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Unit 1, No.103 Railway Road (North) MULGRAVE NSW 2756

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New Duplex construction in Windsor

Duplexs & Multi-Unit Developments

O'Mara has been building multi-unit developments of various types for over 55 years. We have built townhouses and duplex's of many different styles and designs. Some on sloping blocks, flood affected sites, battleaxe blocks, narrow blocks and in aircraft noise area's. 

Richmond townhouse development

Townhouses in Richmond

Duplex in Windsor

Windsor townhouse unit


These can be Strata Title, Torrens Title or Community Title, Each local council will have specific requirements (development control plan or DCP) that need to be meet. Local council also require that the construction process is completed with all landscaping, new fencing and driveways completed. These cannot be delayed until a later stage like many home owners do. We recommend that a "draft concept" plan be first prepared to evaluate the development.

Duplex's can be in the following forms;

  • Attached
  • Detached
  • Strata title
  • Torrens title

Each type of duplex will have different council requirements and design restrictions. For example in some areas 450m2 of land is required for attached dual occupancies and 600m2 of land is required for detached dual occupancies


Multi-unit development in Windsor

Duplex in Windsor

Duplex in Windsor

Single storey townhouse unit


Some building companies advertise that they have standard designs for multi-unit developments, namely duplex's but simply they will not work. There are too many external factors that need to be considered for multi-unit developments that are not required for single dwellings. Each local council has its own DCP (Development Control Plan) that is specific to its area that needs to be complied with. This is usually the size of a Sydney phone book and outlines many requirements that need to be adhered to, including items such as streetscape, north facing living areas, setbacks, car parking, building height envelopes, just to name a few. This means that each multi-unit development must be design to suit the site and local council conditions.

The best method is to first have a "concept plan" prepared by and architect or draftsman. This is a basic plan with minimal dimensions but drawn to scale. It will only consist of simple floor plans, a couple of elevations and a site plans. From this "concept plan" the builder can price the project exactly, cost alternative and obtain verbal council approval. Only then would final building plans be prepared for council development submission along with other professional designs.

Every local council has different rules when it comes to designing duplex's. Some building companies advertise that they have standard duplex designs that will suit your block of land. However in reality all duplex's will need to be designed to suit the site conditions and the local council requirements as every project differs greatly. Items that will need to be considered include;
  • North facing living areas
  • Neighbours privacy
  • Streetscape
  • Setbacks
  • Building height envelope
  • Car parking & turning circle

Our most recent duplex projects include ;

Duplex at 421 Sydney Road, Balgowlah (near Manly)

New Duplex 610 George St, South Windsor (Intersection of George & Macquarie Streets)
New Duplex 608 George St, South Windsor (Intersection of George & Macquarie Streets)
New Duplex Bradley Street, South Windsor
Duplex at 55 McGrath Road McGrath's Hill
Duplex at 11 Ilma Close, McGrath's Hill
Renovation of existing house and construction of a new dwelling to create a detached dual occupancy at 7 Maurice Street, St. Clair
Detached dual occupancy at 21 Ocean Street Budgewoi


These projects can be very complex. Each local council has a development control plan (BCP) that needs to be complied with. Issues that need to be addressed include;

  • Designated areas of multi-unit development as indicated by council
  • Streetscape
  • Neighbours privacy
  • Shadowing and North facing living areas
  • Stormwater detention
  • Site levels
  • Environmental effects
  • Car parking
  • Building height envelopes and fencing
  • Disabled access
  • Private open space
  • Sewer design
  • Heritage issues
  • Existing trees on site
  • Acoustic issues for aircraft, traffic or rail
  • Landscape design
  • Fire safety
  • BCA (Building Code of Australia)
  • Sydney Water Section 73 fee's
  • Integral Energy Compliance of Level 3 upgrade to mains power
  • AGL & Telstra compliance certificate
  • Payment of council Section 94 contributions for open space & recreation
  • Private certification fee's for issue of construction certificate, inspections during construction and issue of occupation certificate
  • Home Owners Warranty insurance policies
  • Legal fees and real estate agents commissions
  • Borrowing and finance fee¡¦s from lending authorities

With so many issues to consider it is difficult to budget for construction costs unless "Concept Plans" are first prepared. These concept plans can be viewed by council at a panel meeting to obtain verbal council approval. Only then can an accurate construction cost be estimated.

Our most recent multi-unit projects include ;

  • 8 townhouses at 182 March Street, Richmond
  • 6 townhouses at 161 Francis Street, Richmond
  • 6 townhouses at 13 Moray Street, Richmond
  • 6 detached houses at 10 Arndell Street, Windsor

New Duplex construction in Windsor

Two storey duplex in the Hawkesbury

Good economical home in Penrith

Basic construction