For Northern Beaches homeowners who want more from their block of land, building a duplex can open the door to everything from multi-generational living to an additional property or future subdivision.
Moving can often mean giving up the suburb, street or lifestyle you already love. A duplex offers another way forward: making better use of the land you already own, while staying put and creating more flexibility for how you live now and in the future.
Planning reforms recently introduced also encourages duplexes; dual occupancies and semi-detached dwellings are now permitted in R2 Low Density zones with development consent on the Northern Beaches (and beyond).
So if you’ve ever wondered whether your existing block might have that kind of potential, G.J. Gardner’s free 90-minute masterclass in Brookvale can help you get started.
Local builders Anthony and Tony Raco will host a series of Northern Beaches Duplex Masterclass in September, giving homeowners the chance to explore what could work on their own block.
The session will walk through the process from early site feasibility and design choices to approvals, construction and subdivision, followed by an interactive Q&A and time for one-on-one project discussions.
For Anthony and Tony, it starts with a fairly simple question: could a duplex work on your block, and what would it take to make the project stack up?
Anthony and Tony opened the G.J. Gardner Homes Northern Beaches franchise in Brookvale in February this year, bringing more than two decades of residential building experience, primarily on the Northern Beaches.
The family-run business operates from a studio at 517 Pittwater Road and works with homeowners from Manly to Palm Beach on duplexes, knockdown rebuilds, major renovations and custom homes.
Building a duplex on the Northern Beaches
No two blocks are quite the same, particularly on the Northern Beaches. Lot width, zoning, slope, drainage, sandstone and even a property’s orientation can shape what homeowners can do with their land.
The masterclass is designed to make those considerations easier to understand before anyone gets too far down the track.
“When local families come to us wanting to build a duplex, they’re usually surprised by what happens before the slab is even poured,” said Tony Raco, Managing Director of G.J. Gardner Homes Northern Beaches.
“It’s easy to focus on the build quote, but you have to factor in council zoning limits, strict frontage minimums, and the legalities of title separation and subdivision fees.”
Knowing about those details early doesn’t necessarily make them roadblocks. Tony says it can help homeowners make smarter choices about the design and long-term value of both homes.
“If you don’t account for how the slope and orientation affect each side, you can easily end up with unequal valuations between the two residences,” he said.
“Understanding those hyper-local nuances upfront is what turns a good idea into a genuinely successful project.”
The masterclass will also explain the different approval pathways available for a duplex, including Development Applications and Complying Development Certificates, as well as the differences between Torrens and strata subdivision.
What About Cost and Timing?
Of course, one of the biggest questions for anyone considering a duplex is whether the numbers add up.
Anthony and Tony will also break down the financial side of the process, including the factors that can push a duplex construction budget up or down.
G.J. Gardner Homes Northern Beaches says a duplex build typically ranges from $1.2 million to $1.7 million, depending on the project scope and site engineering. The figure covers a duplex with two dwellings and is based on the builder’s Standard Inclusions package, including site costs and reports.
The team says fixed pricing is set once its Authority To Proceed reports are complete and is based on those Standard Inclusions. Clients who later decide to upgrade beyond the standard package can incur variations.
How long a build takes can depend on size and complexity, with G.J. Gardner saying projects are usually completed within about 12 months of construction commencing.
The Northern Beaches Duplex Masterclass will be held at G.J. Gardner Homes Northern Beaches, 517 Pittwater Road, Brookvale, on Thursday 24 September 2026 from 6pm to 7.30pm. Doors open at 5.45pm for drinks and light refreshments, with the presentation beginning at 6pm, followed by a Q&A and one-on-one project discussions.
Admission is free, but places are limited and require registration. Pre-register to secure your spot and find out whether your Northern Beaches block could support a duplex.
