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'Few new roofing products are introduced because people are too worried about roofs going wrong to innovate, ' a roofing expert told me recently. One company that may benefit from this reasonable conservatism is German manufacturer FDT. It has been producing its Rhepanol polyisobutylene (PIB) membranes since the 1930s. With existing roofs up to 50 years old, recent tests show that they are not only still serviceable, but new elements using today's formulation can be fixed to them easily.

This longevity means that export manager Patrick Faramia is willing to accede to the UK's ridiculously long warranties, albeit with a look of weary indulgence. 'They are normally only 10 years in Europe, ' he says, 'or five in Germany'.

FDT has recently entered a new area where warranties are seen as crucial: green roofs.

Although there is nothing inherently difficult about green-roof design, it is essential to get it right. Problems are hard to trace, and remedying them involves removing the plants and growing medium before you can get to the roofing material itself. In FDT's case, offering a greenroof solution has led to the creation of a new product that can be heat sealed, as the selfsealing provided on its standard PIB membrane does not create an adequate root barrier.

In her report on the AJ's conference on green roofs (pages 42-43), Hattie Hartman examines the barriers to their widespread adoption in this country. Although financial incentives would be nice, if unlikely, other hindrances, such as an overall lack of understanding and the fact that most guidance is available only in German, are easier to rectify. Equally important is the need for more good completed projects. There may be little chance or need for an entirely new roofing technology, but green roofing shows how, with understanding and imagination, we can develop what we have already to provide new, beneficial solutions.

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