As Sydney’s property market continues to evolve, the duplex has become one of the smartest and most versatile ways to maximise your land’s potential.

Whether you’re developing for profit, creating dual living for family, or building a high-end residence that delivers two stunning homes on one block, the financial and lifestyle rewards can be remarkable.

At Phase Projects, we’ve delivered duplexes that define both ends of the spectrum, from luxury coastal builds like Arncliffe and Bexley complete with pools and basement parking, to cost-effective investment builds such as our Revesby project.
Each is Duplex project we have completed is proof that success isn’t about spending more, it’s about designing smartly and building with precision.

Why Duplex Builds Are in Demand

In Sydney, land is at a premium. Building two homes on one block offers flexibility and return that traditional single dwellings simply can’t match. Duplexes suit a wide range of goals:

• Investors looking to build and sell both for profit.
• Owner-occupiers who live in one and rent the other.
• Families creating multi-generational homes that balance privacy and proximity.

The result? More living space, more value, and a stronger long-term asset.

The Cost to Build a Duplex in Sydney

The cost of building a duplex varies widely depending on design, inclusions, and site conditions, but here’s a realistic guide based on Sydney’s current market.

Type	Typical Build Cost (excluding land)	Description
Cost-Effective Duplex	From $700,000–$1.1 million	Ideal for investors or developers seeking strong ROI. Practical finishes, efficient layouts, and lower ongoing maintenance.
Luxury Duplex	From $1.3 million–$2.5 million+	Premium inclusions, architectural design, and often featuring pools, basements, or high-end finishes. Perfect for prestige buyers or long-term investors.

Luxury Duplex Builds: Living Without Compromise

In Sydney’s Eastern and St George regions, luxury duplexes are redefining what multi-dwelling living can look like.

At Arncliffe, Phase Projects created a basement-level garage with a car turntable, a full outdoor entertaining area, and private pools for each residence, blending functionality with prestige design.

At Bexley, we delivered dual homes with high-end stone finishes, seamless indoor–outdoor living, and sophisticated landscaping that enhances street appeal and resale value.

Each project proves that a duplex can be as luxurious and architecturally striking as a standalone custom home.

Investor-Focused Duplex Builds: Smart and Strategic

Not every project needs marble and Miele.
For investors, the goal is often maximising return per square metre. That’s where our Revesby project stands out, as a cost-effective duplex that maintained design integrity while delivering excellent rental and resale potential.

We help investors make informed choices about finishes, layouts, and inclusions that balance cost, quality, and long-term durability — ensuring every dollar contributes to measurable value.

Designing for Privacy and Comfort

Whether you’re building to live in or to lease, privacy is key.
Our duplex designs include:

• Acoustic separation between dwellings for noise reduction.
• Landscaping and window placement for visual privacy.
• Individual entries and outdoor zones that enhance independence and lifestyle.

This attention to detail ensures each home feels private, comfortable, and complete, whether occupied by family or tenants.

Council Approvals and Feasibility

Every Sydney council has its own rules on duplex development — from minimum lot widths to height limits and off-street parking requirements.
Phase Projects handles the entire process, including:

• Site feasibility and zoning checks.
• Development Applications (DA) or Complying Development Certificates (CDC).
• Coordination with engineers, surveyors, and private certifiers.

Our experience ensures that approval pathways are smooth and delays are minimised.

The Return on Investment

Done well, a duplex can deliver both capital growth and immediate rental yield.
Sydney’s high-demand suburbs, particularly in the St George, Inner West, and Eastern Suburbs , often see duplexes resell at a premium, thanks to their dual occupancy flexibility and modern appeal.

And because each build is custom-designed, you control the balance between lifestyle, luxury, and profit.

The Takeaway

Whether your goal is to create a luxury residence or a high-performing investment, a duplex is one of the most efficient ways to maximise land value in Sydney’s competitive market.

At Phase Projects, we combine design intelligence with construction expertise and deliver duplexes that are beautiful, functional, and built to perform.

Contact us today to discuss your block, your budget, and your goals. We’ll help you explore your options and show you how to make your duplex vision a reality.

FAQs — Duplex Build Cost Sydney

How much does it cost to build a duplex in Sydney?
Depending on design, finishes, and site conditions, expect between $700,000 and $2.5 million for the build alone. This excludes land, demolition, and approvals.

What affects duplex building costs the most?
Site slope, access, foundation type, materials, and level of finish are the main variables. Basements, pools, and premium inclusions increase costs but also add value.

Is it cheaper to build a duplex or two separate homes?
Building a duplex is generally more cost-effective, as you share land, some services, and certain construction elements between the two homes.

Can I build a duplex on any block in Sydney?
Not all blocks are suitable. Councils typically require minimum land size (around 400–500m²) and width (around 15m). We assess this as part of your site feasibility.

How long does it take to build a duplex?
Typically 12–18 months, depending on design complexity, weather, and approval timelines.

Do I need council approval for a duplex?
Yes. Duplexes usually require a Development Application (DA), but some may qualify for a Complying Development Certificate (CDC) if all planning conditions are met.

What’s the best strategy for investors building a duplex?
Define your goal early — sell both, sell one and retain one, or rent both. Your financial and design strategy should align with that outcome.

How can a duplex improve my property value?
A well-designed duplex can significantly increase land value, especially in high-demand suburbs. Dual income potential also boosts buyer and tenant appeal.

Can Phase Projects build luxury duplexes with basements and pools?
Absolutely. We specialise in high-end duplex construction, including basements, pools, and smart home integrations.

What’s the first step to start building a duplex in Sydney?
Contact Phase Projects for a consultation. We’ll assess your site, outline realistic costs, and help you plan a project that fits your financial and lifestyle goals.