Green roofs offer a variety of benefits, from aesthetic to environmental. Sedum and moss roofs create a living patchwork of colours, providing a soft-textured carpet that changes with the seasons. They help insulate your home, reduce rainwater runoff and support local wildlife.
However, while green roofs are often described as low-maintenance, this does not mean that they are maintenance-free. Neglect can quickly lead to bare patches, invasive weeds, blocked drains and even damage to the waterproofing beneath the roof.
Our step-by-step guide to green roof maintenance, packed with advice from industry experts, will help you keep your green roof looking great and performing at its best.
1. The first maintenance step is getting the design right
“Although green roofs generally need very little maintenance, neglect can lead to all sorts of issues," warns Dusty Gedge, international ambassador for the European Federation of Green Roof and Wall Associations. “All too often designers or customers opt for the lightest and the thinnest systems which actually require more care.”
Instead, Dusty advises homeowners to install deeper, heavier systems that can survive short droughts and support a greater variety of plants. “Sedums only flower in late May and June, while the various species of wildflowers can bloom from April through to October. Extensive garden-like roofs allow for a more biodiverse mix of native wildflowers and sedums,” he says.
Grass should also be avoided on extensive green roofs as it is heavily reliant on water. “Designers often want that natural ‘cultural’ aesthetic of a meadow, but this is best avoided because irrigation will be an absolute necessity,” Dusty warns.
Dusty Gedge is an international ambassador for the European Federation of Green Roof & Wall Associations, an organisation that is committed to creating more healthy environments through using vegetation on roofs and walls.
2. Keep on top of your weeding
Regular hand-pulling weeds is the safest way to protect your green roof. Invasive species should be targeted early, before they establish deep roots.
Plants such as Buddleia are a common issue. “Its root structure is pretty invasive and so we like to keep these under control, generally by hand pulling,” says Mike Cottage, sustainability director at The Urban Greening Company.
“If they get out of control, professional stem injection may be required. Any other species that may be too dominant are hand pulled.”
“When removing wind-borne weeds such as Buddleia and Fleabane take extra care to avoid damaging the waterproofing layer,” adds Gary Grant, technical director at The Green Infrastructure Consultancy.
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Mike is sustainability director at The Urban Greening Company, a firm specialising in green roofs, walls and bringing urban biodiversity to our homes and towns
Gary is a founding director of the Green Infrastructure Consultancy, and leads the company's technical team, supporting clients across all projects. He has also worked on large-scale projects such as the Queen Elizabeth Olympic Park
3. Make sure drainage is clear
Clear gutters and drains are essential to ensure water flows off the roof efficiently. Gravel firebreaks should also be cleaned regularly to prevent weed growth and fire hazards.
“If the gutters or drains fail, the roof could fail. Silt and detritus can be removed by hand,” says Chris Roddick, product manager at Bauder.
Chris is a Product Manager at Bauder, a company specialising in providing materials and solutions for flat roofs. Chris works on projects that deal with the company's provision of green and blue roofs
4. Use the correct feeding and watering schedules
Most extensive green roofs require minimal fertilisation. “Some firms recommend slow-release fertiliser pellets, but in my experience, these are rarely necessary. Sedums, mosses and drought-tolerant wildflowers generally thrive on what’s naturally available in the substrate,” says Chris Roddick.
Beyond feeding, water management as part of your green roof maintenance is another key factor in keeping your green roof healthy. Sedum is very drought tolerant but global warming means that they will require irrigation in dry periods.
The bigger issue is access. “An inaccessible roof is likely to fail over time,” warns Chris, and while irrigation is possible with the use of sprinklers they use a lot of water. The thickness of the growing medium also plays a crucial role in plant survival during hot summers and heavy rain.
“With hotter summers and heavier rain it is also so important to ensure that the green roof has a substrate (growing medium) of at least 80mm plus vegetation, or at least 100mm if seeded,” adds Gary Grant.
5. Deal with bare patches
However, even with appropriate feeding and watering, occasional plant losses or overcrowding can create bare patches or monocultures that need attention. Generally they should be filled.
“Pick leaf and cuttings from the adjacent areas and sprinkle over the bare area, or peel off sedum and soil from new sedum blankets and lay these onto the area,” suggests Mike Cottage.
More serious problems such as erosion, wind lift and substrate damage can occur and cause patches, but these issues are only common on houses. However if these problems do occur, Mike says that the remedy is to, “patch the bare areas and often add large 40-60mm (or bigger) pebbles to create more long term stability.”
Reflection from glass facades can also create dead zones where the vegetation burns off. The fix in this situation is once again to cover the affected area with pebbles.
Patches may also appear as a result of pest infestations and diseases, including fungal moss, rot or aphid infestations. But, experts say these these are uncommon and more likely to occur on damp roofs, or where airflow is restricted.
6. Don't be afraid to deadhead, thin and trim
“For most green roofs the vegetation is allowed to colonise and spread naturally, but roofs are hostile environments and not all plants will survive,” notes Chris Roddick. Overcrowding is uncommon and if certain species try to dominate they can be thinned or removed by hand-pulling. This may also be necessary to manage monocultures, and removing coarse grass or clover will also help to promote biodiversity.
Regular trimming and deadheading will remove dead growth, encourages new vigour, and prevents any one species from dominating. Seasonal growth should be monitored, and removal of straggly plants is advised.
“We tend to do this between October and February," says Mike Cottage. "However, it needs to be done selectively. In particular we leave anything that is flowering. Plants with hollow stems also provide winter refuge for a lot of invertebrates, so we would leave these as well,” he notes.
7. Get a regular professional inspection
Professional inspections identify issues noted throughout this guide such as blocked drains, substrate erosion, or damage to the mesh and other materials. Catching emerging problems early, protects both vegetation health and the overall longevity of the green roof.
While the vegetation itself should be checked by a qualified professional once or twice a year, maintenance of a green roof is not however required to maintain insulation or the waterproofing, notes Gary Grant. “The green roof actually protects the waterproofing from the elements and extends the life."
Considering a green roof as part of your self build or extension plans? Be inspired by this dream extension that included a green roof, hidden wine cellar and skylight nook. Or, if you are looking to create an even 'greener' home, check out the advice in our guide to eco-homes.
