How Long Does a Granny Flat Take, From Enquiry to Keys?

Last reviewed: August 2026

On the fast approval pathway, a Sydney granny flat typically runs about six to nine months from first enquiry to handover. Roughly two months of that is design and documentation, one to two months is approval, and three to four months is construction. On the council approval pathway, add three to six months.

The part people underestimate is not construction. It is everything that has to happen before construction can start.

The full timeline

Stage	Typical duration	What is happening
Site assessment and quote	1 to 2 weeks	Inspection, measure up, fixed price quote
Design and selections	2 to 4 weeks	Plan chosen or customised, finishes selected
Survey, soil test, engineering	2 to 4 weeks	The reports every approval needs
BASIX and documentation	1 to 2 weeks	Energy assessment, final drawings
Approval, CDC	4 to 6 weeks	Certifier assesses against the standards
Approval, DA	3 to 6 months	Council merit assessment, often with neighbour notification
Construction	12 to 16 weeks	Slab through to handover
Final certification and handover	1 to 2 weeks	Occupation certificate, keys

BlueGum’s published figures are 4 to 6 weeks for CDC approval and 12 to 16 weeks for construction.

Add it up on the fast pathway and you get roughly six to nine months. On the council pathway, roughly nine months to a year.

Where the time actually goes

Before approval: the part nobody counts

You cannot lodge an approval application until the survey, soil test, engineering drawings and BASIX certificate are done. Those are separate professionals with their own schedules.

This stage is where most of the avoidable delay lives. It is also almost entirely front-loaded, which means the sooner it starts, the sooner everything else can follow.

Approval

On the complying development pathway, a certifier is checking your plans against a fixed list. There is no discretion, so once the documents are complete and compliant, it moves.

You will see this quoted as 10 to 20 business days. That figure comes from certifier practice rather than legislation, and it assumes a complete application. If something is missing, the clock effectively restarts when you supply it.

On the development application pathway, council is assessing on merit. That involves notification periods, internal referrals, and often requests for further information. Three to six months is normal, and it can run longer on a complex site.

Construction

Twelve to sixteen weeks is a realistic range for a straightforward granny flat.

Construction stage	Typical duration
Site set-up, excavation, services	1 to 2 weeks
Slab	1 to 2 weeks
Frame and roof	2 to 3 weeks
Lock-up: windows, doors, external cladding	2 weeks
Rough-in: electrical, plumbing	1 to 2 weeks
Internal linings and fit-out	3 to 4 weeks
Finishes, painting, external works	2 to 3 weeks
Final inspections and handover	1 to 2 weeks

What causes delays

Cause	Effect	Can you prevent it
Incomplete approval documents	Approval clock restarts	Yes, with an organised builder
Rock found during excavation	Days to weeks, plus cost	Partly, with an early soil test
Wet weather	Days to weeks, mostly at slab stage	No
Changing your mind on finishes	Days to weeks	Yes, lock selections early
Variations after start	Days to weeks each	Yes, get the scope right up front
Sewer diversion needed	Weeks to months	Yes, check the service diagram early
Council requests further information	Weeks	Partly, with complete lodgement
Trade or material availability	Days to weeks	No, but a builder with steady trades helps

The pattern is worth noticing. Most of the preventable delays happen before a single trade turns up, and most of them come down to how thoroughly the early work was done.

How to make it go faster

1. Get the site assessment done early. Everything else depends on knowing what the block is like.
2. Order the soil test and survey as soon as you commit. They sit on the critical path.
3. Lock your finishes selections before construction starts. Changing a benchtop after the kitchen is ordered costs weeks.
4. Use one party for approval and construction if you can. Splitting them adds a handover point where things wait.
5. Answer questions quickly. Approval and construction both stall on decisions.

Frequently asked questions

Can a granny flat be built in three months?

Construction alone can be twelve to sixteen weeks, so roughly three to four months. But that is measured from slab to handover, not from your first phone call. Design, documentation and approval come first, and they typically add three to five months on the fast pathway.

What is the longest part of the process?

On the complying development pathway it is construction. On the development application pathway it is council approval, which can take three to six months on its own.

Does winter slow it down?

Wet weather affects the early stages most, particularly excavation and the slab pour, because those need reasonably dry conditions. Once the roof is on, weather matters much less.

Can I live in the main house during construction?

Yes, in almost all cases. There will be noise, trades and machinery, and access to part of your yard will be restricted, but the main house stays liveable.

What happens at handover?

Final inspections are completed, an occupation certificate is issued, and you get the keys. Ask your builder what warranty period applies and how defects are handled after handover, because that varies.

Get a timeline for your block

Every timeline on this page assumes a straightforward site. Slope, rock, heritage or flooding change it, and the only way to know is to look.

Check your block, or call BlueGum on 1300 060 651 to book a site assessment.

BlueGum Granny Flats is a licensed NSW builder, licence number 247388C. Timeframes are indicative and depend on the site, the approval pathway, and factors outside any builder’s control including weather and authority processing times.