A big vision and a tight budget have resulted in a cliff top container home that breaks the mould of conventional housing design in the suburbs.

Architect Dirk Coetser from Architecture for a Change, challenged perceptions through the recent design and construction of an off-grid Northcliff hybrid home sculpted from lightweight steel and anchored by reused industrial shipping containers.

“We wanted to create something unique within the conventional suburban area. Most of the South African market is very conservative when it comes to new ideas, products and methods. We wanted to challenge the conventional notion by providing alternatives that prove to perform better and are more affordable. Many people in the housing market make their decisions based purely on aesthetics. We wanted to create an aesthetic that was driven by performance,” Coetser says.

Contained design          

The aptly named Cliff House is perched on the edge of a steeply sloping hill. Completed in early 2017, it is a response to a client brief that called for the contemporary design of a three-bedroom open-plan house, which would offer significant sustainability features, while also using an alternative and swift method of construction.

After exploring alternative construction methods that included the use of rammed earth and straw bales, client Mary Driscoll ultimately opted for light gauge steel and industrial shipping containers.

“I was looking for an alternative and fast method of construction with a big element of sustainability. A green architecture approach with a modern 21st Century spin,” Driscoll says of her initial brief to the firm.

“I stumbled on a YouTube video which showed a house being built in America using light gauge steel. I did more research on this method of construction and found that it conformed to almost everything I was looking for,” she outlines.

In his contemplation of the project, Coetser was guided by a design philosophy that relates to critical regionalism within architectural theory – a progressive approach that seeks to provide architecture rooted in the modern tradition, but tied to geographical and cultural context.

Coetser selected lightweight construction methods to reduce the impact on the site, minimise the use of concrete foundations and to accommodate the site’s extreme elevation. Architecture for a change acted as the architect, contractor and sustainability consultant on the project.

The house is raised from site using shipping containers, which cantilever over the steep slope. This allowed the house to “touch the earth lightly”, therefore minimising environmental impact. Reusing shipping containers proved to be more cost-effective compared to using a conventional cantilever beam or slab. The structure of the container itself creates a deep structural “beam”, says Coetser.

“We incorporated two used shipping containers as structural cantilever elements”, explains Coetser.

The 12m x 2.4m containers, priced at about R30 000 each, were sourced from local container reseller Absolute Containers and are dubbed “one trippers” – containers used as transcontinental packing boxes that have only made one trans-oceanic trip to South Africa and are practically brand new.

Described as a medium-cost development within the off-grid realm, Coetser says a conventional house with a similar level of finishes could easily cost between R10 000 and R15 000/m2, while the design and construction team on this project achieved a range of between R7 000 and R8 000/m2 .

Thermal insulator

To achieve good thermal performance for the house, a lightweight steel sub-frame was constructed on the interior container walls before a reflective foil insulation sheet was installed. The frame was insulated with a wool-like insulation manufactured by Isotherm from up-cycled plastic bottles.

The interior layer of the wall is comprised of a fire-resistant gypsum board, which is affixed to the inside of the steel frame, while an additional ventilated cavity keeps the house cool in the hot Highveld summer months.

The design team further challenged the idea that corrugated sheeting is an inferior product by using Safintra clip-lock steel sheeting to clad portions of the building, providing a modern aesthetic and ensuring the development was kept within its R1.4million total budget.

Internally, the floor is finished with 4mm Amorim up-cycled cork tile manufactured as a by-product of the corkscrew-making process, while Rhinowood timber decking extends from the interior living space to an external deck.      

Off the grid

Incorporating environmentally friendly features and energy-efficiency posed an intricate challenge for the design and build team, but has given rise to a completely off-grid family home.

Solar provider Eco Navitas installed a sophisticated R200 000 solar energy system, which includes a rooftop solar panel array of twelve 265-Watt Canadian solar panels with an average production potential of over 500kWhs per month ­– exceeding the expected energy needs of the house.

Additionally, an 8kWh lithium-ion phosphate battery bank charges from solar power during the day and runs the entire house at night.

The solar system includes a web-based monitoring tool for checking performance and alerting the owner to any problems on-site.

With no municipal water connection, the Cliff House’s water reticulation system draws water from an on-site borehole before being stored and purified, while water is heated in a 200-litre north-facing solar geyser.

Low-wattage LED lighting is fitted throughout the house, while the oven and stove are gas-powered.

Additional heating and cooling systems are not needed as all the windows were placed strategically to optimise natural cross-ventilation in summer and the house is fitted with double-glazed uPVC windows, heating the house in winter and cooling it in summer.

Containing the challenges

Reflecting on the project, Coetser says the relatively tight budget, along with the “big vision”, posed a specific challenge.

“The steep and rocky site was challenging, but this gave birth to an interesting design. As the process could be seen as ‘treading on new ground’ in our context there were many small challenges that had to be resolved creatively.

“The empty site was surrounded by homes with people living in them, therefore caution had to be taken not to disturb the surrounds during construction.”

While the development is currently unrated by the Green Building Council South Africa (GBCSA), Coetser has not ruled out the possibility of pursuing a rating in the future.

By Natalie Greve

See earthworks magazine issue 38 June-July 2017 for the full feature.