If you love to garden, you may like the idea of planting your very own rooftop garden. A green rooftop is simply a roof that is covered with various kinds of vegetation. They consist of a waterproofing membrane and a drainage system that helps excess water to run off the roof smoothly. Rooftop gardens are becoming more and more popular, as they benefit Mother Nature and are aesthetically pleasing.  It might sound a bit complicated, but it really isn’t if you simply learn a little bit about it.


You might wonder why people would want a rooftop garden.  There are several great reasons for planting such, as they absorb rainwater, create a wonderful habitat for wildlife, and provide insulation that will benefit the home.

You can plant an intensive roof, which are green roofs that are quite thick and will support many varieties of plants.  These types of green roofs require more work and maintenance. You can also plant an extensive roof, which is a green roof that consists of a light layer of vegetation.  These roofs are lighter than the intensive roofs and are possible on a roof that has a pitch of up to 30 degrees.  If by chance you want an intensive roof and you do not think your roof has enough support, you can potentially reinforce the roof from the attic.

Green roofs are basically comprised of five components:

  1. Weatherproof membrane.  At the base of your green roof, you will put down a weatherproof membrane to keep water from penetrating your roof. You could use asphalt roofing, a pond liner, or a fluid-applied waterproofing membrane.
  2. Root-protection barrier. If your barrier has bitumen or asphalt, you will need a root-protection barrier.  There are some recycled single-ply membranes out there, but not nearly enough just yet.  The most common root-protection barrier is PVC of 1mm thickness.
  3. Drainage layer. You want excess water to run off the roof, so adding a drainage layer is optimal. If your roof’s slope is more than 7 degrees, you may not need such a layer. In order to add a drainage layer, you can use a channeled flat plastic material or a bulky substrate. Common layers include lava stone, gravel, pumice, vermiculite, and brick rubble. Some people are now using a newer layer that is comprised of a pre-seeded extensive mat. All you do is roll this layer out on the roof.
  4. Growing medium. If your roof allows more extensive growth, you can add a separate growth layer over the drainage layer. This is often called a semi-extensive green roof and can support more varieties of vegetation including prairie flowers, bulbs, and grasses.
  5. Structure. Be sure that you understand structural issues before embarking on planting a green roof garden. The last thing you want is your roof to fall in on you! If you do not have expertise in carpentry or green rooftop gardening, consult a structural engineer or your local building inspector.  It is vital that you exercise caution while creating a beautiful rooftop garden.

Once you are finished with your green rooftop garden, consult your local building inspector so he or she can take a look at it. If you have a green roofing expert around, go ahead and contact him or her as well.  You want to know that your roof is structurally sound and that your rooftop garden will thrive.

Seametrics, a manufacturer of water flow meters that measure and conserve water.