Building a green roof is a great idea. We have been talking about this for a few weeks now and will continue to do so.
Today we will take a look at the preparation stages of building a green roof – structure and roofing membrane to ensure that the base is watertight.
The benefits of building a green roof can be extensive, as we have discussed;
- Insulation properties
- Aesthetic qualities
- Water management possibilities
- Wildlife & environmental issues
To move forward, when building a green roof it is important to begin with the structure.
This must be sound, with no rot and good supports. You should calculate the weight of your roof, especially once waterlogged, to approximately 150kg per square meter. This is the average weight, so your structure should be super-strong!
You will need to look at the structure of your existing roof before you even consider building a green roof. Once the plants begin to establish themselves, you do not want to find that the structure is in danger of collapse.
Bring in a structural engineer or planner to help you to determine this. Bring in an independent surveyor and ask for a written report to ensure you can cover yourself with the planning and building regulators.
Once the structure is established as safe, you are ready to plan the roof itself. There are a good many layers that will need to be applied before the planting stage, so don’t rush out and buy the plants just yet.
If you, however, live on a rural property, you could begin harvesting tiny cuttings that are already indigenous and store them in a polytunnel or greenhouse/cold frame to bring them on.
Building a green roof involves planning and careful design and research to ensure it works!
Initially, the roof should be covered with a sound roofing membrane to ensure that it stays watertight for the duration of the roof. I recommend a fantastic rubber-based EPDM membrane by Firestone. With an expected lifespan of 50 years, and applied in one piece, it will provide the perfect cover for protection when building a green roof. The membrane can be applied with a water-based adhesive and easily cut to fit around protruding elements, such as vent chimneys or roof skylights.
Once applied, there will be no worries or concerns about internal leaking.
The next stage of our journey into building a green roof will discuss the next two layers of drainage materials and plant liners.
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