What a knock-down rebuild actually costs in Sydney

Someone rings and asks what a knock-down rebuild costs in Sydney. The honest answer is a range so wide it sounds evasive — somewhere between $900,000 and $4 million. That's not a dodge. It's that the question is usually asking about the build, and the build is not the cost.

So here's the whole stack for a typical Sydney knock-down rebuild in 2026, in the order you'll actually pay it.

Demolition: $25,000 to $60,000

A straightforward single-storey weatherboard on a flat block with truck access sits at the bottom of that. A two-storey brick house on a narrow Inner West lot where the machine can't get past the side setback sits at the top.

Two things move this number more than size. Asbestos is the first — anything built before about 1990 needs a survey, and if bonded sheeting turns up in the eaves, wet areas or under the vinyl, licensed removal adds $8,000 to $25,000. The second is access. A block where the excavator can drive in and the truck can turn is a different job to one where everything comes out through a 3-metre gap by hand.

Budget the asbestos survey ($800–$1,500) before you budget anything else. It's the cheapest way to find out whether your demolition number has a second digit.

The build: $2,900 to $5,500 per square metre

This is the number everyone compares, and the one worth being careful with.

For a new detached house in Sydney metro in 2025–26:

• Standard custom build — $2,900 to $3,900/m²
• High-end custom — $3,400 to $5,500/m²
• Luxury — $6,000 to $11,000/m²

A 280 m² house at $3,400/m² is $952,000. The same house at $4,800/m² is $1.34 million. Same footprint, same suburb — the difference is entirely specification and site.

Two things push you up the range regardless of taste. Sloping sites add 10–25% before you've chosen a tap, because you're paying for retention, drainage and often piling. Coastal exposure within a kilometre of open ocean adds 5–15% across every reinforced concrete element in corrosion allowance.

The eight items outside the build quote

This is where people get caught. None of the following is usually in the builder's number, and together they routinely add 25–35% on top.

Demolition — covered above, unless your contract explicitly includes it.

Consultants — architect or building designer, structural engineer, surveyor, certifier, sometimes a planner. On a custom Sydney home, $45,000 to $120,000 depending on how much design you're buying.

Council DA and contributions — application fees, plus s7.11 or s7.12 developer contributions. On a knock-down rebuild the contributions are usually modest because you're replacing one dwelling with one dwelling, but the DA fee, notification and assessment still run $5,000 to $20,000. If you go the complying development route through a private certifier instead, it's faster and often cheaper — but only if your design fits inside every control.

HBCF — Home Building Compensation Fund insurance, mandatory in NSW on residential work over $20,000. The builder pays it and passes it through: 0.3% to 1.5% of contract value. On a $1.2 million build, $3,600 to $18,000.

Service connections and disconnections — capping the old sewer and water, disconnecting power and gas, then reconnecting to the new dwelling. Ausgrid and Sydney Water charges together are commonly $8,000 to $30,000. If your street needs a new pit or the main is on the far side, more.

Site costs — excavation, retention, drainage, piling if the geotech calls for it. On a flat sand block, $15,000. On a steep Northern Beaches site with sandstone, $150,000 or beyond. Get the geotechnical report before you sign anything with a fixed price, because a builder pricing without one is guessing and the guess will be conservative in their favour.

Landscaping and driveway — almost never in the build contract. $30,000 to $150,000. It's the one people defer, then discover the occupation certificate depends on it.

Rent while you build — 12 to 18 months somewhere else. At $1,200 a week that's $62,000 to $94,000, and it's real money even though it never appears on a quote.

Putting it together

A 280 m² high-end custom home on a moderately sloped Sydney block, 2026:

| Item | Cost | |---|---| | Demolition (incl. asbestos) | $45,000 | | Build — 280 m² @ $4,200/m² | $1,176,000 | | Consultants | $85,000 | | Council, DA, contributions | $14,000 | | HBCF | $9,000 | | Service connections | $18,000 | | Site costs and retention | $70,000 | | Landscaping and driveway | $65,000 | | Contingency @ 8% | $118,000 | | Total, excluding rent | $1,600,000 |

The build quote in that table is $1.176 million. The project is $1.6 million. That gap — 36% — is the entire reason people feel blindsided halfway through.

The contingency line is not optional

Eight percent is the floor on a knock-down rebuild, and only because demolition removes most of the unknowns that plague renovations. If you're keeping any part of the existing structure, go to 15%.

We've never run a project where the contingency went entirely unused. Not one.

What actually reduces the number

Not finishes. People assume the savings live in tapware and stone, and there's maybe $40,000 there on a million-dollar build.

The real savings are structural, and they're all decided before you lodge:

Simplify the roof. Every change of plane costs money in framing, flashing and labour. A complex articulated roofline can add $60,000 over a simple one on the same floor area.

Keep wet areas stacked and adjacent. Bathrooms above bathrooms, kitchen backing onto the laundry. Plumbing runs are cheap in straight lines and expensive in dog-legs.

Don't fight the slope. A house that steps with the land costs a fraction of one that requires the land to be flattened. Cut and fill is one of the great silent budget killers on Sydney blocks.

Decide everything before you start. Variations after the contract is signed are priced without competitive tension, and they compound. A client who finalises selections pre-contract will land closer to their number than one who is still choosing tiles in month four — every single time.

The question to ask a builder

Not "what's your per-square-metre rate." That number is close to meaningless without knowing what sits inside it.

Ask instead: "What's in your quote, and what will I be invoiced for separately?" A builder who answers that clearly, in writing, with the exclusions listed, is telling you more about how the project will run than any headline rate.

If you want to model your own numbers, our [build cost calculator](/construction/propdev) runs the full stack — construction, duty, council, HBCF, finance and contingency — and every figure is editable.