How Much Does a Home Extension Cost in Sydney?

Home extension costs in Sydney range from $120,000 to $350,000+ depending on size, type, and complexity. This guide breaks down costs for every type of home extension — ground-floor additions, rear extensions, side extensions, and room-over-garage conversions — so you can plan your budget with confidence.

The cost per square metre for home extensions in Sydney ranges from $2,500/sqm for basic additions to $4,500/sqm for premium extensions with high-end finishes. Extensions typically cost more per square metre than new builds because integrating new construction with existing structures requires careful structural engineering, matching of materials, and weatherproofing at the junction.

Ground-Floor Extension Costs

Ground-floor extensions are the most common type of home addition. Typical costs:

• Small extension (20–30sqm): $80,000 – $150,000 • Medium extension (30–50sqm): $150,000 – $250,000 • Large extension (50–70sqm): $250,000 – $350,000+

Ground-floor extensions work well for adding bedrooms, family rooms, rumpus rooms, or expanding living areas. They require new footings and slab, integration with the existing roofline, and careful management of the junction between old and new construction.

Key cost factors include: • Soil conditions and footing requirements • Roof integration complexity — extending the existing roofline vs a separate roof structure • Number of wet areas (bathrooms, laundry) • Level of finishes — basic vs premium • Structural modifications to existing walls

Rear Addition Costs (Open-Plan Kitchen/Living)

Rear additions that open up the back of the house into a modern kitchen, dining, and living area are extremely popular across Western Sydney. Costs range from $150,000 to $300,000.

A typical rear addition involves: • Removing the existing rear wall (load-bearing wall removal with steel beam: $8,000 – $15,000) • New slab and footings for the extension • Open-plan kitchen with stone benchtops and custom cabinetry: $35,000 – $65,000 • Dining and living area with feature tiling or timber flooring • Large sliding doors or bi-fold doors opening to outdoor area: $6,000 – $15,000 • New roofline integration • BASIX compliance — insulation, glazing, water efficiency

Rear additions deliver the highest lifestyle improvement of any extension type and typically add 15–25% to property value.

Do You Need Council Approval for an Extension?

Yes — most home extensions require council approval. The two pathways are:

**Development Application (DA):** • Lodged with your local council (Fairfield, Liverpool, Cumberland, Canterbury-Bankstown, or Blacktown) • Processing time: 40–90 days • Required for extensions that don't meet CDC criteria • Council assesses impact on neighbours, overshadowing, privacy, streetscape

**Complying Development Certificate (CDC):** • Assessed by an accredited certifier (not council) • Processing time: 10–20 business days • Available for extensions that meet specific criteria under the NSW Housing SEPP • Generally faster and cheaper than DA

Buildana manages the entire approval process for home extensions across all five Western Sydney LGAs. We assess which pathway is fastest for your specific project and handle all documentation, plans, BASIX certificates, and engineering requirements.

Call 0476 300 300 for a free site assessment and extension quotation.

Extension vs Knockdown Rebuild: Which Is Better?

If your extension budget is approaching $300,000+, it's worth comparing the cost against a full knockdown rebuild. Here's the decision framework:

**Choose extension if:** • The existing structure is sound (good foundations, no major cracking, no termite damage) • You need less than 50% additional floor area • Budget is under $250,000 • The existing layout is mostly functional • You want to retain character features or heritage elements

**Choose knockdown rebuild if:** • The existing structure needs significant remediation • You want to completely change the layout • You need more than 50% additional floor area • The existing home has asbestos throughout • The cost of extension + existing home renovation exceeds 60% of a new build cost

Buildana can assess both options and provide cost comparisons. In many Western Sydney suburbs, the decision comes down to the condition of the existing foundations and whether they can support an extension or second storey.

Buildana builds across Sydney. Visit /advisory/value-engineering to learn more or /contact to discuss your project.