Questions to Ask Before You Sign With a Granny Flat Builder

Signing a building contract is a big moment, and a granny flat is no small spend. The right granny flat builder questions, asked before you sign, are the cheapest insurance you will ever buy. They sort the genuine fixed quotes from the ones that look cheap until the extras land.

We have built modular and transportable homes across NSW for over 30 years, so we have seen where people get caught out. Here are the exact questions to put to any builder before you commit, and why each one matters.

Is the price truly fixed, and what could change it?

Plenty of quotes look low because they are not complete. Ask whether the price is a genuine fixed price for the whole job, and what specific things could push it up. A straight answer here tells you a lot about the builder.

The honest reply is that site conditions can move a price. In Sydney, the two big multipliers are hitting rock or sandstone during excavation and how far your services have to run to the sewer. A good builder will explain how those are handled in the contract rather than burying them as a surprise later.

What is actually included?

The word inclusions hides a lot. Get a written list and check it covers the things that turn a shell into a finished home.

• Flooring, paint, and a complete kitchen with benchtops and appliances.
• A finished bathroom and laundry, not just rough-ins.
• Site preparation, which can run roughly $3,000 to $10,000.
• Service connections for water, power and sewer, often around $15,000 to $30,000.
• Approval and certification costs, typically $5,000 to $11,000.
• External works like a driveway, paths and landscaping, which can be $8,000 to $23,000.

If any of these sit outside the quote, that is fine, as long as you know up front. The trap is assuming they are included when they are not.

How are site costs assessed?

Site costs are where budgets blow out. Ask how the builder assesses your block before quoting, and whether site costs are estimated or fixed. A builder who inspects the site, checks the soil, and looks at where your services run is giving you a more reliable number than one who quotes off a floor plan alone.

For the full picture of what site work involves, our breakdown of granny flat costs in NSW for 2026 lays out the typical ranges so you can sense-check any quote you receive.

What is the timeline, start to finish?

Ask for a realistic timeline and what the stages are. With a traditional on-site build, you are looking at months of trades coming and going, weather delays and a backyard that is a worksite the whole time.

A modular build is different. Our homes are built in the factory in about eight weeks, then transported and installed on site in about two days. That means the disruptive part on your property is measured in days, not months. Our step-by-step build process shows exactly how it runs from first call to handover.

Who handles the approvals?

Approvals can be confusing, so ask whether the builder manages them for you or leaves you to sort it out. Most blocks of 450 square metres or more can go through the Complying Development Certificate pathway, assessed by a private certifier in about 10 to 20 business days, while sites that do not qualify need a council Development Application.

A builder who handles the approval path, or at least guides you through it, saves you a lot of stress. Our guide to how granny flat approval works in NSW explains both pathways so you know what is involved.

Are you licensed, and what warranty do I get?

This one is simple but essential. Ask to see the builder's licence and ask what warranty comes with the home. In NSW, residential building work over a certain value requires the right licensing and home building insurance, and a reputable builder will have no problem showing you.

A good warranty backs the structure and the workmanship for years after handover. If a builder is vague about their licence or their warranty, that is your answer right there.

Frequently asked questions

What is the most important question to ask?

Whether the price is genuinely fixed and what could change it. That single answer reveals how complete the quote is and how the builder handles site risk.

Should the builder handle council approvals?

Ideally yes, or at least guide you through it. Knowing whether your block suits the CDC pathway or needs a council DA is part of getting the job right.

How long should a granny flat take to build?

A modular home is built in the factory in about eight weeks and installed on site in about two days, so the disruption to your property is very short compared with a traditional build.

Ask us anything

We would rather you asked these questions than skipped them, because the answers are part of doing the job properly. If you want straight answers and a real fixed quote, take a look at our modular granny flats and studios and our frequently asked questions. When you are ready, get in touch and put every one of these questions to us.