If you are thinking about extending your home, the first question is almost always the same. How much will it cost? The answer depends on what you are building, where you live, and the level of finish you want. But there are clear price ranges you can use to plan your budget before you even talk to a builder.
This guide breaks down home extension costs in Sydney and the Macarthur region for 2026. We cover pricing per square metre, the factors that push costs up or down, and what to expect at each stage of the build.
What Does the Average Home Extension Cost Per Square Metre
Home extension pricing in Sydney typically falls into three tiers based on the quality of materials and finishes.
A budget extension with standard finishes, basic fixtures, and simple roofing generally sits between $1,800 and $2,500 per square metre. This suits straightforward single room additions where you are matching existing finishes without upgrading them.
A mid-range extension with good quality fixtures, tiled flooring, and upgraded windows usually costs between $2,500 and $3,800 per square metre. This is where most family extensions land. It covers things like extra bedrooms, larger living areas, and open plan conversions with solid materials.
A premium extension with high-end cabinetry, stone benchtops, custom joinery, and architectural design work can run from $3,800 to $5,500 or more per square metre. This range applies to projects with complex roof lines, large glass features, or structural changes like removing load-bearing walls.
These ranges cover the build itself. They do not include council fees, engineering reports, or site preparation costs, which we cover further down.
Common Extension Types and What They Cost
Not every extension is the same size or complexity. Here is what typical projects look like at a mid-range finish level in the Macarthur and South West Sydney area.
Single bedroom addition (12 to 16 sqm): A new bedroom added to the rear or side of the house generally costs between $35,000 and $55,000. This assumes standard wall framing, a window, basic electrical, and internal lining to match the existing home.
Living area extension (20 to 35 sqm): Extending the living room or adding a family room typically ranges from $55,000 to $120,000. Larger openings, bifold doors, and connections to outdoor areas push this toward the higher end.
Kitchen and living combination (30 to 50 sqm): Combining a kitchen renovation with a living area extension is one of the most popular projects for growing families. Expect to spend between $90,000 and $180,000 depending on the kitchen fit-out and the amount of structural work needed.
Full rear extension (40 to 60 sqm): A large rear extension that adds multiple rooms or creates a new open plan living, dining, and kitchen space generally costs between $120,000 and $220,000 at a mid-range finish.
Second storey addition (60 to 100 sqm): Going up is a bigger project. A full second storey with bedrooms, a bathroom, and a hallway typically ranges from $200,000 to $450,000. The wide range reflects differences in structural reinforcement, stair design, and the complexity of connecting the new level to the existing home.
What Drives the Cost Up
Several factors can push an extension well above the base per-square-metre rate. Knowing these in advance helps you budget more accurately.
Structural work is the biggest variable. If your extension requires removing load-bearing walls, underpinning existing foundations, or reinforcing the roof, the engineering and labour costs add up quickly. A structural engineer’s report alone can cost $1,500 to $4,000.
Site access matters more than most people expect. If your block has narrow side access, steep slopes, or retaining walls in the way, the cost of getting materials and machinery on site increases. Tight access in suburbs like Campbelltown and older parts of Camden can add 5 to 15 percent to the build cost.
Wet areas are expensive per square metre. Any room with plumbing, tiling, and waterproofing, like a bathroom, laundry, or kitchen, costs more to build than a standard bedroom or living area. Bathroom additions within an extension can add $25,000 to $50,000 to the total depending on size and finishes.
Council and compliance costs include development application fees, building certification, and any required reports like bushfire assessments, flood studies, or BASIX certificates. These can range from $3,000 to $12,000 depending on your local council area and the scale of the project.
Finishes and fixtures are where budgets blow out most often. Upgrading from laminate to stone benchtops, choosing custom joinery over flat-pack, or specifying imported tiles versus local options can shift the total cost by tens of thousands of dollars.
What Drives the Cost Down
There are practical ways to keep an extension affordable without cutting quality.
Simple rooflines save money. A flat or skillion roof extension is cheaper to build than one that matches a complex hip or gable roof on the existing house. If your home suits a modern flat roof addition, the savings on framing and roofing can be significant.
Staying on one level avoids the major costs of structural reinforcement, stairs, and balustrades that come with a second storey. If your block has enough space, building outward is almost always cheaper than building up.
Keeping wet areas close to existing plumbing reduces the length and complexity of pipe runs. Adding a bathroom directly behind an existing wet wall is cheaper than running new plumbing to the far side of the house.
Choosing standard sizes for windows, doors, and openings keeps costs down because they can be sourced off the shelf. Custom sizes require special orders and longer lead times.
The Costs Most People Forget
Beyond the build itself, there are several line items that catch homeowners off guard.
Temporary accommodation: Depending on the size and location of the extension, you may need to move out for part of the build. Budget for short-term rental if the project affects your kitchen or bathrooms.
Landscaping reinstatement: Extensions often require digging up part of the yard, removing fences, or cutting into driveways. Rebuilding these after the build is a separate cost, usually $3,000 to $10,000.
Service relocations: If your extension runs over existing gas lines, stormwater drains, or electrical conduits, these need to be moved before construction starts. Utility relocation can cost $2,000 to $8,000.
Interior finishing of existing rooms: Where the new extension meets the old house, you will usually need to patch, repaint, and sometimes re-floor the connection zone. This is often left out of initial quotes.
How to Get an Accurate Quote
The most reliable way to understand your extension cost is to get a detailed, itemised quote from a licensed builder who inspects your property in person. Online calculators give you a rough idea, but they cannot account for your block’s slope, soil type, access, or the structural condition of your existing home.
When comparing quotes, make sure each one covers the same scope. A lower price might exclude council fees, engineering, or site preparation that another builder has included. Ask what is and is not covered before comparing numbers.
Ready to Plan Your Extension
Token Building has been delivering home extensions across the Macarthur and South West Sydney region for over 20 years. We provide free consultations with transparent, itemised quotes so you know exactly what your project will cost before any work begins.
Get in touch today to discuss your extension plans.