Knock-Down Rebuild Cost Calculator Sydney 2026 — Free NSW Tool

Knock-down rebuild cost calculator — Sydney

If you already own your home and you're thinking about demolishing it to build new on the same land, the calculator below tells you what you can afford. Knock-down rebuild (KDR) is different from a renovation, different from a development, and different from buying a new home — you keep your land, you keep your suburb, you start the dwelling from zero. No acquisition stamp duty applies (you already own the land). The financing structure is a construction loan secured against the property, usually drawing on releasable equity in the current home plus a cash injection. Pre-configured for a typical Sydney KDR of a $1.5M existing home rebuilt to a $1.5M new home.

Upfront component	AUD
Cash deposit	$100,000
Stamp duty	$0
LMI(Not required (LVR ≤ 80%))	$0
Legals + inspection	$3,300
Total upfront cash	$103,300

Upfront component

AUD

Cash deposit

$100,000

Stamp duty

LMI(Not required (LVR ≤ 80%))

Legals + inspection

$3,300

Total upfront cash

$103,300

Lever	-10%	-5%	Base	+5%	+10%
Sale price	0%	0%	0%	0%	0%
Build cost	0%	0%	0%	0%	0%
Duration	0%	0%	0%	0%	0%
Overrun buffer	0%	0%	0%	0%	0%

Lever

-10%

-5%

Base

+5%

+10%

Sale price

Build cost

Duration

Overrun buffer

Rate	Quick (library)	Active value
Construction rate (AUD/m²)	$4,095/m²	$4,095/m²
Interest rate (decimal, e.g. 0.085)	9.5%	9.5%
Loan-to-cost ratio (decimal, e.g. 0.65)	65%	65%

Rate

Quick (library)

Your override

Active value

Construction rate (AUD/m²)

$4,095/m²

Interest rate (decimal, e.g. 0.085)

9.5%

Loan-to-cost ratio (decimal, e.g. 0.65)

65%

Bucket	Quick (derived)	Active value
Acquisition (land, stamp duty, legals)	$2,106,512	$2,106,512
Planning & design	$97,278	$97,278
Construction	$1,154,626	$1,154,626
Professional fees	$34,639	$34,639
Finance	$268,011	$268,011
Holding	$42,900	$42,900
Marketing & selling	$83,100	$83,100
Contingency	$136,964	$136,964
Taxes & duties	$36,364	$36,364
Total development cost (reconciled)	$3,960,393	$3,960,393

Bucket

Quick (derived)

Your override

Active value

Acquisition (land, stamp duty, legals)

$2,106,512

Planning & design

$97,278

Construction

$1,154,626

Professional fees

$34,639

Finance

$268,011

Holding

$42,900

Marketing & selling

$83,100

Contingency

$136,964

Taxes & duties

$36,364

Total development cost (reconciled)

$3,960,393

How knock-down rebuild financing works

Most banks lend against KDR projects as a 'construction loan' secured by the existing property plus the to-be-built dwelling. Your borrowing power is driven by (1) releasable equity in the current home — typically 80% of current value minus any existing mortgage, (2) any cash injection you bring, and (3) your serviceability against the new mortgage. The bank pays the demolition contractor in stage 1, then the builder in progress draws as construction advances. You service interest-only during construction, then roll to P&I when the home is complete.

When KDR makes more sense than renovating

If your renovation budget is approaching 50% of post-reno home value, KDR usually wins — you get a brand-new home with full warranty, modern thermal performance, modern layout, and no concealed defects. Reno is better when (a) you love the existing home and only want to upgrade specific rooms, (b) the existing structure has heritage value that converts to sale-price premium, or (c) you're tight on time (reno is typically faster than DA + demo + build cycle).

Stamp duty advantages of KDR

This is the big one. Because you already own the land, there's no acquisition stamp duty — you skip an entire NSW transaction cost that would apply if you sold + bought. For a $1.5M property in Sydney, that's $67,000+ in stamp duty you don't pay. That's the cost of a kitchen renovation right there.

Timeline and what to budget

Typical Sydney KDR: 2–3 months for DA + construction certificate, 1 month for demolition + site prep, 9–14 months construction. Total 12–18 months from start to keys. Budget the rebuild at $2,800–$5,500/m² depending on quality, plus $25k–$45k for demolition (more if asbestos), plus the usual soft costs. Use the calculator below to model the full stack including releasable equity and finance interest.

Frequently asked questions

Is knock-down rebuild cheaper than buying a new home?

Often yes — you save the stamp duty on land acquisition (typically 4–5% of the property value in NSW), you avoid agent fees on the sale of your current home (2–3% of the sale price), and you avoid moving costs. For a $1.5M Sydney property, that's $90k–$120k in transaction cost savings versus selling and buying.

Do I need to live somewhere during the rebuild?

Yes — most KDR programs are 12–18 months. Most homeowners either rent locally or stay with family. Budget $700–$1,200/wk for a comparable Sydney rental over the construction period. Some lenders will include rental cost in serviceability calculations.

Can I get NSW First Home Buyer assistance on a KDR?

Generally no — FHB assistance applies to acquisition stamp duty (which you don't pay) and the First Home Owner Grant for new builds (which usually requires the property to be your first home, not your second build). Check eligibility carefully with Revenue NSW — exceptions exist for some scenarios.

How much does demolition cost in Sydney?

Sydney house demolition typically runs $25k–$45k for a standard fibro/brick veneer home, $45k–$80k if asbestos abatement is needed, $80k+ for complex sites (sloping, heritage adjacency, tight access). Get 2–3 quotes from licensed demolition contractors — confirm the quote includes waste disposal, site clearance, and council bond.

What happens to my existing mortgage during the rebuild?

The bank usually pays it out and re-issues a new construction loan against the property. The new loan may have a higher rate during construction (interest-only) then revert to standard P&I when the home is complete. Discuss break costs and conversion structure with your broker before committing.

Knock-down rebuild cost calculator — Sydney

Deal basics

Affordability — knock-down rebuild

What this deal is telling you

Not feasible at current inputs (-40.5% margin on cost)

Build rate $4,095/m² is 41% above the Sydney median for house_and_land

Contingency at 3.4% is thin for an early-feasibility project

Here's how the numbers were built

Revenue

Construction cost

Acquisition

Soft costs, finance & contingency

The bottom line

What would change the answer

Cost breakdown

Scenarios — how resilient is this deal?

Sensitivity — which levers move the needle

What scale does this site need?

Pro Mode — override anything (optional)

Underlying rates

Cost buckets

Construction BoQ — trade-level drill-down (optional)

Takeoff & assemblies — bottom-up line items (optional)

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How knock-down rebuild financing works

When KDR makes more sense than renovating

Stamp duty advantages of KDR

Timeline and what to budget

Frequently asked questions

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