Cosgrove House Woollahra, New South Wales building extension, Australian real estate architecture photos

Cosgrove House, Woollahra, New South Wales

26 September 2025

Architects: Tzannes

Location: Woollahra, NSW, Australia

Photos: The Guthrie Project, Murray Fredericks, Tzannes

Cosgrove House, Woollahra, New South Wales Home Extension

The Cosgrove House is a contemporary addition integrated with a significant building in a heritage conservation area. A high level of residential amenity is achieved on a small property located at a busy intersection.

The original two-storey 1920s residential building on the site, identified as a contributory item in the Woollahra Heritage Conservation Area DCP 2003, was converted in part to a doctor’s surgery in 1973 and then conserved and adapted to a rug showroom in 2003. The new three-storey addition comprises a two-bedroom home with large living, dining, kitchen and terrace spaces above a garage and entry.

The design aspiration was to achieve a high standard of architecture appropriate to the Woollahra context, to minimise the noise from Ocean Street and to optimise the home’s privacy.

The architecture partly inserts the new residence behind the existing building. This maintains the predominant existing elevation fronting Queen Street and addresses the scale and subdivision patterns of the terraces to the north and east of the property. The resulting form fits within the volume, scale and subdivision patterns of Woollahra.

To address street noise, an internal stair is located along the eastern boundary and together with the shopfront to the north, these elements act as sound barriers. Internal spaces are oriented to the west to optimise outlook and solar access. Appropriately designed screens and landscaping on the western boundary maintain the privacy and amenity of the adjacent residential properties.

The existing building is distinguished from the new addition through the use of concrete on the lower two floors. The third floor is contained within a lightweight copper-clad mansard roof. Long life, low maintenance and environmentally appropriate design are achieved through a combination of thermal mass, high-specification roof and wall insulation, solar screening and cross ventilation.

Cosgrove House, Woollahra, New South Wales – Property Information

Architects: Tzannes – https://tzannes.com.au/

Acoustic: Wilkinson Murray
Builder: ANT Building
Building surveyor: Denny Linker & Co
Cost consultant: Donald Bayley & Associates
Construction Manager: Anthony Gleeson
Heritage Consultant: Goddan Mackay Logan
Hydraulic consultant: Whipps Wood Consulting Pty Ltd
Interior designer: Robyn Cosgrove
Original architect: Bruce Willoughby
Structural Consultant: Benvenuti Engineers