Great Notley's hall: Not a flat roof in sight

His firm has just completed a primary school for a new village in Essex whose award-winning design incorporates a German "green" roof - it has plants growing on it.

"They're sedums, which are small alpine plants. The good thing about that is you are replacing the lost ground, if you like, so there are insects in this small ecological infrastructure on the roof.

"But you also protect the roof membrane. The big damage to roof membranes is done by ultraviolet light and if you protect it with a layer - we've got a granular layer with organic material and sedums on top.

"It protects the membrane from ultraviolet light, and that's the big destroyer of flat roofs.

"It's slightly more expensive in capital cost but it does extend the life of the roof."

Cardboard classroom

If you think a "growing roof" is odd, another Essex project being backed by the Department of the Environment seems almost guaranteed to cause problems down the line - a school building made of cardboard.

Westborough Primary in Westcliff-on-Sea is to get an after-school club with changing area, kitchenette and toilet block made from 90% recycled card.

It is an experimental "sustainable construction" scheme. Consultant engineers Buro Happold think they can coat or treat the cardboard to make it waterproof and sufficiently fire-resistant.

The department hopes to have a design others can use to save time and costs by removing the need for tradespeople such as bricklayers and plasterers.

Project manager Andrew Cripps said: "Cardboard is made from waste paper, and as a construction material is therefore both cheap and very green."

The challenge was to explore the strengths and limitations of cardboard in a real, useful building.