A granny flat goes through the same broad stages whether it is a kit design or drawn by an architect. Knowing the order of those stages, and where projects usually stall, makes it easier to plan your budget and your builder's start date. Sites vary too much for us to quote a standard number of weeks, but we can show what happens when.
Stage 1: find out what the site allows
Gather the information that limits the design before anyone starts drawing:
- a section 10.7 planning certificate, which shows zoning and any bush fire, flood or heritage constraints
- a survey plan showing levels, boundaries, easements and existing structures
- the location of sewer and stormwater pipes, including any main crossing the back yard
- significant trees that may need council approval before removal
This is where most surprises are found. An easement or a sewer main can move the whole building, so it pays to know early. Lot size matters too: our guide to Granny flat rules in NSW: size, lot and setback basics explains the 450 m² threshold.
Stage 2: design and supporting documents
An application usually needs architectural plans, a BASIX certificate, structural engineering for the slab and frame, and a stormwater design. A bush fire assessment is needed on bush fire prone land, and a geotechnical report on some sites. Each consultant works to their own schedule, and every change to the plans can send reports back for updating. Settle the design first, then order the reports.
Stage 3: approval
Where the design satisfies the complying development standards, the certifier assesses it for a CDC. For metropolitan sites, neighbours within a 20 metre radius get written notice, and approval has to wait 14 days after that. Where council approval is required instead, council assesses the DA. A construction certificate then follows the consent.
Requests for information (RFIs) are the most common cause of delay at this stage. They usually come from missing details or drawings that don't agree with each other. A thorough set of plans, and quick answers when questions do come, keep things moving.
Stage 4: building and inspections
Before work begins, you appoint a principal certifier, lodge a notice of commencement and give nearby neighbours notice (a week or more ahead in metropolitan areas). During construction, the principal certifier inspects the work at set critical stages, explained in our guide to Critical stage inspections: what we check and when.
Ask your builder to book each inspection at least 48 hours ahead and to have the site ready. A failed inspection means rework and a second visit, and the next trade often can't start until it passes.
Stage 5: the occupation certificate
Nobody can move in until an occupation certificate (OC) is issued. That needs a final inspection plus paperwork from the trades, such as waterproofing, electrical and plumbing certificates and evidence that the BASIX commitments were met. Our Occupation certificates: what you need before moving in lists the usual documents. Ask for each certificate as soon as that trade wraps up, rather than hunting for paperwork once the build is over.
What pushes time and cost up
- Site constraints found late, such as an easement, a sewer main or bush fire mapping.
- Design changes after approval, which may need a modified certificate before building continues.
- Slow RFI replies, and documents that contradict each other.
- Failed inspections, which cost a return visit and stall the next trade.
- Missing trade certificates at the end, which hold up the OC.
CertifiBuild certifies granny flats from plan check to OC. See our granny flats page or request a quote for your project.
Local help across NSW
CertifiBuild certifies Class 1 and Class 10 work in 39 council areas. Local rules on these council pages are a good place to start: Blue Mountains City Council, Sutherland Shire Council, Wollondilly Shire Council, Lithgow City Council, Shellharbour City Council, City of Ryde.
Suburb pages with local planning notes: Sans Souci, Springwood, Taren Point, The Oaks, Wallerawang, Warilla, West Ryde, Willoughby, Wongawilli, Woolooware. You can also browse every service area.
Sources
- Telling neighbours about complying development, NSW Planning Portal
- Secondary dwellings guidance, NSW Department of Planning
- State Environmental Planning Policy (Housing) 2021, NSW Legislation