How Much Does It Cost to Build a Duplex in Sydney?
A duplex development in Sydney costs $800,000 to $1,600,000+ for construction depending on size, spec level, and site conditions. That figure covers both dwellings — two complete homes on a single lot — from slab to handover. Based on Rawlinson Australian Construction Handbook data adjusted for 2026 Sydney market conditions, and Buildana's (Lic. 487805C) experience building duplexes across Fairfield, Liverpool, Cumberland and Canterbury-Bankstown, here is what you should budget.
Construction Cost per sqm — Duplex 2026
Rawlinson classifies duplexes under 'townhouses/villas' construction rates. Adjusted for 2026 Sydney:
• Medium standard, brick veneer: $2,195–$2,370/sqm • Medium standard, full brick: $2,280–$2,455/sqm • High standard, brick veneer: $3,075–$3,315/sqm • High standard, full brick: $3,130–$3,375/sqm
These rates apply per square metre of total building area across both dwellings. For a typical duplex of 2 × 150 sqm = 300 sqm total at medium brick veneer:
Construction: 300 × $2,195–$2,370 = $658,500–$711,000
For a larger duplex of 2 × 200 sqm = 400 sqm total at medium full brick:
Construction: 400 × $2,280–$2,455 = $912,000–$982,000
These are construction-only costs. Add demolition, site works, external works, and council fees for the total project cost.
Total All-In Duplex Costs — Western Sydney 2026
Total project cost including demolition, construction, external works, and council fees:
• Standard duplex (2 × 120 sqm), medium brick veneer: $650,000–$750,000 • Quality duplex (2 × 150 sqm), medium full brick: $850,000–$980,000 • Large duplex (2 × 200 sqm), high brick veneer: $1,200,000–$1,400,000 • Prestige duplex (2 × 220 sqm+), high full brick: $1,400,000–$1,600,000+
These figures include: • Demolition of existing dwelling: $10,000–$20,000 • Asbestos removal: $5,000–$25,000 • Geotechnical and survey: $5,000–$8,000 • Construction of both dwellings • Basic external works per dwelling (driveway, landscaping, fencing): $30,000–$60,000 per dwelling • Council contributions: $30,000–$60,000 (varies by council — Liverpool City Council charges significantly more than Fairfield City Council) • CDC or DA approval: $5,000–$15,000
Buildana builds most duplexes in Western Sydney in the $850,000–$1,200,000 range — quality 3–4 bedroom homes with double garages, modern kitchens, and good finishes.
What Affects Duplex Construction Cost Most
Five cost drivers create the biggest variation between duplex projects:
1. Dwelling size. Each additional sqm adds $2,195–$3,375 per sqm depending on spec. Going from 2 × 120 sqm to 2 × 180 sqm adds $260,000–$400,000.
2. Configuration — attached vs detached. Attached duplexes share a party wall, reducing external wall cost by approximately 10–15 per cent compared to detached. However, detached duplexes provide better acoustic separation and may attract higher rents or sale prices.
3. Spec level. The jump from medium to high spec adds approximately $880–$945/sqm. On a 300 sqm total duplex, that is $264,000–$283,500.
4. Site conditions. Reactive clay (common in Western Sydney) requires engineered foundations — $10,000–$30,000 extra per dwelling. Sloping blocks require retaining walls. Rock adds excavation costs.
5. Torrens title subdivision. If you want to sell the dwellings separately, you need Torrens title subdivision — a legal process that costs $30,000–$60,000 including surveyor, solicitor, council contributions, and Sydney Water compliance. This is in addition to construction cost.
For the complete duplex building process, see our comprehensive guide to building a duplex in Sydney.
Get a Fixed-Price Duplex Quote
Buildana provides fixed-price contracts for duplex development. Our quote covers demolition, construction of both dwellings, external works, and all approval fees. No provisional sums, no cost-plus surprises.
We start with a free site assessment — checking your block's zoning, FSR, setbacks, soil type, and duplex feasibility. If your block qualifies, you receive a detailed scope and pricing proposal before committing.
Contact Buildana for a free duplex feasibility assessment.
