Sheds are taking on a bigger persona and are fast becoming a global phenomonon. Michelle Barrat finds out how steel is helping big sheds on their quest for world domination.

Be it large functional distribution warehouses or modern, attractive leisure facilities, steel is the number one material used in big shed construction. Its exponents claim steel excels in this field because of its versatility and flexibility. But with a warrantee period of 25 years, can steel claim to be a truly sustainable material? How are steel firms convincing their clients that designing in steel is the greenest option?

Steel frame has over the last 20 years, taken the lion’s share of the industrial market. John Taylor, senior engineer at Atlas Ward, explains its success.

For long-span structures steel is more suitable,” he says. “The client is looking for as much clear space as possible and as cost effective as possible. To create clear internal spaces needed on this kind of project, steel inherently has these long-span attributes. If you were doing the same thing in concrete, you would have more columns and a lot more issues regarding column sizes.”

Bob King, business development manager at Billington Structures agrees. “I really think for this particular type of structure, steel is the most effective construction material,” he says. “Concrete cannot span anywhere near as far.”

High on clients’ “must have” list is energy efficiency and sustainability, and steel is definitely ticking the boxes on both counts. This, says Paul Hanratty of roofing and cladding firm CA Building Products, can be achieved through steel cladding. “If these mega-sheds are going to get built, the manufacturers and contractors are going to have to demonstrate their eco-credentials,” he says.

With environmental concerns of utmost importance, the response from government has been to further raise minimum standards for energy efficiency for buildings and encourage renewable energy generation systems such as solar panels and wind turbines. Steel framing and cladding could provide the scope, with other materials, to design buildings with low overall environmental impacts.

Reducing heat loss is one way a building can become more energy efficient. Other ways include installing photovoltaic panels and combined heat and power plants, improving natural lighting, and introducing energy-efficient electrical appliances. Heat can escape from a building through the walls, roof, floors and windows, so the efficiency of the cladding can reduce the building’s overall energy use. Insulating the external envelope and increasing its airtightness are the two main ways to reduce heat loss.

Prologis Park in Dunstable is the site of two new distribution warehouses with a combined floor span of nearly 800,000m2. Maurice Dalton, Prologis first vice president, commercial, says improving airtightness and allowing more daylight into the buildings have improved their efficiencies. “We’ve increased roof lights and improved the airtightness to provide a relatively low energy use building,” he says. “In terms of warehouses, very rarely will they need lighting to be on and they can operate un-heated.”

He says the buildings stand out for their energy efficiency, and score very highly under the Building Research Establishment guides. “We have an excellent Breeam rating, which is quite unusual for industrial buildings,” says Dalton. “It’s obviously designed to be a very efficient building in use in terms of energy.”

King also points out how important energy efficient efficiency is when designing and constructing large industrial buildings. “We try to incorporate as many roof lights as possible,” he says. “These let as much natural light into the building so energy is not needed for lighting during the day.

“Some of the new designs for these big warehouses have got solar panels on the roof. Because it’s such a massive area it will provide enough energy to light up the building at night.”  King says heat reflected from the roof can also be recycled to heat water, which is run through energy-saving systems inside the building.  Designers are also considering installing wind turbines on top of the roofs of some buildings, King adds.

However, the steel construction sector recognises that its responsibilities do not end with a finished building. Sustainable buildings are those that are adaptable and flexible. “Steel does use quite a bit of energy to manufacture,” says King. “But once it’s been manufactured it can be recycled and reused. You can melt it down a number of times and use it again. It’s almost an infinite product and an infinite resource.”

Nearly all steel used in buildings is recovered, with 10% re-used and 84% recycled. Steel products can be re-used or recycled without the material losing any of its properties. Steel-frame buildings are adaptable, which creates much more sustainable structures, says King. They can be easily modified and adapted so that the life of the building can be extended by accommodating changes in use, layout and size.

“Lately, a lot of the big shed customers have asked for mezzanines to be put in to accommodate cafes, dining areas, shopping areas,” he says. “So although big sheds are just big envelopes, they’ve got a very effective and flexible floor space inside. You can add mezzanines, you can cordon off areas and do whatever you like if you have the ceiling height.”

At the end of the useful life for buildings, steel components can be dismantled relatively easily, Dalton says.He says Prologis buildings are specifically designed to be dismantled and re-erected. With 25-year warranties being issued on new shed constructions, contractors are putting a lot of faith in the longevity of these steel structures.

With increasing land costs, designers are building upwards as well as outwards. “We’re already talking to some of our customers about multi-storey warehousing,” says King. “So not only have you got a massive footprint, you’ve also got three or four floors inside.”

Where the UK is looking at two and three-storey sheds, seven storeys are not unusual in Japan. But with the growth of out-of-town retail, commercial and manufacturing developments in this country, it could also be a reality in the UK.

The scope for big sheds is immense and steel has a huge role to play in its development. Changing work patterns, new technologies, changing demographics and new legislation are all putting greater demands on creating sustainable buildings. To achieve this, it is important that buildings can accommodate future changes. By doing so,they will last longer and prove themselves a greener option for designers.