Came across this whilst browsing its an inflatable tent, waterproof with a concrete permitted canvas outer ...inflate soak and gives you a hardened rigid building.. Make a damn good bike shed lol... Not sure about price...
http://www.welldonestuff.com/2013/03/amazing-new-concrete-tent.html
How does it deflate or is it disposable? lol
Maybe it's like the *prefabricated buildings that were erected during/after the war, built for temporary accommodation but still going strong.
* I was born in one
...inflatable tent, waterproof with a concrete permitted canvas outer
that's why I thought the outer layer was concrete, and inner layer not, hence my Q about deflation.