Waihi Beach Green Roof
The owner of a residential property in Waihi and the architect who designed the renovation of that property, wanted to do something different rather than just a pitch roof over the garage/boatshed. After reading that living/green roofs retain up to 80% of the water on the roof and then slowly discharge it, plus consent requirements from the council for any stormwater to be managed (previously it just discharged to the street), the decision was made to install a living/green roof.
The roof was planted with a mixture of natives and exotic plants including grasses, tussocks, ground-cover and specimen plants. Irrigation was installed and maintenance visits were initially carried out every 3 months for the first 12 months following installation.
The roof was tested on 29th May 2023 (7 months after installation) when a weather ‘bomb’ hit Waihi Beach and 60mm of rain fell within an hour and over 100mm fell in a 5 hour period causing significant flash flooding. The clients and the architect were impressed by the green roof’s performance, as they watched the water from the excessive rainfall gently run off the roof and through the down-pipes for the next 5 days.
Location:
Waihi Beach
Client:
Adrian Whistler – Outerspaces Landscaping
Living Roof Designer:
Greenroofs Ltd and Outerspaces
Architect:
John Monroe – DRS Architecture
Project Manager/Contractor:
Adrian Whistler – Outerspaces Landscaping
Living Roof Type:
Semi-Extensive
Development Type:
Private/residential
Build:
Retrofit
Building Type:
Residential garage/boat shed
Living Roof Brief:
Condition for Resource Consent for stormwater management as rain draining off the roof runs straight out on to the road.
Project Drivers:
A semi-extensive living roof is located on the new boat shed building and the planting of this green roof has taken inspiration from its coastal location and from known successful NZ natives that have been used as living roof plants to create a totally native green roof which has botanical and visual links with the adjacent coastal garden design.
Living Roof Design:
300mm wide riverstone pebble margin round all 4 sides
Vegetation
Mix Native and Exotic
Cordyline Stricta Glauca
Liriope Muscari
Sophora Molloyii
Anigozanthus Amber Velvet
Lysimachia Nummularia
Zephranthes Candida
Substrate depth
150mm
Substrate composition
10 % Organic matter, 80% Pumice, 5% Zeolite, 5% Coco fibre
Drainage system
Nuralite Nuramat
Waterproof membrane
Nuralite
Irrigation
Approx 150 linear metres of 30cm spaced pressure compensating dripline operated by a Galcon blue tooth battery timer connected to tap provided.
Living Roof Construction:
Modular tray living roof system/Built-in-place living roof system
Roof structure:
Unknown
Slope of roof
<5°
Describe roof access:
Easy access from rear during construction.
Now safety glass in place so access for maintenance is by small ladder.
Climate evaluation:
Coastal and full exposure to sun and enhanced by surrounding glass and reflective white tiles.
Exposed to on-shore (northerly) winds. Sheltered from other directions
Site considerations:
Coastal site so salt tolerance important
Size:
80m²
Completion:
October 2022
