site constraints, flooding, bushfire, easements and setbacks, which is where the checklist below starts.
If you are prone to flooding you will need to get a flood information certificate. If you are bushfire prone, you will need to get a bushfire report.
Highly recommended. Use the Central Coast Council predevelopment meetings form to book a free callback to discuss your site.
The Housing SEPP sets 60m² as the maximum gross floor area for a secondary dwelling, **or larger where another planning instrument allows it**, and on the Central Coast one does. Central Coast LEP 2022 clause 5.4(9) permits the greater of 60m² or 30% of the principal dwelling's floor area, excluding parking. So on a lot with a 300m² house you can go to 90m², not 60m². This is the single most under-used control in Central Coast granny flat design, because almost every online guide quotes the state 60m² figure and stops there. Work out 30% of your existing house before you settle on a plan.
Conditions apply if the site is bushfire or flood affected, or if it is near a heritage item. Check this with the Central Coast Council Online Mapping by turning the layers on and off.
Lot setback and landscaping requirements vary by lot size: 450 to 600m², 600 to 900m², 900 to 1500m², and over 1500m² each have different maximum GFA, minimum landscaping, frontage, height and setback rules. Check the table for your lot size.
Engage a quality surveyor to produce a site plan with boundaries, levels and existing services.
Engage an architect to provide both plans and specifications for a well oriented, beautifully designed granny flat.
Submit on the NSW Planning Portal. The submission fee is around $25 at time of writing.
Engage a structural engineer, typically around $2,500.
Can be obtained from Central Coast Council through their Online Services Portal, or through infocert.
You will need either qualified builder details or to become an Owner Builder. Note this is different to a carpenter. It must be a qualified builder.
Either Central Coast Council or a private certifier. Central Coast Council fees are around $2,345 at time of writing.