Home extension calculator
What would an extension cost, and add?
Build, fees and interest for the extension you have in mind, against what it adds to your home and what moving would cost instead.
Your property
So it saves to the right property in your plan, and a builder can look at your home.
Type of extension
What it's for
Size30 m²
10 m²120 m²
Build cost per m²$2,800
Your builder's quote is the real number. Second storeys usually cost more per m² than ground floor.
$1,800$6,000
How you'd pay for it
Value (optional)
Add both to see whether it adds more than it costs. The value after is your figure: check what extended homes nearby have sold for.
What your home is worth today
$
What it would be worth after
$
Adjust the other costs
Fees
Other costs
Finance (assumptions)
Compared with moving
The interest rate is an assumption. A mortgage broker can tell you what applies to you.
What it costs
Build (30 m² at $2,800/m²)$84,000
Architect or designer$15,000
Council and approval fees$12,000
Structural engineer$8,000
Building insurance$2,000
Temporary works$5,000
Landscaping and making good$8,000
Total before interest$134,000
Interest (6.5% on 80% for 8 months)$4,645
Total cost$138,645
Value
All-in cost per m²$4,622
Value addedAdd the value now and after
Extend or move?
Moving has its own costs: stamp duty on the next home, agent fees on this one, legal fees and the removalist.
What moving would cost$45,000
Total cost of the extension$138,645
Add the value now and after to compare properly
Before you start
Concept design and a feasibility checkArchitect or designer
Approval pathway (it varies by state and council)Council or certifier
Structural check, especially for a second storeyStructural engineer
Fixed-price quotes from at least three buildersBuilder
Finance for the buildMortgage broker
Insurance during the build, and where you live meanwhileInsurer and builder