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An internal monologue on copper COMMENT
Copper has seen a dramatic change in use from its historic place roofing prestigious buildings to being a thoroughly modern external skin for contemporary architecture. But its role as an interior surfacing material is also growing, presenting new opportunities and challenges, explains architect Chris Hodson
A
rchitectural copper is characterised by the natural development of a distinctive patina with colours changing over time, dependent upon local environmental conditions
and air quality. Within a few days of exposure to the atmosphere, the surface begins to oxidise, changing its colour from the ‘bright’ mill finish to a chestnut brown, which darkens over several years to a chocolate brown.
A complex combination of factors determines the nature and speed of development of patina externally. Continued weathering can eventually result in the distinctive green or blue patina seen on older roofs. Some rainwater is needed for the patina to form and its rate of development will depend on the water ‘dwell time’ on each surface. So, vertical cladding and sheltered surfaces will take much longer to patinate naturally than exposed roofs – while protected areas such as soffits may not patinate at all. Obviously, copper used internally and away from the outside environment will not change and develop in this way.
Modern factory-applied surface treatments can provide ‘straightaway’ oxidisation and patination of copper surfaces to a selected level. Essentially, they bring forward the environmental changes without taking away the integrity of copper as a natural, living material and are not coatings or paint. It’s important to remember that on-going changes to pre-oxidised and pre-patinated copper, as well as alloys such as brass and bronze, will continue over time depending on the local environment. Again, this does not generally apply to interior applications.
Copper and its alloys already enjoy a long heritage inside buildings, contributing a distinctive tactility to door furniture and handrails, and visual richness to lighting and other fittings. Now they are also used as high-quality coverings for walls, doors, ceilings and other interior surfaces, exploiting the materials’ inherent antimicrobial and fire-safe performance. Internally, copper can be used in a wider range of forms, enjoying freedom from the constraints of weather-proof detailing. Having said that, material continuity is a recurring architectural
theme, with external copper cladding continuing inside, simply separated by glazing. Here, it is essential for designers to understand and, indeed, celebrate the divergent developments of internal and external copper. This approach is demonstrated in a recent
INTERIORS
The redevelopment of Onslow House Guildford, designed by architects AWW, uses copper cladding to link outside and interior spaces © CGL Facades
ADF OCTOBER 2019
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