Nordic Copper for today’s housing

For each print edition of Building Products we will be reviewing a stand-out residential development. For the latest edition we looked at Nordic Copper’s recent project in Bristol.

A major new residential building in Bristol exemplifies the role of copper cladding to define high-quality housing developments – irrespective of tenure – with its 170m long façade clad in Nordic Brown Light pre-oxidised copper. But copper also satisfies essential performance, sustainability and safety requirements for modern housing, as architectural copper producer Aurubis explains.

Designed by Ferguson Mann Architects (FMA), the Copper Building is the second phase of Bristol’s Lakeshore residential development for Urban Splash, set in 10 acres of established landscape surrounding a lake. It follows FMA’s redevelopment of the iconic Grade II listed former headquarters of Imperial Tobacco, designed during the 1970s in the International Style by Skidmore, Owings and Merrill (SOM).

The new Copper Building replaces the SOM-designed factory, demolished in the 1990s, and provides 136 apartments for rent or for sale, including purchase through Shared Ownership. Project architect Nick Brown explained FMA’s design strategy: “The factory building that occupied the northern edge of the site was particularly significant, not just for the local area, but Bristol as a whole. Without it, the northern edge of the site felt incomplete and it was an obvious decision to create a new building, enclosing the parkland and addressing the street and retail park to the north.”

Material Context

Nick explains: “The form and language of the Copper Building were always intended as a reference to its Cor-ten steel clad predecessor. Although our initial design included Cor-ten steel cladding, as it developed, we sought a more friendly and economic material to speak of the industrial heritage of the site, yet in a warmer and more refined way – a material with some life, that would patinate subtly over time.

“The warm colour of the Nordic Brown Light pre-oxidised copper, along with the longevity, sustainability and natural credentials of copper made it the perfect choice.

“The rigorous 3.6m wide structural grid that defined all elements of the SOM-designed, Mies-inspired Phase 1 building was a key driver in the design of the Copper Building. The lake frontage is an open grid of timber-clad balconies with generous glazing.

“However, the street and end facades are more varied with a mix of 3.6m, 7.2m and 10.8m ‘design bays’, defining a mix of 1-bed, 2-bed and duplex apartment types.

“A particular design challenge was to bring some fun and visual interest to the street façade of a building that is 170 metres long. Here, the apparently random fenestration belies an underlying structure of bays and rhythmic pattern of windows and vertical seams in the copper cladding that tie everything together. The Nordic Brown Light copper cladding also continues into the
fully-glazed central atrium.”

Attention to Detail

Nick continues:“Key to the success of the building was the precise detailing and execution of the Nordic Brown Light copper cladding. For example, we avoided a crude coping on the top and instead developed a concealed parapet cladding detail so that the vertical seams silhouette against the sky, yet still achieve a robust roof-edge detail.

“At the outset of the project, the installer set out a full-size cladding bay to identify potential issues with FMA, allowing details to be refined. The new Copper Building still maintains a dialogue with the neighbouring Cor-ten clad Lakeshore building and they both sit comfortably together, just as the original factory and office did. Importantly, local feedback about the building has been really positive.”

Copper’s unique architectural qualities are defined by its naturally developing patina – which cannot be replicated successfully using other materials with surface coatings. The patina film provides impressive protection against corrosion and can repair itself if damaged, giving exceptional longevity. A complex combination of factors determines the nature and speed of development of patina over the years. So, it is not surprising that factory-applied surface treatments are popular to provide straight-away oxidisation and patination of copper surfaces to a selected level, particularly for vertical facades.

Natural Processes

With Nordic Copper from Aurubis, the processes involved are very similar to those taking place in the environment and utilise copper mineral compounds, not alien chemical actions. As used on the Bristol project, Nordic Brown products are pre-oxidised at the Aurubis factory to give straightaway the same oxidised brown surface that otherwise develops over time in the environment. The thickness of the oxide layer determines the colour – either Nordic Brown Light or the darker Nordic Brown – and the darkening oxidisation process continues in the natural environment.

Other Nordic Copper surfaces include Nordic Standard ‘mill finish’, while Nordic Green and Nordic Blue are factory-applied patinas developed with properties and colours based on the same brochantite mineralogy found in natural patinas all over the world. Essentially, they enable designers to determine both the colour and intensity of patina for each project with ‘living’ surfaces: as well as a solid patina colour, other intensities can be created revealing some of the dark oxidised background material.

Nordic Copper alloys include Nordic Bronze, an alloy of copper and tin, initially with a similar colour to Nordic Standard, gradually changing to a stable, dark chocolate brown. Nordic Brass – which can also be supplied pre-weathered – is an alloy of copper and zinc with a distinctive golden yellow colour. Nordic Royal is a golden alloy of copper with aluminium and zinc, giving a rich golden through-colour that is very stable. It retains its golden colour and gradually loses some of its sheen as the oxide layer thickens with exposure to the atmosphere, resulting in a protective matt finish.

Sustainable and Safe

Copper is a natural element within the earth’s crust with an unrivalled lifespan, no maintenance and full recyclability. It requires no decoration or cleaning, saving resources, cleaning chemicals and cost. With an ‘A1 (non-combustible material)’ fire classification to EN 13501-1, copper is also suitable for cladding tall buildings, using appropriate constructions. It is also non-toxic and safe to handle, as well as non-brittle and predictable to work. Copper’s inherent antimicrobial qualities make it ideal for touch surfaces internally as well.