Designing and insuring a green roof

Compared with the barrenness of traditional roofing, green roofs are very appealing. Not only are they beautiful and bucolic, but they have also been shown to lower the temperature indoors in the summer, as well as increase the longevity and even the value of buildings. They are aesthetically pleasing, energy-efficient, and they add value – all that in addition to yielding a regular crop of vegetables and flowers. What could be better?

Unfortunately, the reality doesn’t always live up to the idyllic image. A green roof entails the artificial creation of a growing medium, which requires a hefty investment of time and money.


Lots of work ahead
First of all, the entire surface of the roof must be made completely watertight with a synthetic waterproof membrane. Water is directed toward the drain or the gutters using a second waffle-pattern drainage membrane to create a reservoir that is essential during dry spells.

A layer of geotextile fabric must be added to hold the earth, prevent water dripping, and provide a moist environment for roots, which are anchored by a second geotextile fabric that is strong enough to resist perforation.

And then there’s the final layer, the growing medium. This can become very heavy, especially when it rains which is why the experts recommend mixing composted leaves and bark with small stones, such as crushed lava or brick. The depth of the growing medium can vary from 10 to 15 cm depending on the type of plants you intend to grow.

montage-toit-vert-ENChoosing your plants carefully
Once all these steps are completed, you can choose your plants. But not all plants are well-suited to a roof. Native perennial species that can withstand extreme temperatures require the least maintenance.

To ensure their survival, the plants must be watered very frequently, especially in the first few years. If they dry out too much, not only are they liable to die, but they can also contribute to spreading fire from one building to another! Consequently it is essential to install an automatic irrigation system.


Unique risks
For the brave souls who complete all these stages, there’s one more key step to take. You must place a call to your insurer, and that could involve an extended conversation.

The insurer will raise the issue of the risk of water infiltration via the roof. The risks are still difficult to assess because there are few precedents to work from.

Anyone who is considering creating a green roof should arm themselves with as much information as possible, including reports from specialists, contractors and engineers, to give their insurer a solid overview of the plans.

Many insurers will decline to expose themselves to the risks associated with green roofs. But in some cases, they may request a building inspection report in order to assess the risks involved. It’s up to policyholders to start the discussion and provide complete information to allow the insurer to properly evaluate the risk.

Of course, all modifications to the property must be made by professionals in conformity with the applicable laws and regulations.

Contact belairdirect for a home insurance quote, or to get more information on the subject.


For help with the installation of a green roof:
In Toronto: Toronto city site
In Ottawa: Ottawa city site