Questions to Ask a Granny Flat Builder: Australian Quote Checklist

The short answer

Ask a granny flat builder to price the same defined project as every other builder. The quote should identify the legal contracting entity, proposed approval pathway, plans and specifications, site assumptions, exclusions, payment stages, handover documents and who is responsible for every task between design and a usable second dwelling.

The most important question is not “How much is the granny flat?” It is “What will this property owner still need to arrange and pay for before the dwelling can be lawfully used?”

Use the checklist below before paying a preliminary fee or deposit. It is designed for Australian secondary-dwelling projects, including site-built, modular, panelised and complete prefab options. State contract and approval rules differ, so verify the exact proposal with the relevant council, building regulator and qualified advisers.

If you are still comparing the broader category, start with the Australian granny-flat guide and granny-flat cost breakdown. For a factory-built option, also use the prefab granny-flat buyer guide.

Send every builder the same property brief

A builder cannot produce a useful project quote from a floor plan and suburb alone. Prepare one short brief and send the same information to each shortlisted company:

• property address and council area
• current title, survey or reliable site plan if available
• location of the existing principal dwelling and other structures
• intended use: family accommodation, long-term rental, accessible living or another purpose
• preferred bedrooms, bathrooms, floor area and accessibility requirements
• known easements, sewer lines, trees, slope, flood or bushfire constraints
• available side access and likely crane or construction access
• existing water, sewer or onsite wastewater, stormwater and electrical services
• target complete-project budget, not only the dwelling budget
• preferred timing and any hard deadlines

Do not hide a difficult access point or site constraint to obtain a lower initial number. The quote will become less reliable, not more affordable.

18 questions to ask a granny flat builder

1. What exactly are you quoting?

Ask whether the proposal is a site-built secondary dwelling, a completed module, a panel or kit package, a supply-and-install contract, or several contracts with different businesses. Record the contracting entity for design, manufacturing, site work and installation.

A product described as a “granny flat” is not necessarily a complete secondary-dwelling project. It may be a cabin or module that still needs site-specific design, approvals, footings, connections and a licensed site contractor.

2. Have you reviewed this property before recommending a design?

Ask what title, survey, planning, services and access information the builder has actually checked. A standard design fitting within the backyard dimensions does not show that setbacks, easements, private open space, drainage, fire separation, access or service routes work.

The builder should clearly separate an early sales review from advice supplied by a planner, designer, engineer, building surveyor or certifier.

3. Which approval pathway are you assuming?

Request the exact state and local term the proposal is intended to meet: secondary dwelling, small second home, ancillary dwelling or another defined use. Ask whether the quote assumes a planning permit, development application, complying pathway, building permit or other approval.

In NSW, a secondary dwelling may use development consent or complying development where the project meets the relevant requirements. In Victoria, a qualifying small second home is 60 square metres or less and still requires a building permit, while a planning permit can be needed in some situations. Queensland owners still need to check local development and building requirements. None of these pathways is confirmed by a builder's model name.

4. Who prepares, lodges and answers questions about approvals?

Ask who is responsible for:

• the site plan, architectural drawings and specifications
• planning advice or a planning application
• structural, footing and site engineering
• energy-efficiency and climate documentation
• bushfire, flood, acoustic or other specialist reports
• building approval, inspections and completion or occupancy documents
• responding if an authority requests changes

“Approval support” is too vague. Put a business or adviser beside every task and identify the fee.

5. Which builder licence or registration applies?

Check that the licence or registration is current, covers the proposed work and belongs to the same legal entity named on the contract. If the unit is manufactured by one company and installed by another, ask which entity accepts responsibility for each part.

Do not rely on a salesperson's licence number or a logo belonging to a related company. Use the official state register and keep a copy of the result with the quote.

6. Does the price include site investigation and footing design?

Ask whether the price includes a survey, soil information, engineering and a site-specific footing or slab design. Find out what happens if the soil, slope, existing fill, drainage or access differs from the early assumption.

A low allowance can simply move risk to a later variation. Request the assumed site classification, footing system and quantity behind the price.

7. What is included outside the walls of the dwelling?

Ask the builder to mark every item as included, excluded or not yet known:

Use the site-preparation checklist to identify work that is often absent from a display-price comparison.

8. What does “turnkey” mean in this quote?

Ask for a written definition. “Turnkey” may mean factory-complete, delivered to the property, installed on prepared foundations, connected to services, or genuinely ready for lawful occupation. Those are different handover points.

The specification should identify the exact fixtures, appliances, finishes, heating and cooling, window coverings, floor coverings, external works and connection work. If a selection has only an allowance, record the quantity, quality level and adjustment method.

9. How will the home reach and move around the site?

For modular or prefab proposals, request a preliminary delivery and placement plan. Confirm module dimensions and mass, truck access, turning space, overhead clearance, crane position, ground bearing requirements, traffic control and responsibility for permits or escorts.

For site-built work, ask how trades, materials, waste and machinery will reach the backyard without damaging the main house, driveway, fencing or neighbouring property. Read the delivery and installation guide before accepting a simple “delivery included” line.

10. What assumptions could change the price?

Ask for every provisional sum, prime cost, allowance, estimate and owner-supplied item. The builder should explain what was assumed, when the real cost becomes known, whether labour, freight, GST and margin are included, and how a saving or overrun is handled.

Pay particular attention to excavation, spoil, rock, service connections, wastewater, crane costs, traffic control, utility upgrades and authority conditions.

11. Can the quote be compared with another builder's quote?

Request a schedule that separates design and approvals, dwelling construction, site works and foundations, delivery or site logistics, service connections, external completion work, exclusions, owner responsibilities and unknown items.

If the builder will only provide a single headline number, you cannot tell whether the quote is cheaper or simply incomplete. The quote scope checker can help separate written inclusions from unanswered scope.

12. What contract will be used?

Ask for the draft contract and all schedules before the signing appointment. Confirm that plans, specifications, price, parties, site, timing, payment stages, approval responsibility, variations, delays, insurance, defects and termination are included.

State thresholds and mandatory terms differ. NSW publishes contract requirements and a homeowner checklist for residential building work. Consumer Affairs Victoria recommends comparing quotes on the same plans and specifications and including detailed selections in the contract. Use the Australian building-contract checklist for the next review, and obtain legal advice where the contract or offsite supply arrangement is unclear.

13. What does the preliminary fee buy?

If the builder charges for a site review, concept, planning check or drawings, ask what documents you will receive, whether the fee is refundable or credited to the build, who owns and may reuse the design, whether the fee authorises any building work, which assumptions can still change the main price, and what happens if approval or finance is not obtained.

A small preliminary agreement can still create important obligations. Do not treat it as a harmless reservation payment.

14. How are deposit and progress payments set?

Ask which state rule and contract type the payment schedule relies on. Tie every progress claim to work or materials that can be identified and verified. For factory construction, clarify inspection access, photographs, certificates, ownership of materials and what happens if the module is complete before the site is ready.

Confirm the lender can work with the proposed offsite stages before signing. A normal construction lender may require a licensed builder, approved plans, a valuation and conventional progress evidence.

15. What insurance and warranty evidence will be provided?

Ask which statutory home warranty, indemnity or compensation scheme applies to the exact contract, and request required evidence before payment. Also ask about public liability, contract works, transit, installation, product and professional insurance where relevant.

Separate statutory protections from the builder's own written warranty and appliance warranties. Ask who handles defects after handover, the reporting process and the expected response time.

16. What is the realistic program?

Request one program covering site investigation, design, approval, selections, manufacture or site construction, service work, delivery, inspection and handover. Ask which dates are estimates, what must happen before the clock starts, and which current workload assumptions support the programme.

A short factory build time does not measure the whole project. Approval, site work and service delays can sit outside the advertised lead time.

17. What will I receive at handover?

Define practical completion and the documents due before final payment. Depending on the project, the handover pack may include approved plans, engineering, inspection records, trade certificates, product warranties, manuals, keys, commissioning records, a defects list, and an occupancy or completion document.

Do not accept a dwelling that is physically present but cannot yet be lawfully occupied or connected as the agreed complete result.

18. Can I inspect comparable completed projects and speak with owners?

Ask for projects with a similar construction method, intended use, approval pathway, site access and delivery distance. A display model proves little about difficult ground, backyard access, authority changes or after-sales service.

When speaking with an owner, ask what changed after contract, which costs sat outside the quote, how communication worked and how defects were resolved. Confirm that the reference relates to the same contracting entity.

A simple quote-comparison sheet

Create one column for each builder and record evidence, not only sales answers.

Mark an unanswered line as unknown, not included. Add a project contingency only after the known exclusions and allowances are visible.

Red flags that justify a pause

• The business says every model is “council approved” without reviewing the property.
• The name on the quote, licence, invoice and bank account does not match.
• A cabin, studio or module is presented as a lawful dwelling without a project-specific pathway.
• “Turnkey” replaces a detailed scope and exclusions schedule.
• The builder cannot explain who handles foundations, services, installation or final certification.
• A deposit is requested before you receive the contract and required insurance evidence.
• Progress payments are tied only to dates or vague factory stages.
• Important promises appear in sales messages but not the contract documents.
• The programme ignores approvals, site work, delivery access or current workload.

Where Zinc Studio may fit

If the brief is closer to a design-led prefab cabin or compact premium dwelling than a basic site-built granny flat, Zinc Studio's directory profile is one option to compare. Confirm directly whether Zinc services the location and intended use, and ask for the same approval, site, delivery, installed-scope, price and handover evidence listed above. This is a featured commercial pathway, not an independent ranking or an approval recommendation.

Useful next steps

• Browse modular home builders
• Browse all Australian builders
• Granny-flat cost guide
• Prefab granny-flat buyer guide
• Tiny house versus granny flat
• Building-contract checklist
• Whole-project budget planner

Sources

• NSW Planning: secondary dwellings
• NSW Government: home building contract checklist
• NSW Government: choosing a builder
• Planning Victoria: small second homes
• Consumer Affairs Victoria: getting building quotes
• Consumer Affairs Victoria: building contracts checklist
• Queensland Planning: secondary dwellings
• QBCC: tiny homes, prefab and modular buyer guidance

Disclaimer

This checklist is general buyer information, not legal, planning, building, financial, valuation or insurance advice. Definitions, licence requirements, contracts, deposits, insurance, approvals and handover documents differ by state and project. Confirm the exact property, intended use, contracting entities and current requirements with the relevant authorities and qualified advisers before signing or paying.

Last updated 24 August 2026.