Ask The Expert
20/04/2010
How do drainage issues for green roofs compare with those for typical flat roofs?
Just as with typical flat roofs, green roofs should comply with the requirements identified within BS 6229:2003, Table 6 with regards to achieved finished falls. The primary function of a roof is to provide a watertight covering and to ensure free flowing drainage to either outlet or gutter locations.
Today, there is a growing appreciation of the benefits that green roofs can bring in reducing rainwater run-off by playing a key role in SUDS (sustainable urban drainage systems) as typically a green roof will intercept at least the first 5mm of rain in any shower, reducing run off to sewers.
They also help to reduce the urban heat island – the effect that makes cities hotter than the surrounding countryside. The greatest benefits of all come when a building is entirely enveloped in vegetation, i.e. with both a green roof and green walls, helping to keep the building cool in summer, and offer protection that makes the roof membrane last longer.
Today, there is a growing appreciation of the benefits that green roofs can bring in reducing rainwater run-off by playing a key role in SUDS (sustainable urban drainage systems) as typically a green roof will intercept at least the first 5mm of rain in any shower, reducing run off to sewers.
They also help to reduce the urban heat island – the effect that makes cities hotter than the surrounding countryside. The greatest benefits of all come when a building is entirely enveloped in vegetation, i.e. with both a green roof and green walls, helping to keep the building cool in summer, and offer protection that makes the roof membrane last longer.
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