How does a green roof work?

Posted on by Protech Roofing Team

It’s time to turn climate change around by working with the world, not against it. This month we’re here to provide you with all you need to know about green roofing, so you understand the significant benefits of an eco-roof, how it works and why they’re increasing in popularity.

What is green roofing?

Instead of using materials such as cement, plastic and metal, a green roof is made using a waterproof membrane topped with soil and vegetation. In between these layers you will find root barriers, drainage and irrigation systems all to maintain a fully functioning roof.

How does it work?

Generally green roofs are installed on flat surfaces, but can be installed on roofs with a  20-30 degree slope. There are different types of green roofs including extensive and intensive roofs.

  • Extensive roof – A thin layer of soil with shallow, smaller rooted plants like moss, for example.

  • Intensive roof – A thicker layer of soil made to support large plants with bigger roots and sometimes even trees.

Before your green roof is installed, a survey must take place to ensure that your roof will be able to withstand the weight of a garden and excess water from a heavy downpour. If your roof needs extra support there are options available to satisfy all health and safety regulations.  

The basics

  • If you have a flat roof, there will be a protective board placed over the top of your existing roof.
  • Next, a waterproof membrane will be layered on top. This layer has a rubbery consistency similar to the lining of a duck or fish pond. This stops water from seeping through the roof and prevents roots from growing deep into the protective board.
  • If you wish for another layer of insulation on top of your roof this can be placed over the waterproof membrane.
  • The drainage and irrigation systems will also be installed to help distribute the rainfall evenly to ensure a healthy, green garden. This will also act as a natural solvent to keep the soil in place and prevent it from being washed away.
  • Above this there will be the ‘growing medium’. This will be compacted with soil and organic, aggregate materials including sand and fine gravel. This combination is engineered to be as light as possible to ensure it’s ideal for a rooftop and promote the growth of various plants.
  • Lastly, seeds will be sown and plants will be planted. Just remember, if you want bigger plants it’s important that you invest in an intensive roof. An extensive roof is for a simple sedum finish and requires little maintenance.


  • Reduced bills – an eco roof will provide your home with increased insulation; perfect for the winter and also helps to keep the home cool during long hot summers.
  • Increased house value – adding a green roof is not only an aesthetic addition to your home, it can also add up to 20% extra to the home’s value.
  • Positive state of mind – knowing that you are contributing to protecting the environment can vastly improve your wellbeing. An attractive garden may also encourage neighbours to invest in their own eco-roof.
  • Air filtration – rain collects unwanted particles along the way, such as dust and bacteria. However when droplets land on the plants, these particles will be captured by the leaves and collected into the soil rather than remaining in the air. This results in cleaner and fresher air when the water eventually evaporates, and a number of potential benefits for your respiratory system.  
  • Habitat for wildlife – your green roof will be the ideal for home for wildlife such as birds and butterflies.


Protech Roofing are here to help create a brighter and greener future for those eco-friendly households. With our wealth of experience you can guarantee a watertight and attractive roof garden at a price you can afford. If you would like to save on your energy bills and lower your carbon footprint, get in touch with our team of experts today and find out more!  

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