Step-by-step
1. Overview
Typically the studded, perforated Oldroyd Xv20 GreenXtra membrane is laid over a suitable exterior grade flat roof waterproofing membrane. This provides waterproofing and drainage for the roof. Oldroyd TP filter fleece is laid on top of the drainage membrane, followed by roof soil and plants.
2. Materials required
Good quality exterior grade flat roof waterproofing membrane, root barrier (if required), Oldroyd Xv20 GreenXtra drainage membrane, Oldroyd TP filter fleece.
3. Preparing the roof - 1
The roof would typically be constructed from a timber or concrete deck. Ensure roof and structure are strong enough to take the saturated weight of soil and plants (check with supplier). It is recommended that there is a minimum 1∞ pitch to prevent ponding on the roof.
4. Preparing the roof - 2
Perimeter upstands will be required to retain the soil and plants. Ensure the draining edge is perforated or a gap is created to allow free drainage of excess water off the roof.
5. Waterproofing
The roof should be waterproofed with a good quality exterior grade flat roof waterproofing membrane, for example FDT Rhepanol HG. Any roof penetrations should be waterproofed accordingly. It is recommended that the waterproofing is carried out by an experienced contractor. If the waterproofing layer is not a root barrier in its own right, then a physical root barrier should be installed on top of the waterproofing.
6. Guttering
Guttering should now be installed if required.
7. Oldroyd Xv20 GreenXtra - installation
The Oldroyd Xv20 GreenXtra sheets are loose laid on top of the waterproofing/root barrier. Note that the sheets will be held in place by the weight of the soil and plants.
8. Oldroyd TP filter fleece
The Oldroyd TP filter fleece is rolled out over the drainage membrane as shown, and returned up around soil or perimeter upstands to prevent any soil loss.
9. Gravel border (optional)
A 300mm gravel border is recommended around the perimeter to provide ballast, prevent soil erosion at the edge and act as a fire-break.
10. Ready for soil and growing medium
The construction, waterproofing and drainage is now complete and ready for the application of the soil and plants.
11. Soil
The roof soil or substrate is then placed on top of the filter fleece.
12. Spreading
The soil or substrate should be spread evenly to a suitable depth for the plants. This will vary according to the chosen plants (check with your supplier).
13. Plants - 1
Finally the plants are installed. In this case small shrubs have been chosen.
14. Plants - 2
In this case, a sedum blanket has been laid out.
15. Plants - 3
Here a biodiverse roof has been created. These can be designed to form habitats for specific species (consult an ecological specialist for more information).
16. A completed roof
