Cost Guide
Home Extension Costs in Australia
Comprehensive cost guide for all types of home extensions. Rates based on current Australian market data from 200+ licensed builders.
Extension Cost by Type
Rear Extension
30–40m² ground floor extension into backyard
Rate per m²
$2,500 – $4,000/m²
Typical Project
$80,000 – $160,000
Single Storey Extension
Any ground floor addition to the home footprint
Rate per m²
$2,500 – $4,500/m²
Typical Project
$100,000 – $200,000
Double Storey Extension
Full two-storey addition, includes structural work
Rate per m²
$3,000 – $5,000/m²
Typical Project
$200,000 – $450,000
Side Return Extension
Fills side passage, typically adds to kitchen
Rate per m²
$2,800 – $4,500/m²
Typical Project
$80,000 – $150,000
Kitchen & Living Extension
Open-plan kitchen/living, includes cabinetry
Rate per m²
$2,800 – $5,000/m²
Typical Project
$120,000 – $300,000
Bedroom Extension
Single bedroom through to full master suite
Rate per m²
$2,500 – $4,000/m²
Typical Project
$45,000 – $180,000
What Drives Extension Costs?
Size: Larger extensions have lower cost per m² due to economies of scale on fixed costs like scaffolding and amenities.
Structural complexity: Removing load-bearing walls, adding structural steel, or building on difficult sites adds 10–20% to costs.
Finishes & specification: Kitchen and bathroom fit-outs vary enormously — from $15,000 to $80,000+ for the same footprint.
Council approval type: CDC (fast track) approvals save time and money versus a full DA process which can add $10,000–$25,000.
Site access: Difficult access, steep blocks, or tight side clearances can add 10–15% to costs.
Location: Sydney and Melbourne typically run 10–15% above Brisbane, Adelaide, and Perth for equivalent work.
Note: These rates cover construction costs only. Council fees ($5k–$20k), architectural design ($8k–$25k), engineering ($2k–$8k), and landscaping are additional. Always request a fixed-price contract that covers all inclusions.