Whether left to form a natural patina, or powder coated with vibrant colour – metal adds modern glamour and shine
Forget corrugated iron industrial sheds or even ecclesiastical lead roofing, metal as a surface material is entering a new age. Big-name architects like Frank Gehry have shown how striking and versatile metal cladding can look – think of the shimmering titanium skin of his Guggenheim museum in Bilbao, or of the rough orange-brown curves of Thomas Heatherwick’s shell-shaped East Beach Cafe in Sussex. But metal cladding needn’t be limited to public projects. The very same materials can also be used on domestic buildings, where metal can bring a glimmer of magic to a suburban street.
Steel – A relatively cheap metal, but it needs to be treated to prevent it from rusting. Stainless steel is more expensive but creates a striking reflective effect. You can embrace rust by using corten steel, an alloy which forms a stable outer layer that is weather resistant and a beautiful browny-orange colour.
Aluminium – Popular due to its lightweight, high-strength, resistance to weathering and ease of forming. It is more expensive than steel but is seen as a higher quality material.
Titanium – Metallic shimmering white in colour, it has the highest strength to weight ratio of any metal and is corrosion resistant, even in marine environments. The downside is that it is hugely expensive.
Copper – Turns its idiosyncratic vibrant green when it oxidizes, a process usually achieved with chemicals rather than waiting around for it to react to the air. This green verdigris is highly corrosion resistant. Copper doesn’t react with water, but water running off copper can react with and stain other materials, leaving a green streak behind – a factor to bear in mind when designing your cladding.
Bronze – A copper alloy, with tin usually the other main ingredient. Untreated, the burnished tone turns to dark blue/green.
Zinc – doesn’t need treatment against corrosion. It keeps its slate grey colour through oxidisation, only dulling slightly.
Brass – An alloy of copper and zinc, brass is stiffer and cheaper than copper and the patina it forms is a subtler blue.
Metal isn’t the cheapest choice of cladding, and prices will vary depending on the amount of each type available on the international market. Titanium is bank-breaking, but copper, zinc, brass and bronze are more manageable. Using alloys rather than pure metals is one way to bring costs down. Raw steel is the cheapest option, but has the highest risk of destructive corrosion.
Metal can be used in two different ways. Stronger, less easily malleable metals like steel, aluminium and titanium can be formed into discrete cladding panels and hung from the frame independently. Softer metals like copper, zinc, brass and bronze aren’t strong enough to be used in sheet form alone, and a layer of the metal is fastened over ply boards, which are then in turn fixed to the frame.
Cladding providers sell systems with rails and fixings, and you can order bespoke sized and finished panels to suit your project. Panels can be used to create a non-sealed rainscreen, welded together, or even lapped like tiles. For an industrial or agricultural look you can even use corrugated metal. Metal shrinks with temperature change, so it’s best to put a waterproof membrane even behind a welded system.
Different finishes can be applied to metal to avoid corrosion. Steel is often galvanised, which means it is coated with a thin layer of zinc. It can also be powder coated to add colour – a much tougher alternative to paint. Aluminium can be anodised – a chemical process which bonds the protective coat to the top molecules of metal, making it very tough. However, the colour spectrum is limited to metallic shades, so powder coating is better for vibrant tones. Copper, brass, bronze and zinc are usually chosen for aesthetic reasons, so it would defeat the purpose to cover up their beautiful colour and sheen.
Words: Joanna Booth