Green roofs

This amazing article outlines how to create a green roof on your shed. Quite amazing!
Its part of a wild London initiative, aiming to create nature reserves everywhere. Its obvious that gardens are becoming more and more vital to wildlife and people. They cool buildings, soak up water, and importantly absorb carbon. Its about time all this fuss happened.

TIME OF YEAR: MARCH-SEPTEMBER
WILDLIFE-FRIENDLY: Living roofs increase the planting area
in your garden and provide extra wildlife habitat.
CLIMATE-FRIENDLY: Living roofs absorb rainwater and can
help to stabilise the temperature of a building.
WHERE TO BUY MATERIALS: A good independent garden
centre (try to shop locally where possible).
Before you start
Is your roof strong enough? You may need to strengthen it
with timber braces. If in doubt, get professional advice. Also check
that your roof is waterproof.
Preparing your living roof
1. Make a wooden frame to fit over your shed roof. It needs to be
20-30cm deep to take liners, soil and plants. Ensure there is a
gap between the edge of the frame and the shed roof to allow
free drainage of water.
2. Line the frame with a water-proof sheet, such as a butyl pond liner.
3. On top of the sheet, add a moisture-blanket made from woolly
fleece, old towels or blankets.
4. Finish with a filter sheet (like sheets used under patios to keep
weeds out). This holds fine soils but allows water to pass
through.
5. For large or sloping roofs, add batons across the frame to hold
the liners in place.
6. Add a 4cm layer of expanded clay granules on top of the liners.
This is a lightweight substrate in which your plants will grow.
7. Finish with a 4cm layer of top soil (70%) and sand (30%).
Planting your living roof
Leave it to nature You can let plants colonise your roof from
seeds blown by wind or dropped by wildlife.
Sedums and stonecrops These plants are very drought resistant
and their flowers often attract bees, butterflies and other insects.
Grasses and wildflowers Plants of a species-rich grassland
provide nectar for insects, seeds for birds and stalks for insects to
shelter in winter. You’ll need a well-draining low-fertility soil. Sow
seeds or plant small plugs and water until established.
Extra features Consider adding shingle, crushed shell, sand and
/ or gravel areas to benefit insects, such as solitary bees and wasps.

Here's the link http://www.wildlondon.org.uk/Addagreenrooftoyourshed/tabid/419/language/en-US/Default.aspx