Home Extension Cost Perth 2026: Build Up vs Build Out — What Perth Builders Charge
Home extensions in Perth are one of the most complex renovation projects, involving structural engineering, council approval, and coordination of multiple licensed trades. This guide covers real 2026 pricing for single-storey and double-storey extensions in Perth, WA.
Perth Home Extension Costs at a Glance (2026)
Perth uses a 1.18× regional multiplier. Extension costs are quoted per square metre of new floor area and include all trades, materials, council fees, and GST. Structural engineering and design fees are typically additional.
| Type | Perth Rate | Notes |
|---|---|---|
| Single-storey (basic) | $2,200 – $3,000/m² | New room, standard finishes, no wet areas |
| Single-storey (mid) | $3,000 – $4,200/m² | New room + wet area, quality finishes |
| Single-storey (premium) | $4,200 – $6,000/m² | High-spec finishes, complex design |
| Double-storey addition | $3,500 – $5,500/m² | Structural complexity, staircase, higher trades costs |
| Full second storey | $180,000 – $350,000+ | Full second storey — depends on existing structure |
Use our free renovation cost calculator to get a personalised estimate for your extension project.
WA Council Approval and Home Indemnity Insurance
All home extensions in Perth require a building permit from your local council. The permit process involves submitting plans prepared by a registered draftsperson or architect, structural engineering certification, and council assessment. Extensions in heritage areas or near boundaries require additional approvals. Your builder must be registered under the Building Services (Registration) Act 2011.
Home Indemnity Insurance (HII) is mandatory in Western Australia for residential building work over $20,000. It protects homeowners if the builder fails to complete the work or becomes insolvent. Your builder must arrange HII before commencing work. Do not pay a deposit without seeing the HII certificate. Verify your builder's registration at buildingcommission.wa.gov.au.
Build Up vs Build Out in Perth
Perth's predominantly single-storey housing stock means that many homeowners face a genuine choice between building out (extending the footprint) or building up (adding a second storey). Building out is generally less expensive per square metre but requires available land and may affect outdoor living areas. Building up preserves the backyard but involves higher structural costs and requires assessment of the existing slab and footings. Our build up vs build out guide covers this decision in detail.
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Frequently Asked Questions
How much does a home extension cost in Perth in 2026?
A standard 30m² single-storey addition in Perth costs approximately $80,000–$120,000. A premium 50m² addition costs $200,000–$300,000. A full second storey addition costs $200,000–$380,000 depending on the existing structure and design complexity.
What is Home Indemnity Insurance in WA?
Home Indemnity Insurance (HII) is mandatory in WA for residential building work over $20,000. It protects homeowners if the builder fails to complete the work or becomes insolvent. Your builder must arrange HII before commencing work.
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We update our data quarterly. Get notified when Perth rates change.