Black Mountain House


Location | O'Connor, ACT

Date completed | Jan 2016

EER | 7.1 star (started at 2.3)

Area | From 115m² to 192m²

Builder | 35 Degrees 

Images | Rod Vargas

Awards | 2017 Sustainability Awards, Single Dwelling Alteration or Addition - Finalist


A tricky brief lead to a cleverly- crafted solution

Our O’Connor clients had a keen eye for the opportunities this home had to offer; the existing home was on a large block, with a beautiful outlook on to the twisting branches of mature silver-leaf stringybarks that line the street. They wanted to retain the existing home for its character, but create a dynamic complimentary extension in to the back yard.

Unfortunately, the very characteristics that had attracted them to the area, quickly became a difficult hurdle to overcome. A large mature gum tree existed right in the middle of the backyard, and was deemed to be a valuable healthy tree by Urban Treescapes. A complex design process ensued, exploring near-impossible opportunities for extensions around the tree, and resulting in an extensive development application process to negotiate an extension that would see the large gum removed, but other trees on the site retained.

On top of this, the clients were currently located overseas, with very poor internet and an often heavily delayed phone-line. While we are now well practiced at working with overseas clients, this project was our first, and considerable effort on both the client and architect’s behalf was required to reach a high level of design resolution and satisfaction.

As we often say, the more constraints there are on a project, the more interesting and dynamic the design result will be. This house is a great example of that. The existing home was largely reconfigured internally, with a few ‘pop-outs’ borrowing a little more space under the existing roof line. The main extension in to the backyard is designed to capture the northern sun, and provide excellent connection to the outdoors and various framed views to the garden and trees. The materials and colours are bold and modern to provide an exciting and energetic new space – but they are also textured and rich to connect back to the tangible native landscape and original house.

By retrofitting the existing home, and paying close attention to the design and construction of the new wing, the home now achieves an excellent energy efficiency rating of 7.1 stars.

Through a challenging design process, this renovation and extension achieves a dramatically improved quality of life for a young energetic family; bringing them light, comfort, connection to the landscape, and creative communal spaces.


Key features

Extension: master bedroom, family room, dining, kitchen and bath

836m² sloped site with orientation of north to the side

Floor finishes include; carpet, concrete & tiles


High performance PVC double glazing

Ceiling fans and cross ventilation  are the only forms of cooling needed

R1 insulated slab

R2.5 insulation to exterior walls

R1.5 insulation to interior walls

R5 insulation to the roof space

Vapour permeable building wrap to extension walls and roof

Minimal air leakage, well sealed building envelope (9.5 air changes per hour at 50 Pascals)