Below are example of the projects we have worked on.
Location: 6 Henderson Valley Road, Henderson
Client: Waitakere City Council
Contractor: Greenroofs Ltd
Sub-Contractor: Auckland Irrigation Ltd
Green Roof Type: Semi-intensive roof on 4 year old building
Growing medium depth: 100-150mm
Size: 350m2
Completion Date: July 2010
Development Type: Commercial office space
Irrigation Brief : Despite receiving relatively high rainfall and comprising NZ native plants the Waitakere City Council green roof had suffered from a lack of water and the Council did not have the time or resources to manually water it.
Auckland Irrigation were approached and asked to irrigate the existing green roof with an automated irrigation system so that no pipes were visible and ensuring the most efficient use of water.
In addition all work was to be undertaken without making any mess in the building interior and with minimum disruption to everyday council business.
Irrigation Design: It was decided to use “Eco-rain” irrigation blanket – supplied by Maccaferri. This comprises of two lines of conventional dripline sandwiched between two layers of geotextile ‘fleece’. To achieve optimum results the irrigation blanket should be on top of a minimum growing medium depth of 30-50mm with the remaining 100mm plus of growing medium on top of that.
Without a mains power supply it was decided that the irrigation should be split into 4 ‘zones’ and would be operated by a 4 station Hunter Smart Valve Controller (SVC) running in conjunction with a rain sensor. This is powered by a 9 volt battery which lasts at least a year. The timer allows up to 9 start times per day for each zone and for a duration of 1 minute to 4 hours.
Installation: The clay balls on the surface were raked off and bagged. All plants were carefully dug up and stored elsewhere on the roof. The growing medium was then removed to a depth of 50mm along one edge of the roof and the irrigation blanket unrolled and the growing medium placed back on top. Each end of the irrigation blanket was exposed to connect with a water supply at one end and flush and cap off at the other end.
This was repeated over the whole roof. In addition extra growing medium was added to create ‘mounds’ and additional plants were added.
Results: One month after installation there was no indication of the work or of the irrigation system. Plants have flourished and weeds have diminished. As a consequence birds and insects have been found colonising the roof. The plan is to eventually release “skinks” onto the roof in their own pest-free habitat.
