Green Roof

The Silver Spray plan includes some flat roof areas that will have a “green roof”.

There were a wide variety of these at the  Ecobuild show. It seems there are lot of options in terms of:

  • What plants are in the green roof. All the way from tall grasses, shrubs to lower and thinner sedum matting.
  • The base system that the green roof sits on and in. These range from egg cup looking sheets to matting that the plants grow into.
The main reasons, beyond aesthetics seem to be the  biodiversity increase, sound and thermal insulation and rainwater absorption (with slow release).

I asked Robert from ra-studio about his experience with green roofs:

I have done a couple, one in Cornwall (Sea house) and one on the Lancashire moors!

Green roofs are often used to combat heavy rainfall, and stop massive water run-off into the surface water sewers.  With more and more people removing garden spaces (lawns etc) and replacing with hard paved terraces, the green roof system acts as a way holding the water back and allowing it to drain into the RW sewers far more slowly.

We used a Bauder roof at Sea House.  Bauder do basically 2 types of green roof system – an intensive and extensive system.
The intensive system is a fully blown grass roof system that allows you plant lawn, shrubs, trees etc up there, and due to the thickness of the soil (normally a min of 250mm thick), it is quite a heavy build-up.
The extensive system is basically a sedum mat that is the thin / lightweight solution.  It uses sedum / succulents in the form of a sedum mat (approx 25 – 30mm thick), and although the plants on the roof will take up some water it is far less that the full grass roof.
There is a drainage layer under the sedum mat, and any excess water that the plants don’t take up, is released into the drainage system.  See Bauder’s website

Roof Insulation

Under the green roof, there will still be thermal and water insulation. This a lot of other products were at the Ecobuild expo, “Stone Wood Slabs for a flat roof”.