What is a Green Roof?
A green roof is a roof that is covered in plants to reduce the flow-off of storm water and to increase the energy efficiency of a house. Green roofs are relatively simple to construct and works with any building that has a top that is more or less flat. They typically work best on roofs with slopes of around 20 – 30 degrees.
A green roof consists of a waterproofing membrane, a layer of soil, and vegetation. There are mainly two types of flat green roof: extensive green roofs and intensive green roofs. Extensive green roofs typically have a shallower layer of soil that works best for sedum or moss. Intensive green roofs, on the other hand, have a thicker layer of soil that can accommodate larger vegetation with deeper roots. In some cases, intensive green roofs may even have trees.
Weight is one of the most primary considerations when deciding whether you should construct a green roof. Your structure has to be able to carry the weight of all the vegetation as well as the water that it will absorb when it rains.
Make use of a survey to ensure that your weight-bearing walls, supporting structure and roof trusses can carry the load of the garden on your roof as well as the water. If you find that your supporting structure is too weak, consider an extensive garden or constructing the necessary reinforcements to increase the integrity of your roof structure.
Maintaining Your Green Roof
It is important to remember that a green roof is just like a regular garden that has to be maintained. Make sure that you have complete and safe access to your green roof to allow you to get rid of weeds and add fertilizer.
If you prefer a low-maintenance garden, consider an extensive garden rather than an intensive one as the bulk of green roof maintenance concerns the soil layer.
Components of a Green Roof
A green roof mainly consists of a number of layers. If your roof is completely flat, the first layer is a protection board. Over the protection board comes an ethylene propylene diene monomer waterproof membrane, which is a rubbery material. This membrane also prevents plant roots from entering your home.
To spread the rainwater that reaches your roof evenly and to prevent the soil from washing away, you can also add a filter layer, a drainage layer, and a water retention layer. On top of these layers is the growing medium, which consists of porous material and soil. The thickness of this layer depends on whether you have an intensive or extensive green roof.
Vegetation forms the top layer. Intensive gardens work well with shrubs and grass and, for extensive gardens, consider sedum roof systems.
What is a Sedum Roof System?
A sedum roof system is a popular extensive green roof system that is typically grown at a nursery and added as a complete unit to your roof.
Adding sedum roof systems may be the easiest way of turning your roof into a green roof. It consists of a pre-grown mat of fully grown sedum plants that contains a wide variety of species that is green throughout the entire year. A sedum roof system is typically shade and drought tolerant and requires minimal maintenance.
Sedum roof systems are lightweight and nurseries or other providers grow them specifically for roofs. With these extensive green roof systems, you don’t have to grow your green roof plants from scratch and you don’t have to experiment with different lightweight growing medium types. All the work is done for you.