How Much Does a Home Extension Cost in Sydney?

Home extensions in Sydney cost $150,000 to $600,000+ depending on whether you extend the ground floor or add a second storey addition, and the level of finish. Ground floor extensions run $3,500 to $6,000 per m². Second storey additions cost $4,500 to $7,000 per m².

At Dura Group, we’ve been building professional home extensions across the Sutherland Shire for over 25 years. This guide gives you realistic cost ranges based on what we quote and deliver on actual projects.

Home Extension Costs in Sydney (2026)

extension and addition services: $150,000 to $400,000+

A ground floor extension pushes the footprint of your home outward, typically at the rear. Costs depend on the size and complexity: (see our renovating in the Sutherland Shire)

• Small extension (15 to 25m²): $150,000 to $200,000. A single room addition like a family room, rumpus room, or expanded kitchen/dining area
• Medium extension (25 to 40m²): $200,000 to $300,000. Typically a new open-plan kitchen, dining, and living area with bi-fold doors to the backyard
• Large extension (40m²+): $300,000 to $400,000+. A major addition that might include a new kitchen, living area, bathroom, and laundry

Ground floor extensions are generally less expensive per square metre than going up because they don’t require structural reinforcement of the existing home. Our ground floor extension guide covers the full process, costs, and what to expect.

house extensions: $250,000 to $600,000+

A second storey addition adds living space without sacrificing backyard area. It’s a bigger project with more structural requirements:

• Partial second storey (30 to 50m²): $250,000 to $350,000. Adds 2 to 3 bedrooms and a bathroom above the existing ground floor
• Full second storey (60 to 100m²): $350,000 to $600,000+. A complete upper level with multiple bedrooms, bathroom, living area, and potentially a balcony

Second storey additions cost more because the existing ground floor structure often needs reinforcing, new footings may be required, and the roof needs to be removed and rebuilt. You’ll also need scaffolding for the duration of the build.

What Drives Home Extension Costs?

Structural Engineering

Every extension needs structural engineering. For ground floor work, this covers new footings, slab design, and connections to the existing structure. For second storey additions, you’ll also need assessment of whether the existing walls and footings can carry the additional load. Engineering fees run $3,000 to $10,000 depending on complexity.

Council Approvals

Most extensions require either a DA (Development Application) or CDC (Complying Development Certificate). We handle the entire approval process for you, including architectural drawings, engineering, BASIX certificates, and council liaison. Approval costs range from $3,000 to $15,000.

Site Conditions

The Sutherland Shire has its share of challenging sites. Sloping blocks, rock, and limited access all affect cost. Excavation on a rocky site can add $10,000 to $30,000. Properties on steep blocks near bushland may also need retaining walls and BAL (Bushfire Attack Level) compliant construction.

Finishes and Fit-Out

The shell of an extension (structure, roof, walls, windows) accounts for roughly 60% of the cost. The remaining 40% is internal fit-out: flooring, kitchen, bathroom, painting, lighting, and cabinetry. This is where you have the most control over budget.

At Dura Group, you choose and purchase your own finishes. We don’t add markups on materials or fixtures, so your fit-out budget goes further.

Extension Cost Per Square Metre

As a rough guide for Sydney in 2026:

• Ground floor extension: $3,500 to $6,000 per m²
• Second storey addition: $4,500 to $7,000 per m²

These figures include everything: structural work, approvals, full fit-out, and project management. The wide range reflects differences in site conditions, finishes, and complexity. See our Sydney building costs guide for current rates across all project types.

Extension vs Renovation vs Moving

The right choice depends on your situation:

• Extend if you love your location and your existing home has good bones but not enough space
• Renovate if the space is adequate but the layout, finishes, or functionality need updating (see our renovate or rebuild comparison)
• Move if the cost of extending exceeds the value it adds to your home, or if the block has limitations that make extending impractical

Across the Sutherland Shire, the cost of stamp duty alone on buying a new property ($30,000 to $60,000+) makes extending a more financially sensible option.

Home Extension Timeline

• Design and approvals: 8 to 16 weeks (depends on DA vs CDC pathway)
• Ground floor extension build: 12 to 20 weeks
• Second storey addition build: 16 to 30 weeks

Understanding the building process helps you plan your timeline and set expectations.

Why Dura Group for Your Home Extension

• Fixed-price contracts so you know the full cost before we start
• All approvals handled from DA/CDC through to occupation certificate
• No material markups on finishes and fixtures
• 25+ years experience building extensions across the Sutherland Shire
• Mark manages every project directly

Browse our home extension gallery to see recent work, or explore extensions we’ve built in Sutherland Shire house additions, Cronulla house additions, Menai home extensions, Jannali house additions, and Illawong home extensions.

Get a Quote for Your Home Extension

Every extension project is different. The best way to get an accurate cost is to have us visit your property, understand what you want, and assess the site. We’ll give you a realistic number, not a vague estimate.

Contact Dura Group today or call Mark on 0424 665 793.

Frequently Asked Questions

How much does a ground floor extension cost in Sydney?

A ground floor extension in Sydney costs $150,000 to $400,000+ depending on size, site conditions, and level of finish. Expect to pay $3,500 to $6,000 per square metre fully fitted out.

How much does a second storey addition cost?

A second storey addition in Sydney costs $250,000 to $600,000+. The higher cost reflects structural reinforcement of the existing home, roof removal and rebuild, and scaffolding.

Do I need council approval for a home extension?

Yes. Most extensions require either a DA or CDC. We handle the entire approval process for you, including engineering, architectural drawings, and BASIX certification.

How long does a home extension take to build?

A ground floor extension takes 12 to 20 weeks to build. A second storey addition takes 16 to 30 weeks. Add 8 to 16 weeks for design and approvals before construction starts.

Is it cheaper to extend or move house?

In most cases, extending is cheaper when you factor in stamp duty, agent fees, moving costs, and the premium paid on a larger home. In the Sutherland Shire, stamp duty alone can be $30,000 to $60,000+.