This green roof was built on the old outside toilet at the New Roots shop on Glossop Road, Sheffield. The waterproof layer was laid on the roof so that it hung over all the edges. The pond liner also acts as a root barrier. Carpet was used as a moisture mat as it insulates and retains moisture during wet periods, and releases water during dry spells.
We used Floradrain, an egg box style plastic sheeting as our drainage layer. It came in strips which were cut to length and overlapped by about 5cm. This was then filled with 10mm gravel. The filter membrane came with the Floradrain – it is used to stop any debris blocking up the drainage, and to protect the pond liner from any mechanical damage. It came in strips so was cut to length and overlapped by about 10cm. It was laid up and over the frame.
Once all of the layers were put on (except the soil) the frame edges were capped with strips of tanilised timber (1"wide, ½" thick). Excess pond liner and filter membrane were trimmed off with scissors and neatened with a stanley knife.
Frame made of tanilised timber -£18
Waterproof layer - Pond liner 3mm from B&Q £21
Moisture mat - Carpet 10mm (found in a skip)
Drainage layer- Floradrain & gravel 50mm (Gravel £4)
Filter membrane 2mm
Glossop Road, Sheffield, UK
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