What could go wrong with a green roof? 5 points to consider for your project
Keziah Biggs
Green roofs are an excellent and natural addition to any property. From commercial buildings, airports, and schools, to car parks, offices and even our own homes, they provide a range of environmental and psychological benefits for the world.
But as beautiful and beneficial as green roofs can be, that doesn’t mean each project goes smoothly from start to finish.
Many factors go into creating a green roof, with each needing a thorough plan to ensure the project's long-term success.
So, to help those looking into their green roof opportunities, continue reading for what can go wrong (and how to avoid it).
1. Substrate depth
Substrate depth plays a huge part in the success of your green roof project. Get this right, and your plants will thrive, but an incorrect substrate level will quickly cause your plants to dry and shrivel, especially when open to the elements.
The correct level of depth will ultimately depend on the vegetation specified, so it’s essential to consider this.
Low-growing sedum will need a shallow, low-nutrient, free-draining substance, whilst Wildflowers will require a deeper substrate of around 100-150mm.
Herbaceous plants, shrubs and trees on intensive green roofs will require even greater depths of around 300-450mm+.
Essentially, you cannot afford to underestimate the importance of substrate levels. It can be the difference between a project failing and a long-term success.
2. Green roof irrigation
Proper irrigation enables green roofs to flourish, keeping vegetation healthy throughout their lifetime. But if the irrigation system isn’t set up or planned correctly, your green roof, whether extensive or intensive, will soon become unhealthy.
Extensive, semi-extensive, and biodiverse green roofs require irrigation for 6-9 months for establishment. At the same time, intensive green roofs will always require an irrigation system. This is due to intensive roofs needing deeper growing mediums and, therefore, higher irrigation maintenance, allowing for the growth of trees and shrubs.
In short, a lack of water supply is a big reason green roofs tend to fail. Ensure this is thoroughly planned, and avoid relying on manual watering procedures.
3. Maintenance and access
Whilst extensive green roofs require little maintenance, an annual visit to feed and remove any pernicious weeds is essential. Without this, weeds can seed, and the roof becomes contaminated.
But with any roof, regardless of the level of maintenance required and before you can develop a maintenance strategy, you must confirm one vital point. That is – are you able to access the green roof for maintenance?
Should this be an issue, you should reconsider. Failure is probable without a safe way to access your roof for its required maintenance.
4. Plant selection
The layout and selection of green roof plants can make or break your project. Choosing vegetation suitable for the local weather, expected rainfall and levels of the sun will give your green roof every reason to thrive.
Different species require different levels of sunlight, which directly affects a plant's optimum location. For example, your roof may experience intense sun without any means of protection from the shade, meaning a ‘thirsty’ plant may not be suitable in these conditions.
5. Roof drainage
Whilst intense levels of the sun can cause issues for your green roof (species dependent), so can the contrary – rainfall. Rain can leave your green roof waterlogged when combined with insufficient roof drainage.
Impaired drainage is a common issue leading to plant loss, which usually happens when an unsuitable membrane has been used or wrongly installed. The drainage membrane allows water to drain away safely, protecting the roots of your green roof.
If this fails, plants will become waterlogged and die off.
So, it’s essential to ensure there are no blockages and that the membrane being used is sufficient.
Ensure green roof success with Future ECOsystems.
For more information on how we can help, or if you’d like to discuss your green roof project, contact our friendly team at Future ECOsystems today – we’re always happy to help and are standing by to answer any questions you have.