roofing
Green roofs are ‘low-maintenance’, not ‘no-maintenance’
G
reen roofs are designed so that they will not require endless hours spent on the roof in order to keep them looking at
their best. Each type of green roof brings many different benefits to the occupants, the owners and the roof itself, so a little time maintaining the system is advantageous in the long run. London is an excellent example of the rate of
living roof growth in the UK. Green roofs are sprouting up on new rental properties and council buildings all around the capital city. The reason for this is the space being lost due to this urbanisation – many developments are replacing green areas that are habitats for local wildlife and species of various plants, flowers and grasses. The ball is rolling to counter this through policies
suggesting that developments are now expected to incorporate living roofs where possible. This is a step closer to the policies in Germany that have been in place for many years, and to the recent law passed in France, stating that rooftops on new buildings in commercial zones must be partially covered in plants or solar panels. The Flood and Water Management Act 2010 will bring us much closer to that situation.
Types of roof maintenance
Further green roof maintenance processes differ depending on which system is installed on the roof. Sedum green roofs require very little
maintenance as they are very hardy plants and don’t require much attention to keep them healthy. A sedum green roof can be maintained easily in two visits, one in the spring and one in the autumn. In the spring, the gutters and drainage channels will be cleared, any weeds removed and fertiliser applied. Weeding is particularly easy on a sedum roof due to the lower level of substrate preventing many weeds from establishing, and those that have established are easily removed. In the autumn the drains can be checked again and the spent flower heads and
any weeds that have grown over the summer can be removed. With this little maintenance sedum will remain healthy and the green roof will stay looking lush throughout the year. Other systems require slightly different
maintenance. With wildflower roofs it is recommended that the year’s growth is cut back and removed in the autumn. This prevents a build-up of decaying organic matter on the roof and the nutrient levels do not get too high. Biodiverse roofs require little maintenance because they are designed to be seeded naturally by the local environment. Some housing associa- tions or private landlords prefer the removal of certain species from their biodiverse roofs and others like to cut back the year’s growth in autumn but this is personal preference and is not essential for biodiverse roofs.
The only other form of maintenance green roofs
need is irrigation. As green roofs only have a limited depth of substrate to reduce weight, moisture cannot be drawn up from deep in the ground like it can for conventional plants. That said, a good drainage board will allow the plants to absorb all the water they need to stay healthy using only natural precipitation. However, in the first few months after installation the plants will be ‘stressed’ from the move and will be trying to establish in a new environment. In this time, and in periods of extremely hot and dry weather, roofs may need irrigation in the form of full saturation once or twice a week.
Maintenance issues
Although the task of maintaining a green roof is usually straightforward, there are issues that may arise before a maintenance team reaches the roof. Access is often a stumbling block. When a
green roof is initially installed there is usually scaffold and easy access to roof level. Six months later when maintenance is required the building is completed and the scaffold has been removed. In order to meet health and safety requirements the green roof company would need a man-safe system or a scaffold tower to fulfil the works. Simple, consistent maintenance of living roofs
leads to less roofing headaches in the long term for housing associations, local authorities and private landlords. Keeping a green roof maintained prevents damage to the roof which can lead to expensive remedial works.
46 | HMM March 2016 |
www.housingmmonline.co.uk
Green roof maintenance is generally a very simple process as Tom Storrer, sales and marketing at Sky Garden Ltd explains
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