What Block Size Do You Need for a Duplex in NSW?
The minimum block size for a duplex in NSW is set by your local council's LEP (Local Environmental Plan). It varies by council and zone. Buildana (Lic. 487805C) has built duplexes on blocks from 450 sqm to 800+ sqm across Western Sydney. Here are the requirements and what each block size allows.
Minimum Lot Size by Council
Minimum lot sizes for dual occupancy (duplex) in Western Sydney councils (2026):
• Fairfield City Council: 450 sqm (R2), varies (R3) • Liverpool City Council: 500 sqm (R2) • Canterbury-Bankstown City Council: 460 sqm (R2) • Cumberland Council: 450 sqm (R2) • Blacktown City Council: 450–500 sqm (R2)
Note: These are minimum lot sizes for the parent lot before subdivision. If you want Torrens title subdivision, each resulting lot must also meet the minimum lot size per dwelling — typically 225–300 sqm per lot.
Minimum frontage requirements: • Fairfield: 12m (14m for detached duplex) • Liverpool: 15m • Canterbury-Bankstown: 12m • Cumberland: 12m • Blacktown: 12m
Frontage is often the more restrictive requirement. Many blocks in older Western Sydney suburbs have 12–13m frontage, which qualifies everywhere except Liverpool (15m minimum).
What You Can Build by Block Size
450–500 sqm block (FSR 0.5:1): • Maximum floor area: 225–250 sqm total (both dwellings) • Typical configuration: 2 × 110–125 sqm (3-bed, 2-bath per dwelling) • Attached duplex only (detached rarely fits) • Single garage per dwelling (double may not fit) • Limited outdoor space — meets minimum requirements only
500–600 sqm block (FSR 0.5:1): • Maximum floor area: 250–300 sqm total • Typical configuration: 2 × 125–150 sqm (3–4 bed, 2-bath per dwelling) • Attached duplex with double garage per dwelling • Reasonable outdoor space per dwelling • This is the sweet spot for duplex development in Western Sydney
600–800 sqm block (FSR 0.5:1): • Maximum floor area: 300–400 sqm total • Typical configuration: 2 × 150–200 sqm (4-bed, 2–3 bath per dwelling) • Attached or detached duplex • Double garage per dwelling with potential for side access • Generous outdoor space
800+ sqm block: • Consider townhouse development (if R3 zoned) for higher returns • Duplex with very generous dwellings (2 × 200+ sqm) • Detached duplex with substantial courtyard areas
Checking Your Block's Suitability
Three quick checks before contacting a builder:
1. Check zoning — use the NSW Planning Portal (planningportal.nsw.gov.au). Enter your address and check the Land Zoning Map. Dual occupancy requires R2 or R3 (or equivalent under the new Standard Instrument zones).
2. Check lot size — your Certificate of Title shows the lot area. If under the council's minimum, a duplex is not permitted.
3. Check frontage — measure or check the deposited plan (lot survey). If under 12m (or 15m for Liverpool), duplex may not be feasible.
Buildana performs these checks as part of our free duplex feasibility assessment — plus soil assessment, flood mapping, heritage checks, and financial feasibility. Contact Buildana to book your assessment. For the full process, see our comprehensive guide to building a duplex in Sydney.
