Granny Flat Builders: How to Find and Compare the Right Builder

Specialist granny flat builders vs general builders

The first decision most homeowners face is whether to use a specialist granny flat builder or a general residential builder. Both can deliver a quality result, but there are meaningful differences in how they operate.

Specialist granny flat companies focus exclusively — or primarily — on secondary dwellings. They typically offer a range of standard floor plans optimised for common lot sizes and the 60sqm internal floor area cap that applies in NSW under the Housing SEPP. Many handle the entire process from design through to council approval and handover, which is what the industry calls a turnkey build.

The advantage of a specialist builder is process efficiency. They have built hundreds or thousands of granny flats, they know the approval pathways intimately, and their supply chains are optimised for the specific materials and trades involved. They can often quote more accurately because they have deep data on what things actually cost.

The disadvantage is flexibility. If you want a highly customised design, unusual materials, or a complex site that does not suit their standard approach, a specialist builder may either decline the job or charge a significant premium.

General residential builders bring broader construction experience and may offer more design flexibility. A good general builder with granny flat experience can deliver an excellent result — particularly for custom builds or complex sites. However, a general builder who has never navigated a CDC application or does not understand the specific setback requirements for secondary dwellings can cost you time and money.

The key question to ask any general builder is: How many granny flats have you completed in the past 12 months, and can I see them?

What to look for in a quality granny flat builder

Correct licensing for your state

Builder licensing requirements differ across Australian states. Using an unlicensed builder is not just risky — it can void your insurance protections and create compliance issues that affect the property for years.

• NSW: Builders must hold a licence from NSW Fair Trading. For work over $5,000, a contractor licence is required. For work over $20,000, Home Building Compensation (HBC) insurance is mandatory. Verify licences at the NSW Fair Trading licence check tool.
• Victoria: Builders must be registered with the Victorian Building Authority (VBA). Domestic building insurance is required for work over $16,000. The VBA maintains a public register of registered builders.
• Queensland: A QBCC (Queensland Building and Construction Commission) licence is required. The QBCC licence search is publicly available. Home warranty insurance applies to work over $3,300.
• Western Australia: Builders must be registered with the Building Commission. Registration can be verified through the WA Department of Mines, Industry Regulation and Safety.
• South Australia: A building work contractor licence from Consumer and Business Services is required.

Always verify licensing independently — do not rely on the builder telling you they are licensed. Every state maintains a free public register.

A clear, detailed contract

A quality builder will provide a detailed fixed-price contract that specifies:

• The full scope of works, including what is and is not included
• A construction timeline with key milestones
• A payment schedule tied to those milestones — never pay more than 10% upfront (in NSW, deposits are capped at 10% of the contract price or $20,000, whichever is less)
• Specifications for all major materials, fixtures, and finishes
• The process for handling variations (changes to scope)
• Defect liability period and dispute resolution process

If a builder is reluctant to put details in writing, that tells you something important about how they operate.

Completed project examples and references

Ask to see completed granny flats — ideally in person, not just in photographs. Photos on a builder's website show their best work in ideal conditions. Visiting a completed build lets you assess the quality of finishes, the feel of the space, and how the granny flat sits on the property.

Ask for references from recent clients and actually call them. Ask about the build process, how the builder handled problems, whether the project ran to budget and timeline, and whether they would use the same builder again.

Understanding of approval pathways

A good granny flat builder should be able to explain the approval pathway that applies to your property — whether that is a CDC (Complying Development Certificate) in NSW, accepted development in Queensland, or a building permit in Victoria. They should know the key criteria, the likely timeline, and any potential issues with your specific site.

Builders who are vague about approvals or who promise that "council is no problem" without assessing your property are a red flag. Approval requirements depend on your specific lot — its size, zoning, overlays, and location relative to flood zones, heritage areas, and bushfire-prone land.

Red flags when choosing a granny flat builder

The granny flat industry, like all residential construction, has its share of operators who cut corners. Watch for these warning signs:

Unusually low quotes. If one quote is 20–30% below others for the same scope, something is missing. Common tactics include quoting without site costs, excluding utility connections, or specifying lower-grade materials. Compare quotes on a like-for-like basis using a detailed scope of works.

Pressure to sign quickly. "This price is only valid until Friday" is a sales tactic, not a construction reality. A quality builder will give you reasonable time to review a quote and compare options. Rushed decisions on a $150,000+ project are how problems start.

No fixed-price contract. Cost-plus contracts transfer all the risk to you. For a standard granny flat build, there is no good reason not to offer a fixed price. If a builder insists on cost-plus, ask why — and consider walking away.

Requesting large upfront payments. NSW law limits deposits to 10% of the contract price or $20,000, whichever is less. Builders who ask for more than this — or who want large progress payments before work reaches defined milestones — may have cash flow problems.

No Home Building Compensation insurance. In NSW, HBC insurance is legally required for residential building work over $20,000. A builder who cannot provide proof of current HBC cover either does not have it (illegal) or has let it lapse (which suggests financial trouble).

Unwillingness to provide references. Every established builder should have satisfied clients willing to speak about their experience. A builder who cannot or will not provide references has something to hide.

How much do granny flat builders charge?

Granty flat building costs vary significantly depending on the build type, size, finish level, and your location. As a broad guide based on Q2 2026 pricing:

• Studio granny flat (under 40sqm): $80,000–$150,000 ex GST
• 1-bedroom granny flat (35–50sqm): $100,000–$200,000 ex GST
• 2-bedroom granny flat (50–60sqm): $130,000–$280,000 ex GST

These ranges include design, approvals, and construction for a standard turnkey build. Site costs, utility connections, and council contributions are typically additional. For a detailed breakdown of what drives costs, see our granny flat cost guide.

Kit home and flat-pack options start lower — from around $40,000 for materials — but the total project cost including slab, labour, approvals, and fit-out is substantially higher than the kit price alone.

Comparing granny flat builders: a practical checklist

When you are ready to compare builders, work through this checklist for each one:

1. Verify their licence on your state's public register
2. Request proof of insurance — HBC/home warranty and public liability
3. Get a detailed written quote with a full scope of works
4. Ask how many granny flats they have completed in the past 12 months
5. Visit at least one completed project in person
6. Call two or three references and ask about budget, timeline, and defects
7. Check online reviews — but weight them appropriately (some are incentivised)
8. Ask about their approval process — do they handle CDC/DA, or is that your responsibility?
9. Clarify what is excluded from the quoted price
10. Ask about their defect liability period and how they handle post-handover issues

Getting three quotes is standard practice. But do not choose on price alone — the cheapest quote often ends up being the most expensive project once variations, delays, and defects are factored in.

Granny flat builder types by build method

Different builders specialise in different construction methods. Understanding these helps you find the right match for your project:

Turnkey builders handle everything from design to handover. They manage approvals, construction, and final certification. This is the most common model for granny flat construction and suits homeowners who want a single point of accountability.

Kit home suppliers provide pre-cut materials and plans. You arrange assembly — either as an owner-builder or by hiring a separate builder. Kit prices start low but the total project cost is significantly higher once you add the slab, labour, services, approvals, and fit-out.

Modular builders construct your granny flat in a factory, then transport the modules to your site for assembly. This can reduce on-site construction time to as little as one to two weeks, but transport, cranage, and site access constraints can add cost.

Transportable builders deliver a complete unit to your site. This is the fastest on-site option but requires suitable access for delivery — typically a clear path at least 3.5 metres wide with no overhead obstructions.