List rooms, square metres, wet areas and whether the family will live in the home during work.
Home Extension Costs
Home extension cost in Australia
Short answer
A home extension is harder to estimate than a single-room renovation because structural work, approvals, access, engineering, services, roofing, windows, insulation and finish level all affect the quote. Use early estimates only to set a budget range before drawings and builder review.
Main cost drivers
- Ground floor extension versus second-storey addition.
- Engineering, foundations, roof changes and structural tie-ins.
- Kitchen, bathroom, laundry or wet-area inclusions.
- Windows, doors, insulation, cladding, roofing and flooring.
- Planning approvals, certifier, design, drawings and site constraints.
Prepare before contacting builders
Collect site plans, existing drawings, survey details and any council constraints.
Share a realistic range and ask what is excluded, provisional or subject to engineering.
Builder Brief
Prepare a home extension quote brief
A clearer scope helps builders respond with fewer assumptions and more comparable quotes.
General planning information only. Confirm site-specific pricing with designers, certifiers and licensed builders.