Knock Down Rebuild Cost Calculator

Add quoted rebuild costs and holding expenses to compare your project budget with cash and proposed finance.

Your rebuild costs

Enter quotes including tax. Leave unknown costs blank and enter 0 for costs that do not apply.

Building quote ($)

Use the full building quote. Enter separate costs below only when excluded from it.

Demolition ($)

Site works ($)

Include excavation, drainage and retaining work outside the building quote.

Other project costs

Approvals ($)

Professional fees ($)

Include design, surveying and engineering fees outside other quotes.

Service connections ($)

Include disconnection and reconnection charges outside other quotes.

Finishing work ($)

Include excluded driveways, landscaping, fencing and fit-out.

Other project costs ($)

Holding costs

Monthly accommodation ($)

Include rent and storage paid while the home is unavailable.

Monthly finance costs ($)

Enter an average cash cost. Interest and repayments are not calculated here.

Holding period (months)

The 12-month starting period is editable. Include time before and after construction if needed.

Contingency and funding

Contingency (%)

The editable 10% allowance applies to direct project costs, excluding holding costs.

Available cash ($)

Enter cash available for this project after other commitments.

Proposed project lending ($)

Use funds available for project costs, after any existing debt payout.

View your budget

Your rebuild budget

Enter your quotes

Entered project budget: $0; Includes entered costs and contingency. Blank costs are excluded, so this can be an incomplete budget.
Contingency allowance: $0
Total holding costs: $0
Cash and proposed lending: $0
Funding difference: $0

Balanced on entered costs. 10 cost lines left blank and excluded. Blank funding excluded.

Itemised budget

Cost	Amount
Building quote	Not entered
Demolition	Not entered
Site works	Not entered
Approvals	Not entered
Professional fees	Not entered
Service connections	Not entered
Finishing work	Not entered
Other project costs	Not entered
Direct project costs	$0
Contingency	$0
Accommodation over holding period	$0
Finance over holding period	$0
Project budget	$0
Funding shortfall	$0
Funding surplus	$0

Costs Beyond the Build Contract

A knock down rebuild budget adds demolition and other excluded costs to the building quote. Enter each amount once, including any tax you must pay.

Keep demolition, site works, approvals, professional fees and service connections separate when the building contract excludes them. Finishing work can include driveways, fencing and landscaping. Use other project costs for remaining expenses outside those lines.

The New South Wales Government's rebuild planner explains how site conditions and quote exclusions change a rebuild budget. Land purchase costs and an existing mortgage payout need a separate allowance if they apply.

Holding Costs During the Rebuild

Holding costs equal monthly accommodation plus entered monthly finance costs, multiplied by the holding period. Include the full period the client must fund, including delays or time before construction starts.

Enter rent and storage in accommodation. Use an average monthly finance cash cost for the project period. Include continuing existing mortgage payments only if the budget must fund them, and avoid adding interest twice.

For example, $2,400 in monthly accommodation and $1,800 in monthly finance costs total $50,400 over 12 months. Three extra months add $12,600. Construction interest changes as funds are drawn, so this calculation uses the monthly amount you enter.

Contingency and the Funding Gap

The calculator applies your contingency percentage to direct project costs, then adds holding costs. Cash plus proposed project lending is compared with that total to show a surplus or shortfall.

The 10% starting allowance is editable. The Victorian Government's guidance on unexpected building costs explains why a contingency belongs in the budget. Choose an allowance for the actual project risks and include known expenses as cost lines.

In a hypothetical example, a $550,000 build plus $25,000 demolition and $20,000 site works starts at $595,000. Add $5,000 approvals, $15,000 professional fees, $8,000 services and $7,000 finishing work to reach $630,000 in direct costs. Enter 0 for other project costs.

A 10% contingency adds $63,000. With $50,400 in holding costs, the entered project budget is $743,400. Cash of $100,000 and proposed lending of $600,000 leave a $43,400 shortfall.

A balanced total does not establish that cash is available when each payment falls due. Allow for lender drawdown conditions, existing debt and funds needed before the first construction payment.

Estimates Versus Quotes

This knock down rebuild cost estimate depends on the quotes entered and what they include. Blank lines are excluded and counted beside the funding result, so a low total can still omit major costs.

A single cost per square metre cannot account for every site's access, ground conditions or demolition hazards. The client's design and selections also change the price. Replace early allowances with itemised local quotes as the project becomes defined.

The Australian Government's guide to building a house explains comprehensive quotes and allowances for unexpected work. Use the completed budget alongside the proposed finance terms before committing to the rebuild.

Bulma Team

When a client scenario hinges on lender policy, Bulma gives mortgage brokers source-cited AI answers to compare and verify before advising.