Extensive sedum green roofs utilise drought tolerant plant species which are typically sedum species. Grown in a shallow layer of lightweight, low nutrient growing media.
Applicable to both new build and retrofitting. Designed to replicate the benefits derived from open green spaces, extensive living roofs are virtually self-sustaining; requiring minimal maintenance and, in the vast majority of projects, no irrigation. These roofs are not designed to be trafficked and can be installed on adapted roofs up to 45 degrees.
Other reasons why an extensive green roof may be considered; enhanced sustainable drainage, improved bio-diversity, countering the heat island affect, enhance the visual amenity and well-being of occupants and offer indirect financial benefit i.e. extending the life of the waterproofing.
Planting and Waterproofing
Typically, the total depth of the green roof would be 85-100mm (12-20mm drainage layer & 70mm of substrate) and have a saturated weight of approx. 86-100kg per sqm.
A variety of hardy sedums, both native and non-native. These provide aesthetic interest and diversity. This planting can be offered at as NatureMat®, offering 95% coverage or Plug plants, offering 5-10% coverage upon installation.
Installation and Maintenance
Blackdown's systems can be installed either by their installation teams or by Alumasc's nationwide network of Registered Contractors.
Typical procedures carried during maintenance include:
- Removal of unwanted plant material i.e. invasive species (if required)
- Correction of any localised plant system problems that may have occurred post installation
- Replacement of any failed plants
- Application of nutrient source
- Removal of dead flower heads (if required)
- Inspection of rainwater outlet chambers and surrounding vegetation breaks
- Replenishment of any areas of settled substrate
As a general guide, it is recommended that maintenance be carried out two or three times in the first year and once or twice in each subsequent year but this depends on the type of system installed and the rate of plant cover.
Temporary irrigation is required for a period of 6-8 weeks until the plant material is established, once it has reached this point no additional irrigation should be required.