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NSW Dual Occupancy Development Calculator (2026)

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Dual Occupancy Development Feasibility in NSW

Dual occupancy developments — building two dwellings on a single residential lot — have become one of the most popular property development strategies in New South Wales. Whether you're considering an attached duplex or a primary dwelling with a detached granny flat, understanding the financial feasibility is critical before committing capital.

Key Cost Components

Acquisition Costs

This includes the land purchase price, stamp duty (use our NSW Stamp Duty Calculator to estimate), legal fees, and conveyancing costs. In Sydney's metropolitan areas, land typically represents 50-70% of total project costs.

Construction Costs

Construction costs for dual occupancy in NSW typically range from $2,000 to $3,500 per square metre depending on the specification level, site conditions, and builder. Budget for demolition (if applicable), DA and certification fees, construction, landscaping, driveways, and external works. A contingency of 10-15% is standard practice.

Holding Costs

Holding costs include loan interest, council rates, land tax, and insurance during the development period. A typical dual occupancy takes 12-18 months from purchase to sale. These costs are often underestimated and can significantly erode profit margins.

Selling Costs

Agent commissions in NSW typically range from 1.5% to 2.5% of the sale price. Marketing costs (photography, signage, online listings, styling) can add $5,000-$15,000 per dwelling.

Understanding the Results

Profit Margin measures gross profit as a percentage of total costs. Most lenders and experienced developers consider 15-20% a minimum viable margin for small-scale residential development.

ROI (Cash-on-Cash Return) measures the profit relative to the actual cash you invested (excluding borrowed funds). This metric is particularly useful when comparing leveraged development returns to other investment options.

Disclaimer: This calculator provides estimates for preliminary feasibility assessment. Actual costs and returns vary significantly based on location, market conditions, builder selection, and project management. Engage a qualified quantity surveyor, accountant, and solicitor before committing to a development.

Frequently Asked Questions

What is a dual occupancy development?
A dual occupancy is a development where two dwellings are built on a single lot. This can be an attached duplex (two dwellings sharing a common wall) or a detached dual occupancy (a primary dwelling and a secondary dwelling like a granny flat). In NSW, dual occupancy is a popular strategy for maximising land value.
What is a good profit margin for a dual occupancy project?
Most developers target a minimum profit margin of 15-20% on total development cost. A margin below 10% is generally considered too risky once you account for contingencies, market fluctuations, and potential cost overruns. This calculator helps you assess whether your project meets these thresholds.
What are the minimum lot sizes for dual occupancy in NSW?
Minimum lot sizes vary by local council (LGA). In many Sydney metropolitan councils, the minimum lot size for a dual occupancy ranges from 450m² to 600m² depending on the zoning (R2, R3, etc.). Always check your local council's Development Control Plan (DCP) for specific requirements.
Do I need council approval for a dual occupancy in NSW?
Yes. Dual occupancy developments in NSW require Development Application (DA) approval from your local council, or in some cases a Complying Development Certificate (CDC) if the development meets specific criteria under the State Environmental Planning Policy (Exempt and Complying Development Codes).
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