by: Martina Hayes
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 might be the better option. 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
Use the table below as a guide. Start by deciding whether to expand outwards or upwards, then calculate the area you wish to extend. If you’re adding a kitchen or bathroom, include those costs too.
| Price per additional square metre | Add for kitchen | Add for each bathroom | |
| Ground floor extension | $2,400 – $2,900 | $45,000 – $80,000 | $35,000 – $50,000 |
| First floor addition | $3,800 – $4,200 | $45,000 – $80,000 | $35,000 – $50,000 |
This information is to be used as a guide only. The prices apply to Sydney NSW. All costs include GST.
Ground Floor Extension
For a brick veneer ground floor extension, costs range from $2,400 to $2,900 per m², depending on factors like:
- Foundation requirements
- Size (smaller extensions have a higher cost per m²)
- Site access and terrain (sloping or flat)
- Building materials
Adding a Second Storey
If expanding outward isn’t an option, consider building up. However, adding a second storey typically costs more, ranging from $3,800 to $4,200 per m². Reasons include:
- Replacing the roof and constructing a new one
- Reinforcing ground floor walls to bear additional weight
- Installing a staircase
Additional Costs to Consider
Add cost for new kitchen
Adding a standard, good-quality kitchen will cost $45,000 to $80,000 for cabinetry and benchtops. Appliances such as ovens, cooktops, and dishwashers are extra. Luxurious finishes can easily push costs beyond $110,000.
Bathroom
Bathrooms are labour-intensive, costing $35,000 to $50,000 each. Most of the expense comes from labour (tiling, waterproofing, plumbing), with a smaller portion for materials like tiles, vanities and shower screens.
Cost Examples
Here’s what you might expect to pay for common scenarios:
Ground Floor Extension (120m², with 1 bathroom and 1 kitchen):
- Total Cost: $368,000 to $478,000
Second Storey Addition (120m², with 2 bathrooms):
- Total Cost: $536,000 to $604,000
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
- 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). These memberships indicate proven expertise and ongoing professional development.
Other Expenses to Budget for
- Design and Approvals: Include fees for architects, surveyors, engineers, and council approvals. Allow for $40,000 to $90,000.
- Insurance: 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
Always set aside a contingency budget of approx. 20% of your construction cost to cover unforeseen expenses. Renovating existing structures often reveals surprises that require extra work.
Return on Investment
While extending your home requires a significant investment, Sydney’s property market offers strong potential for a high return. A well-planned, quality extension can enhance your home’s value while giving your family the space and comfort they deserve.
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 family happiness!
This guide was collated by Martina Hayes, Interior and Building Design, who specialises in comprehensive home renovations.