Any British architect with an ounce of street cred wouldn't dream of cladding their building in anything else – not without getting their collar felt by the style police …
Until recently, it seemed that no new building could be considered à la mode if it didn't sport a few square metres of terracotta rainscreen cladding. The iron rule of fashion, however, is that things change. The opinion formers have decided that terracotta is "very clichéd and predictable", as Craig Casci, a director of architect Hamilton Associates, puts it. The really hip thing to be seen in is, or is about to be, copper.

Hamilton Associates is fairly confident about this, as it's latest project is a recently finished housing block called The Edge for Berkeley Homes, which has a block clad entirely in pre-patinated green copper. What's more, it is in Clerkenwell, north London, an area infested with happening architects, fashionistas and young British artists.

Casci chose copper because he wanted to keep the hard industrial feel of Clerkenwell. "We didn't even look at brick and stone. We went straight for metal, although brick is used at ground-floor level," he says. Three of the four blocks of the 204 unit development are clad in zinc, the fourth is copper. "Zinc is very grey and sucks up the light. We wanted something brighter and more colourful, and a material that would play off against the zinc," he says. "We chose copper as it's a good contrast to the zinc-clad blocks. It really highlights the development in the street from a distance."

The trend is also in evidence in Scotland, for similar reasons. "It's definitely a material more architects are using, particularly the pre-patinated green," says Alan Dunlop, partner in Gordon Murray + Alan Dunlop Architects. "Perhaps Alsop's Stirling Prize-winning Peckham Library is the catalyst for this." His practice designed the Radisson SAS hotel in Glasgow, which has a dramatic, curving copper-clad screen 20 m high running the length of the building. Dunlop says he used the striking green of pre-patinated copper to make the building stand out.

"Everybody builds in sandstone in the city centre," he says. "We wanted an individualistic type of building that was instantly recognisable because of all the other hotels in the area. It needed iconic status because the Hilton is 15 storeys high; the Radisson couldn't be that high because it's in a conservation area and it had to compete with that." Dunlop also liked the fact that copper is a material traditionally used in Glasgow. "We wanted a highly contemporary building with historical references; copper seemed the ideal choice."

Other architects have used copper for entirely different reasons, such is the availability of a wide choice of finishes. Chancellor's Court, a hall of residence at the University of Edinburgh designed by Oberlanders Architects has just been completed and has naturally coloured mill-finish copper. The scheme sits under a large crag called Arthurs Seat, and the natural brown of copper helps the building blend in with the exposed rock. Because the project can be viewed from above as well as at ground level, Oberlanders wanted a material that would unify horizontal and vertical elements – specifically the towers housing the students' social and catering areas. "We explored materials for these elements, seeking ideally a unified aesthetic for both roofing and cladding," says Andrew Wilmot, the project architect. "Copper was specified as the most appropriate material for this particular context."

Wilmot is delighted with the result. "Aesthetically, classic copper has been wonderful; the material is very live, responding to weather conditions with an infinite variety of colour, hue and reflectance," he says. And he likes the way the material changes over time. "We look forward to a constantly evolving building as the weathering gradually transforms its appearance." Other reasons for copper's increasing popularity is its technical versatility: it can be curved, laid as tiles, seamed either horizontally or vertically depending on how an architect wants to express a building's form and is lightweight and durable. Add to this the fact that copper is surprisingly inexpensive – at The Edge it came in at the same price as standard cavity wall construction – and it looks as if copper is going to stay in the haute couture category for a while. Casci says Hamilton Associates is working on a 300-unit housing development in Wandsworth, south London, that will have modular cladding panels in a range of copper finishes from polished through to green, "like bricks mixed up".

The laws of copper

Copper is bright and shiny when milled but changes colour as it oxidises. In two months it will dull down to brown and eventually go a vivid green.

This oxidisation process depends on local conditions: high levels of oxygen, pollution or water will speed up the process. For example, copper goes green much faster by the sea because of the salt in the air. In some places it may never go green.

Cladding naturally patinates and changes colour more slowly than roofs because water does not dwell on it for any length of time. Because of this, pre-patinated versions of copper are available for an instant aged effect. Some planners like this because they know what they are getting in the long term.

Care needs to be taken when using copper with other materials as bi-metallic reactions can corrode some metals. Copper can be used with aluminium only if the aluminium is given a non-conductive coating. If there is direct contact between the two materials a separate layer of non-conductive material should be used to isolate the two.

Water runoff should also be carefully detailed. If water runs off copper onto zinc or galvanized steel, dissolved copper ions in the water will lead to rapid corrosion. Also, water runoff from copper can contain metal dust and oxides that will stain porous materials. To minimise this, drip edges must project 40-60 mm over porous materials below.

Top copper contenders

The shortlist for the 2003 Copper in Architecture Awards has just been announced. The contenders for the Architectural Design Award are:

1 Embankment, Putney, west London, designed by Curtis Wood Architects

Brewery Square, Clerkenwell, designed by Hamilton Associates

Langdon Close Student Housing, London, designed by Feilden Clegg Bradley

Plymouth Theatre Royal Production Centre TR2, designed by Ian Ritchie Architects

Peace Memorial Park Pavilion, Leicester, designed by Patel Taylor Architects

Leaden Hall School, Salisbury, designed by Keith Harnden

Fitness Training Room, St John’s College, Oxford, designed by Gray Baynes & Shew Architects