1. Decide how the space will be used
Start with the people and purpose, not a floor plan. A self-contained home for long-term occupation is different from a backyard office, guest room, workshop or storage building. The intended use affects the building classification, required facilities, energy and accessibility decisions, approvals and budget.
Write down the likely occupants, required bedrooms, kitchen and bathroom needs, privacy, step-free access, storage, working-from-home needs and whether rental use is contemplated. If needs may change, identify the decisions that are difficult to alter later: door widths, bathroom layout, services, structure and site access.
2. Screen the property before paying for a design
Sketch the existing home, boundaries, driveway, trees, sheds and the possible building area. Then locate title restrictions, easements, sewer and stormwater infrastructure, slope, flood or bushfire constraints, access for construction equipment and the distance to services. A survey and professional advice may be needed before these assumptions are reliable.
- Can materials and machinery reach the proposed building area?
- Are easements, large trees or services inside the apparent footprint?
- Will the new building affect private open space, overlooking, daylight or drainage?
- Is the existing dwelling lawful, and are there unresolved permits or additions?
3. Identify the correct planning term and approval pathway
“Granny flat” is a common search term, not one national legal definition. Victoria commonly uses small second home or small second dwelling; New South Wales uses secondary dwelling; Queensland also uses secondary dwelling; other jurisdictions use terms such as ancillary dwelling, ancillary accommodation or secondary residence.
In Victoria, a small second home is generally a self-contained dwelling of 60 m² or less on the same lot as an existing home. A building permit is always required, while a planning permit is not required in many cases; zones, overlays, lot size and other controls can change that. In NSW, secondary dwellings may use complying development or a development application depending on the site and compliance with the relevant standards.
4. Build an all-in project budget
A base building price is not the same as the completed project cost. Allow for concept design, survey, soil testing, engineering, energy assessment, planning advice, permits or certificates, demolition, excavation, foundations, cranage, service connections, drainage, driveways, decks, landscaping, professional fees, finance and contingency.
Use the same scope when comparing prices. Ask providers to identify exclusions and provisional allowances in writing. Our granny flat cost guide explains the largest variables and gives an indicative starting range.
5. Turn the research into a site-specific brief
A useful brief combines the intended use with site evidence. Include a survey or accurate site information, rooms and approximate sizes, accessibility needs, orientation, privacy, material preferences, energy goals, budget range and must-have completion date. State which decisions are fixed and which are open to professional advice.
For a cabin, studio, modular building or prefabricated granny flat, also ask what work occurs off-site, what must be completed on-site, how the building will be transported, who designs the footing system and whether access has been checked.
6. Assemble the right team and compare proposals
Depending on the project, you may need a registered builder, building designer or architect, town planner, land surveyor, structural engineer, energy assessor, building surveyor or certifier, plumber, electrician and other trades. Some design-and-build companies coordinate most of this team; others supply only a shell or kit.
For every proposal, confirm business identity, registration or licence where applicable, insurance, relevant completed projects, references, contract type, payment schedule, inclusions, exclusions, allowances, variation process, approval responsibility and defects process. Compare the same scope rather than choosing the lowest headline figure.
7. Secure approvals before authorised work begins
Do not rely on phrases such as “permit-free” without checking what permit, building type, use and jurisdiction the claim refers to. Obtain the required planning approval, building permit, complying development certificate or construction certificate for the actual site and design. Confirm who will arrange mandatory inspections and what documents must be available on site.
8. Document handover and ongoing responsibilities
Before final payment, inspect the work against the plans, specifications and contract. Record defects, collect certificates, approvals, warranties, manuals, product information, keys and final drawings, and understand maintenance requirements. Confirm that occupation is lawful before anyone moves in or the dwelling is advertised for rent.
Your next three actions
- Find the property’s council, zone and obvious constraints using the council research guide.
- Create an all-in budget range, including a contingency.
- Compare professionals only after you can send each one the same useful brief.
This guide is general information, not planning, legal, financial, building or construction advice. Requirements change and depend on the property and proposal. Verify current requirements with the relevant authority and appropriately qualified professionals.