Duplex design

Duplex design in Sydney
and coastal NSW.

Site-specific duplex design and approval management for homeowners, investors and developers turning one block into two homes.

Check what your block can do Talk to us
350+Residential approvals over 25+ years
99%Approval success rate
20+Councils across 5 states
Building Designers Association of AustraliaBDAA Accredited Building DesignerMember, Building Designers Association of Australia
In-houseTown planning, with the approval process managed for you
Who it's for

One block, two homes.

Homeowners

Unlock the potential of your property with a dual occupancy development. Whether you plan to live in one home and sell or rent the other, or retain both, we create designs that support your lifestyle goals while maximising resale and investment value.

Investors and small developers

Turn one lot into two titled dwellings. From initial feasibility and development strategy through to design and approval management, we help you unlock your site's potential. Our focus is on maximising yield, reducing approval risk and delivering homes with strong market appeal and long-term value.

Buyers assessing a site

Thinking of buying a block for a duplex? Before you commit, we'll help you understand what the site can realistically deliver, from development potential and planning constraints to dwelling yield and project viability.

Why KEEP

Experience you can build on.

  • A proven track record

    33 approved duplex and multi-dwelling projects, plus single and secondary dwellings, all under the KEEP banner, and hundreds more successful development projects over 25+ years in the industry.

  • Town planning in-house

    Brendan Williams brings over fourteen years in the NSW planning system and manages development applications through to consent.

  • The right approval pathway, early

    We work out at the start whether complying development or a development application suits your site, so the design is built around it.

  • Design that adds value

    Considered layouts, privacy between the two homes, natural light and street presence: the things buyers and tenants pay for.

  • Fixed fees

    A fixed-price feasibility to start, credited against your full design fee if you go ahead.

From first site visit to builder quotes, see how we work
Approval pathways

Complying development or a development application.

Complying development (CDC)

Where eligible, a Complying Development Certificate (CDC) can provide a faster alternative to the traditional Development Application process. We assess your site's suitability against the relevant State planning controls and development standards to determine whether a CDC pathway is achievable. If the proposal can satisfy the applicable requirements, approval can be obtained through a private certifier without the need for a Council Development Application.

By streamlining the approval process, a CDC can reduce project timeframes, allowing construction to commence sooner. For investors and developers, this can result in lower holding costs, reduced approval risk and improved project feasibility and profitability.

Development application (DA)

A Development Application (DA) is a merit-based assessment undertaken by Council and is typically required for sites or designs that do not meet the standards of the NSW Complying Development Codes. In many cases, the DA pathway can provide greater design flexibility and create opportunities to achieve improved planning and development outcomes.

Our in-house Town Planner, Brendan, assesses each project's planning constraints and opportunities, preparing and managing the application through to determination. By integrating planning and design expertise from the outset, we help reduce approval risk and maximise the potential of your site.

Duplex projects

Recent duplex work.

Street view render of a torrens title duplex in Mollymook
01

Mollymook duplex

Mollymook, NSW / 784m² lot / Torrens title duplex / CDC

A Torrens title duplex development delivered through the complying development (CDC) pathway.

Render of an attached dual occupancy in Sydney
02

Sydney dual occupancy

Sydney, NSW / 570m² lot / Attached Torrens title dual occupancy / DA

An attached Torrens title dual occupancy, delivered through a development application (DA).

Common questions

Duplex questions, answered.

Can I build a duplex on my block?

It depends on the zoning, the lot size and width, and the controls of your council or the state codes. The feasibility report answers this for your site specifically.

How much land do I need?

Minimum lot sizes for a duplex generally start from around 400m², but the requirement is site specific and varies from council to council, as well as between approval pathways. We check the rules that apply to your site before any design starts.

Complying development or a development application?

Complying Development is generally the faster approval pathway where a site and design can satisfy the relevant State planning standards. Where greater flexibility is required, a Development Application (DA) to Council may provide additional design and planning opportunities. As part of our feasibility assessment, we evaluate both pathways and recommend the approval strategy best suited to your site and project objectives.

What does it cost to design a duplex?

We start with a fixed-price feasibility at $4,750 + GST for a duplex outcome. It includes a fixed fee proposal for the full design, and the feasibility fee is credited against that fee if you proceed.

Do you work outside Sydney?

Yes. We regularly visit sites across Sydney, the Central Coast and the South Coast, and also work remotely on projects throughout regional and metropolitan NSW. Remote site assessments are a common part of the development process and can be undertaken with a high degree of accuracy using contour surveys, aerial imagery, planning data and site photographs. This allows us to assess development potential, prepare feasibility studies and design projects effectively, regardless of their location within NSW.

What clients say

In their words.

Richard has been instrumental in helping us navigate our duplex project from the beginning. His communication has been outstanding, and his advice and guidance have made the entire process straightforward and stress-free. We would not hesitate to recommend him to anyone undertaking a similar project.
Matthew, South Wentworthville2 × detached single storey duplexes
Richard from Keep Building Design was highly professional and very helpful when I had questions about areas of the development I wasn't sure about.

Would highly recommend his service!
Keenan, Mollymook BeachDouble storey attached duplex
Start here

Find out what your block can do.

A fixed-price feasibility report covering the planning controls, site constraints and services and their cost implications, the likely approval pathway, a concept yield sketch and a fee proposal for the full design.

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Let's make
something matter.

Call us

Sydney, the Central Coast and the South Coast, with remote design throughout NSW.