Green Roof Shelter Over Seating

Category: Green Roof, Brown Roof & Eco Roof

Garden Design Project: GRFGGD001

This semi intensive green roof project was created as a sun and rain shelter over a seating area with an average growing medium depth of 100mm.

In this case it was decided to use 125mm square pressure treated posts set in 60cm compacted type 1 - No concrete necessary.

The main garden structure was built and then 150mm cross members placed at right angles with a generous overhang. The pitch, allows for drainage and a greater overall visibility.

18mm ply was laid as the main substrate with screws driven in about 5mm under the surface.

Landscape fabric was then laid to ensure that screws and splinters did not puncture the liner.

An up stand was created around the perimeter using arris rail which is ideal for this purpose. A hole for drainage was drilled at the lowest point. The next step was to lay the liner.

In this case thick gage polythene was sufficient. To protect the polythene from stones or roots, a layer of pond underlay was placed on top of the liner (it is basically the reverse of installing a pond).

Next capillary matting was laid. This will retain moisture for the roots.

For other projects I have used a system of EPDM rubber pond liner with a plastic drainage matt that retains a certain amount of water.

The liner was then clamped and sealed at the drainage hole by using a bath outlet. I then attached a rain chain that guides the water into a water butt.

When using EPDM liner you can purchase internal drainage spouts that glue to the liner.

The growing medium is a mixture of expanded clay pellets and composted bark.

A drainage layer of gravel was first added to the perimeter then the growing medium was spread over the structure.

It is good to allow different depths in places. Once the entire growing medium is up on the roof and the liner is stretched to its maximum, the facia board is added; this will clamp the liner in place and give a neat finish.

It is now ready for planting. I placed an old piece of bog oak on the roof (good for insects and birds etc). Plants include herbs such as Thyme and Lavender.

For this green roof a mixture of grasses i.e. Festuca Glauca, Bulbs, Alpines and Sedums were used. It is also interesting to see what plants are establishing naturally. In this case some sedge grass and even a pyracantha! This in principle is how a brown roof is created.

Submitted By: Mark Tolfree Dip GD (Inst.GD)
Website: www.gabriola.co.uk

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