by Brianna Crandall — August 7, 2015—With the summer months comes the mission of maintaining a facility or campus’s landscapes, including green roofs. Sasha Aguilera, a design consultant for Xeroflor Canada and an experienced green roof professional, offers tips for designing green roofs so they will require less maintenance year-round.
Some municipalities require rooftop maintenance, points out Aguilera. Toronto requires a maintenance plan in order to obtain a green roof permit. Washington, DC, requires rooftop inspections twice a year. Many green roof system warranties are tied to performing maintenance and filing reports. Ultimately, maintenance keeps a green roof alive and well, looking good and performing as it should, notes Aguilera.
The extent of maintenance depends on the design, the plant selection, the depth of growing medium, the roof’s exposure, and the weather. While it is hard to predict the weather, a designer or specifier can opt for a system with low-maintenance features to reduce overall labor and cost.
Technological advances offer low-maintenance options that do not require loose-growing medium, says Aguilera. These lightweight systems can achieve desired stormwater management goals and are easy to install and retract (if necessary). Without additional growing medium, they are said to invite fewer roof-damaging weeds and therefore require less manual labor.
Plant selection
Locally grown hardy and drought-tolerant plants such as sedum and mosses are ideal. Maintenance personnel should be familiar with green roof plants and the owner’s green roof aesthetic preference, as some “weeds” might be tolerated.
Irrigation plan
Access to water, with adequate pressure, close by the rooftop is critical for supplemental irrigation in the establishment phase and during periods of drought.
Fertilizing plan
An annual application of slow-release fertilizer, usually in the spring, helps feed plants nutrients over a three-to-nine-month period. Care must be taken to avoid a nutrient supply on plants preparing to go into dormancy in the fall season.
Weed control
Weeding is necessary on all green roofs. Without proper maintenance, invasive weeds can overtake a green roof and pose a threat to the original green roof design. Woody plants can potentially harm the waterproofing membrane. A thin-layered system with synthetic water retention layers tends to be less inviting for harmful weeds than systems with thick-growing medium and therefore require less routine, manual weeding.
Debris removal and drain inspection
Inspection of the drainage paths is very important. Blocked drains and pooling water can cause root rot, and green roof plants may drown.
Document visits
Once a properly installed extensive green roof is well established, its maintenance requirements are usually minimal. However, there should still be a person or team responsible for maintaining the system, performing visits three or four times a year. If the property does not have the personnel to do the above, it is recommended to hire a professional green roof maintenance contractor with horticultural knowledge and “working at heights” training. Each visit and recent weather conditions should be recorded. Photos are needed for future reference and any potential warranty claims.
