Uprooting of trees to create space has been a standard practice in the building industry for as long as it has existed. In recent times, with growing awareness about sustainable design practices, architects and builders everywhere are trying to create structures that embrace existing treescapes, instead of replacing them. The Pepper Tree Passive House in Unanderra in Australia, by architect Alexander Symes, is one such example of this concept of sustainability put into practice.

The house is best described as an angular extension to an existing house, acting as a secondary dwelling, home office, and the occasional vacation rental. Designed in close collaboration with local builder Adam Souter, Symes' biggest challenge is building within the structural root zone of a tree. "This was our first passive house process and also our first time building within the structural root zone of a tree, so there were many new challenges and we are delighted with the collaborative process between the builder, architect, engineers and the client that has resulted in this amazing home that we are very proud of," shares Symes.

In addition to utilising the elements of sustainable architecture, there is an intentional effort in making the 60-year-old pepper tree the main design feature of the house. It stands tall through a hole in the central deck with the house existing in two parts on either side of it. The planning and interior design of the house are simple and effective. It comprises a kitchen, a living area, a bedroom, a bathroom, and a laundry. The central deck, under ample shade of the tree, provides opportunities for outdoor seating.

Since the plot is steep, the building is raised to meet the tree canopy and match the height of the existing house. Both sections of the house jut out as cantilevers and linger over the pathway leading to the entrance. The roof, where it meets the tree, becomes a roof garden with drought-tolerant native plants and is designed to collect excess rainwater that is then used in the house.

Through a thoughtful design that works toward preserving the natural biodiversity of the site, it is the material palette of the house that truly stands out. The exterior wooden cladding, chosen as a response to the pepper tree, is charred to create a waterproof outer surface. This is a Japanese technique called Shou Sugi Ban. In addition to creating a waterproof envelope, it creates a robust aesthetic. 

‘The Yakisugi cladding was selected as it is a renewable material with low embodied energy, low maintenance and termite resistance. However, it's also about how it responds and respects the pepper tree. The pepper tree’s bark is almost black and the way this cladding echoes the hero of the project (preservation and celebration of the 60-year-old tree) and the way the green leaves of the tree play with the green roof, means that you really feel emerged in a natural environment, almost akin to walking through a forest post a recent bushfire," adds the Australian architect.

The house predominantly uses salvaged and 'waste' materials, much like the recycled sandstone bricks used on the floors and walls to break the monotony of the timber clad interiors. All the materials are used to further enhance the sustainable design of the residential building.

The bedroom is compact, and the living area hides a workstation in one of the cupboards. The kitchen boasts of a breakfast nook that looks out to the nearby Mount Kembla. The house uses a variety of small and large windows to create a light and airy atmosphere in an otherwise limited space.

The Pepper Tree Passive House is the winner of the Sustainable Architecture Award 2022 from The Institute of Architects NSW. It is clear from the planning to the material selection, that it was designed to be a climate-responsive design that is considerate towards the environment and its inhabitants alike.

Project Details

Name: Pepper Tree Passive House
Location: Unanderra, Australia
Year of completion: 2022
Architect: Alexander Symes.
Builder: Souter Built
Interior Design: Paiano Design
Structural Engineer: Northrop
Landscape Architect: Grant Clement