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The invention of a 鈥渂uilding in a bag鈥� promises to revolutionise the provision of emergency shelters in disaster areas. Construction could hardly be easier: all you have to do is add water to cement-impregnated fabric and inflate it. Twelve hours later, it forms itself into a hardened hemisphere or nissen-hut-shaped structure that can serve as a shelter or a field hospital.

The idea of 鈥淐oncrete Canvas鈥� was conceived by William Crawford and Peter Brewin, two industrial design engineering students at the Royal College of Art in London. Their aim was to combine and improve on the two current methods of providing emergency shelters. These are tents, which are easily portable, but provide poor protection against the elements, and prefabricated buildings, which offer good protection but are expensive and difficult to transport. Concrete Canvas combines the best of both 鈥� it is lightweight, and so readily transportable, yet it has the robustness and security of a prefabricated building.

The Concrete Canvas is delivered to a disaster area in a plastic sack. Once it is in position, the fabric is unpacked, wetted and inflated. It remains inflated until the cement has set, and during that time the skin of the shelter is automatically optimised for tension and compression. Door and windows are provided by cutting openings in areas of the fabric not treated with the cement.

Crawford and Brewin came up with the idea as their entry for the British Cement Association/Concrete Centre annual award for innovative uses of concrete. To begin with, they were interested by the idea of using inflatable structures to halt leaks from broken gas pipes; it was only later that they examined the possibility of using the same principle to make giant concrete egg-shell shelters using inflation to optimise the structure鈥檚 compressive strength. Their idea won second prize in that competition, and went on to be awarded another from the British Standards Institution鈥檚 Sustainable Design Award, and this funded a field trip to Uganda.

There, Crawford and Brewin spent a month meeting United Nation agencies and organisations such as M茅decins Sans Fronti猫res, visiting refugee camps, and demonstrating a prototype building in a bag. Their idea was met with a warm reception. The opinion at MSF was: 鈥淚f this were available now, we鈥檇 buy 10 today.鈥�

The aid agencies were impressed by the simplicity and economy of the idea. The bag weighs 230 kg and inflates into a shelter with a floor space of 16 m^2. Cost is estimated at 拢1100 a unit, compared with 拢600 for a tent and 拢4000 for an equivalent-sized steel cabin. The shelter can also be delivered in a sterile state, which makes it ideal for emergency hospitals and operating theatres.

A patent has been applied for 鈥�