It was in the need to redo my flat roof (I will spare you the episode where my roof sank), that I became familiar with green roofs, commonly called “green roofs”. I took some serious steps, only to give up. Thus, I do not claim to be an expert on the subject, just a girl with an ecological mind who wants to renovate and who can share her recent knowledge. I would add that I had already touched on the subject last summer in an article on urban heat islands.
Did you say green roof or green roof?
I learned that there are two main types of green roofs:
- The roofs where the plants literally constitute one of the layers of the roof and extend uniformly over the surface (which includes the notion of extensive or intensive roofing, which I will not discuss here).
- The roofs which are composed of several “tubs” of plants (approximately 1 foot by 2 feet), which are affixed to a standard material, such as an elastomeric membrane. Several types of plants can make up a green roof: garden, meadow, taiga, boreal, etc. The main difference will be the depth of the topsoil (the thickness of the earth), a factor that influences the total cost of the project, but also the load on the roof. Because a green roof of the “Garden” type must have a thicker soil, to allow the vegetables to take root.
What is the “roof load”?
It is the weight that the roof is ready to receive, the load-bearing capacity. It is really important to bring in a structural engineer who can assess the current load of the roof and, if necessary, make recommendations on its solidification. You also have to decide if you want to make a roof accessible to residents, which represents a total weight of 100 lbs / ft2 for the structures, in addition to the snow loads. For a roof or a section of roof not accessible to residents, we are talking more about 40 lbs to 50 lbs / ft2.
Who do we call?
It should be expected that this is done in two stages. First, a roofer waterproofs the roof. Then, a landscaping contractor installs the green roof.
How much does a green roof cost?
According to your research, you will find quite divergent information on this subject. As each project is unique, my best advice would be to contact a roofer (with experience in green roofing) and request a quote. It will depend on the system you choose, the plants you use, the area to cover, etc. Still, be prepared to pay at least $ 20 to $ 35 CAD per square foot. And this does not include the normal roof covering. Neither the solidification of the structure. For my 400 square foot project, the cost was about $ 14,000.
You will have understood that the brake on such a project will have been, for me, the financial aspect. Never mind! In the end, my project will be a roof garden homemade , inspired by the philosophy of Urban farmers … Or Ricardo, the “ Urban farmer “. It depends on your references! Good summer! For more information, here is some additional reading on green roofs and the names of some Quebec businesses.
Other sources of information
- Article on ecological benefits
- Quebec: city of green roofs, roof terraces and garden roofs
- Reflection on green roofs and green walls
- Research on green roofs dedicated to municipal decision-makers
Quebec firms with experience in green roofs
Note: Do not hesitate to comment below in order to improve this list.