by: Martina Hayes
Calculate your house extension budget
Is your family outgrowing your current home? Whether you’ve welcomed a new bundle of joy, need a home office or want to accommodate extended family, the reasons for needing more space are endless.
When it’s time to expand, you typically have two choices:
- move to a bigger house, or
- extend your existing one
to meet your family’s needs.
Why Choose a House Extension?
If your current home is in a convenient location—close to work, schools, and the amenities you love—extending it might be the better option. In essence, depending on your property, you can:
- Extend outward into the backyard, or
- Build upward by adding a second storey.
But how much does it cost to add space to your home? Let’s break it down so you can budget effectively.
Overview of House Extension Cost Sydney
Use the table below to calculate your house extension cost in Sydney. Start by deciding whether to expand outwards or upwards, then calculate the area you wish to extend. Most importantly, if you’re adding a kitchen or bathroom, include those costs too.
| Price per additional square metre | Add for a new kitchen | Add for each bathroom | |
| Ground Floor Extension | $2,600 – $3,200 | $50,000 – $85,000 | $35,000 – $50,000 |
| First Floor Addition | $4,000 – $4,500 | $50,000 – $85,000 | $35,000 – $50,000 |
This information is for guidance only. The prices apply to Sydney, NSW. Most importantly, all costs are in AUD and include GST.
Smaller extensions often cost more than expected
For small extensions that do not include a kitchen or bathroom, the figures in the table above can be misleading. Smaller extensions tend to be disproportionately expensive because many fixed costs remain the same. This includes, for example, the costs for building approvals, site setup, tradespeople and compliance requirements. As a result, even a modest extension of around 10 square metres typically requires a minimum budget of approximately $80,000 when all necessary works are properly accounted for.
Ground Floor Extension Cost
For a brick-veneer ground floor extension, costs range from $2,600 to $3,200 per m². Above all, this depends on factors like:
- Foundation requirements
- Size (smaller extensions have a higher cost per m² – see above)
- Site access and terrain (sloping or flat)
- Building materials
Extension Cost for Adding a Second Storey
If expanding outward isn’t an option, consider building up. However, adding a second storey typically is more expensive, ranging from $4,000 to $4,500 per m². Reasons include:
- Replacing the roof and constructing a new one
- Reinforcing the ground floor walls to bear additional weight
- Installing a staircase
Additional Costs to Consider
Add cost for a new kitchen
Adding a standard, good-quality kitchen will cost $50,000 to $85,000 for cabinetry and benchtops. Appliances such as ovens, cooktops and dishwashers are extra. That said, luxurious finishes can quickly push the price for a new kitchen above $110,000.
Add cost for new bathrooms
Bathrooms are complex and expensive to build or renovate, costing about $35,000 to $50,000 each. In fact, most of the expense comes from labour (tiling, waterproofing, plumbing), with a smaller portion allocated to materials such as tiles, vanities, and tapware.
Cost Examples
Here’s what you might expect for your house extension cost in Sydney for common scenarios:
Ground Floor Extension (120m², with 1 bathroom and 1 kitchen):
- Total Cost: $397,000 to $519,000
Second Storey Addition (120m², with 2 bathrooms):
- Total Cost: $550,000 to $640,000
Inclusions in the Costs
Both vertical and horizontal extensions typically include:
- Demolition and excavation
- Timber framing, bricks and roofing
- Windows, doors and flooring
- Plumbing and electrical work
- Kitchen and bathrooms
- Insulation
Additionally, the costs assume a quality builder who is a member of either the Housing Industry Association (HIA) or the Master Builders Association (MBA). Not only do these memberships indicate proven expertise, but they also demonstrate ongoing professional development.
Other Expenses to Budget For Your Home Extension
Design and Approvals
Include fees for building designers, interior designers, surveyors, engineers and council approvals. Allow for $40,000 to $90,000. Learn more about fees for interior designers and what they typically include in this article.
Incorporate Insurance into Your House Extension Cost in Sydney
The Home Building Compensation Fund (HBCF) premium ranges from $3,000 to $6,000 for ground-floor projects, offering a safety net if your builder becomes insolvent.
Contingency Planning for Your House Extension Cost
Always set aside a contingency budget of approximately 20% to your house extension cost in Sydney. The reason is to cover unforeseen expenses, as renovating existing structures often reveals surprises that require additional work.
Return on Investment of your House Extension Cost
While extending your home requires a significant investment, Sydney’s property market offers strong potential for a high return. After all, a well-planned, quality extension can enhance your home’s value while giving your family the space and comfort they deserve. Don’t overlook the finishing touches that boost street appeal – stylish details like quality house numbers from Peninsula House Numbers can make a surprisingly strong first impression on visitors and potential buyers alike.
But the true value lies in the joy of creating a home that fits your lifestyle. After all, you can’t put a price on your family’s happiness.
This guide was collated by Martina Hayes, Interior and Building Design, who specialises in comprehensive home renovations.