Is there anything I should avoid in building a green roof?
Charlie says: Yes! To build and maintain a successful green roof, there are several design and installation problems to avoid:
Avoid any design that is not properly drained.
Inadequate drainage can result in dead weight that the roof may not be able to sustain, plant mortality and degeneration of the planting media. All of which can be avoided through careful design and engineering.
Avoid using herbicides to prevent root penetration of the waterproofing.
Herbicides will eventually leach out of materials, escaping into- and polluting the environment while diminishing the root-inhibiting function of the root-barrier. When supplemental root-barriers are required, we recommend using thermoplastic membranes. Copper films are a recent development in the green roof industry, but until a proven track record is available, we warn against using said films as root-barriers.
Avoid using surface irrigation, if at all possible.
Surface drip and spray systems are expensive to maintain; do not deliver water efficiently to the roots (where it’s most needed), and waste enormous amounts of water through evaporation. Also, on surface-irrigated green roofs, plant roots tend to remain nearer the surface. This makes the covers increasingly dependent on irrigation and vulnerable to lapses in the watering schedule.
Avoid providers who only know one tune.
No one system is suited to all roofs – there are too many variations in pitch, drainage, climate and exposure, to name but a few engineering considerations. Remember, green roofs are not baseball caps; ‘one-size-fits-all’ serves the aims of the manufacturer, not the needs of the consumer.
Avoid un-integrated design and installation.
A trained, experienced green roof design engineer makes many educated decisions about materials and how they are to be used on your project. Many factors are held in delicate balance. An installer who has not been part of the design process – for reasons of cost, convenience or unfamiliarity with the process – may make changes that unknowingly undermine the integrity of the system. This is especially common with landscape contractors who have had no or little green roof experience. Also, there are often aspects of a project that only become apparent on-site. If your designer does not supervise the installation, issues that arise during the process may not be resolved properly. Choosing an integrated operation could be the difference between resounding success and spectacular failure.
Finally, avoid false economies.
Your green roof is a long-term investment. Skimping early can cause incredible problems later. The highest returns come from thoughtful design, careful engineering and stringent standards throughout the process – ensuring your enjoyment for years to come.
Please note: The information above is provided solely for general educational purposes. It is not intended to serve as a design guide. Roofmeadow takes responsibility only for green roofs designed, installed and maintained through the Roofmeadow network.