Replacing shingles and black asphalt, vegetative rooftop gardens are sprouting up across North America.

“Green roofs” reduce air-conditioning use in buildings by as much as 75%, catch stormwater run-off and provide noise reduction in urban centers. In the summer, they insulate buildings from the heat, in the winter from the cold and are desirable to occupants. And, buildings can earn a significant credit toward sustainability certifications like the U.S. Green Building Council’s LEED rating system with a green roof.

There are two types of vegetative roofing. Extensive roofs are shallow and built with low-growing grass, requiring minimal maintenance and little structural change for vegetation. Intensive roofs are built with anywhere from 4-in. to 2-ft. or more of soil and may host parks with trees and common spaces and require an even more robust structure below.

Regardless of the type, both roofs carry a number of risks for building owners and operators. The first is structural in nature. The roof must be capable of supporting the additional load of plants, soil and water, and in the case of an intensive roof, occupants, furniture and more. Designing a building capable of supporting an intensive roof may require significant structural upgrades versus a standard building. In addition, a special roof assembly with multiple layers of membranes and protective barriers are necessary to ensure the building doesn’t incur leaks.

When not properly designed, green roofs can become leaky and create significant water issues for a building. Insurance companies will want to know that proper steps have been taken to meet both building codes and best practices in the roofing industry.

Maintenance is another challenge. If not properly maintained, a green roof is more likely to leak or even catch fire. Grass, trees and plants will need to be trimmed and maintained. If the draining system fails, or isn’t up to code, other issues will surface.

Consider the following best practices when designing and installing a green, vegetative roof on your facility.

  1. Insist green roofs are installed according to FM Global standards. The “gold standard” when it comes to vegetative roofs, a FM Global certification, will ensure the roof is designed properly and contains fire resistant materials, is wind rated and more. Don’t cut corners on installing a green roof because it could easily become a major insurance headache should something go wrong.
  2. Hire an experienced contractor. Having a reliable, knowledgeable contractor will help you both during the design and construction phase, but also throughout the life cycle of the green roof.
  3. Maintain your roof. Vegetative roofs may need irrigation systems – some more involved than others. Get guidance on preventative maintenance practices and consider outsourcing the maintenance to roofers with this specialization.
  4. Invite the fire department for an onsite inspection. Share your floor plan and green roof information with the local fire department. Walk through the facility and up onto the vegetative roof with them. Show them how to access the roof. Let them come to know the unique characteristics of your facility. You don’t want them showing up on your property for the first time during an emergency.
  5. Conduct annual proactive inspections. With each change of season, during prolonged cold conditions, freezing/thawing, a wind or hail event, reinspect the roof to ensure it is performing as expected.

Contact your HUB Real Estate expert for more information on securing your property with a green roof.

1 https://nrc-publications.canada.ca/eng/view/accepted/?id=11095d5f-ac30-41f3-9340-2f2382ba40de