Granny Flat Quotes: Find the Full Project Cost Before You Sign

A low granny-flat price is not enough to establish a good purchase. First establish what will be delivered, where it can lawfully be installed, and which costs remain with the owner. A factory shell, an installed dwelling and a completed site ready for its intended occupation are different scopes.

In Joey’s September site-inspection script, the practical question is (translated from Chinese): what is it built with, and what does that specification cost? That is a better starting point than comparing headline prices per square metre.

Make every tender describe the same building

Give each builder the same drawings and ask for a written inclusions and exclusions schedule. Record the wall, roof and floor systems; windows; insulation; waterproofing; kitchen and bathroom fittings; heating; hot water; finishes; and external work. “Premium finish” is not a measurable specification.

For an unfamiliar product, ask for the evidence that supports its proposed use and have the relevant building professional assess it. A certificate must apply to the product, installation and performance being claimed. A photograph of another completed home is not a substitute.1

Bring the site costs into the comparison

Arrange the information needed to assess the ground, levels, access and existing structures. Ask whether the quote includes engineering, footings, retaining work, drainage, tree-related constraints, demolition and reinstatement. Identify what remains provisional and what evidence will fix the price.2

A delivered module also needs a transport and placement plan. Check road and site access, lifting arrangements, temporary works, weather protection, connections and responsibility for damage during each stage. The ABCB’s modular-construction guidance treats offsite production as part of a complete building process, not a shortcut around compliance.3

Write a complete cost ledger

Use the following headings before comparing totals:

investigation, survey, design, engineering and permits;
the contracted building and finishes;
preparation, access, delivery and installation;
electricity, water, sewerage and stormwater work;
outdoor paths, fences, landscaping and reinstatement;
inspections, certificates, defects and handover;
finance and holding costs, relevant taxes and a reasoned contingency.

Ask whether GST is included in each quote and whether professional fees are inside or outside it. Where a builder says “by owner”, name the person who will procure and coordinate that item. An omitted task is still a project cost.

Check the July 2026 insurance change

For eligible Victorian domestic building contracts signed from 1 July 2026, the Home Warranty scheme replaces the old DBI approach. Consumer Affairs Victoria identifies cover for homes up to three storeys where the contract exceeds $20,000, with protection that can apply even while a builder is still trading. Confirm the notice of cover and the conditions relevant to your contract.4 5

Contracts signed before the change have a different insurance pathway. Keep the actual contract date and policy with the file, rather than copying an old checklist’s threshold into a new project.6 Do not infer that a transport-only purchase or every imported component has identical coverage: have the contractual scope and proposed insurance checked together.

Link payments to verifiable work

Check the builder’s registration and authorised work category, then review the contract’s payment stages, variations and exclusions.7 Consumer Affairs Victoria’s payment guidance is particularly relevant when a supplier asks for substantial money before on-site work exists. Insurance may not cover work paid for before completion.8

At each payment stage, establish what work has actually been completed and which contractual and inspection requirements apply. A video from a factory may help identify a component, but it does not establish that every item in a progress claim is payable.

Inspect work in progress as well as the display home

With permission, inspect relevant work at different stages and use an independent qualified inspector where appropriate. Ask to see how framing, weather protection and services correspond to the approved documents. If there are signs of damp, deterioration or unexplained repairs, request investigation and rectification evidence rather than accepting a cosmetic finish as resolution.

Take the quote back to the intended site and operating plan. Our utility-meter guide, liveability checklist and imported-home compliance guide cover common gaps between a sale brochure and a usable home. Begin a site review through the granny-flat service.

Questions buyers ask

Can I compare granny-flat quotes by price per square metre?

Only after making the building specification and site scope comparable. A cheaper rate may omit transport, ground work, services, approvals or finishes.

Does a display home prove the supplied building will comply?

No. The proposed building needs applicable approval and evidence for its actual products, installation and site. Inspecting relevant work and reviewing the documents answer different questions.

Should a new September 2026 contract use an old DBI checklist?

Check the current Home Warranty rules and the actual contract date. Older contracts and new contracts may follow different insurance arrangements; obtain the relevant notice or policy rather than assuming coverage.

Source videos and verification scope

This article develops practical questions raised in the published videos below and checks them against the sources cited here. Case prices, forecasts and broad claims in a video do not establish the result for another property.