Three Ways to Create A Green Roof

5 min read

edgings for green roofs

Create a green roof – 04.08.23 – Architects, property developers and householders are all looking for ways to improve eco-efficiency and combat the effects of climate change. The benefits of a green roof are huge, not only do they provide a habitat that supports the UK’s pollinators, but they are also quite easy to maintain and can look amazing.

Green roofs are a green solution that can support wildlife, improve insulation and add extra colour to your garden. Green roofing solutions include sedum kits for pitched and flat roofs as well as extensive blankets or ready-made trays.

Sedum Extensive Roof Blanket

Before doing anything…. Your roof must have a load bearing capacity of at least 150Kg per square metre to be able to cope with a green roof. This includes the weight of live loading – a person walking on the roof to install the green roof or carry out maintenance.

If in any doubt its worth seeking the advice of a structural engineer before undertaking an extensive green roof project.

To complete your green roof installation, you will also need the following:

  • Lightweight green roof substrate – the growing medium to sustain plant life.
  • Drainage board – A layer to control water by allowing just the right amount to be stored to sustain the sedum plants and allowing the excess to safely drain away.
  • Suitable edging – An edging not only improves the looks of the installation but ensures adequate drainage.

Sedum should flower between April and September (depending on local weather conditions). It will grow to around 150mm, but that can vary during the growing season. Sedum plants are perennial and frost hardy and can be installed at any time of year. Like all living plants the balance of plant species is affected by maintenance, pollinator populations and local climatic conditions.

When not in flower, the foliage of sedum plants are evergreen providing interest all year round.

One of the benefits of using a pre-populated sedum blanket is instant coverage. Plug plants can be time consuming to install and can take time to establish. If you are looking to increase biodiversity, use plug plants in conjunction with an extensive sedum roof blanket.


Flat Roofs:

If you have a sloping roof of 3 degrees or more then it’s not a flat roof.

On a flat roof use a root barrier to make sure the plants cannot damage your waterproofing. Next use a layer of specially engineered drainage mat to protect against damage to the roof or building. Green roof sedums dislike wet conditions. This matting ensures that excess water is wicked away from the roots.

Adopt a pre-grown green roof mat consisting of a carrier fleece for easy handling, specially formulated growing medium and of course, sedum plants.

Before you begin

Your roof must have a load bearing capacity of at least 120Kg per square.

Green roof build-up does not double as waterproofing. Ensure that your roof is fully waterproofed before adding your kit. After you have waterproofed your roof and made sure that it can withstand the necessary weight, you can begin to install your new flat green roof.

Drainage for every flat green roof should be efficient, to ensure that there is no excess moisture and water build up. If rainwater sits in puddles on your roof for any length of time, seek some professional advice before adding your green roof build-up.

Every green roof needs an edging to protect against wind uplift and dried out plants. You can purchase proprietary green roof edging; you can make it yourself or you can take advantage of an existing roof upstand.

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Pitched Roofs:

Sedum green roof kits are designed for use on roofs with a slope of 3 – 20 degrees.

More than just a fad or decorative novelty, a living green roof provides insulation. They can help prevent flooding, filter pollutants from the air, absorb noise and provide food and shelter for a variety of wildlife.

For sedum roofs with a pitch of 10 degrees or more, install an irrigation system and apply feed in early spring and early summer.

Sedum Roof Preparation

Please ensure that your roof is suitable for a sedum green roof. It must be able to carry a weight of 120kg per square metre without compromising the building structure. This figure includes ‘live loading’ – a coating of snow or a person walking on the roof.

Additionally, waterproofing needs to be in good condition, as a green roof build-up will make it more difficult to make repairs once the layers are in place.


Green Roof In A Tray

Green roof trays can be supplied full of sedum plants already to go, substrate included – as a completely self-contained green roof solution. Giving an instant green roof, quicker than matting alone delivering a rooftop transformation virtually overnight.

FLL compliant substrate is included – giving a completely self-contained green roof solution. So that means no planting or trying to work out how deep the growing medium needs to be. Just simply put down some roof protection and fix the trays in place.

Not only that but with roof edging holding everything in place, this is quite possibly the simplest and quickest way to create a green roof.

Where to start? Firstly, measure your roof, then work out the number of trays you need (they measure 500mm x 500mm) and calculate how much load your roof can cope with. Add in some roof protection fleece to protect your roof. Then, plan your delivery and put in place (carefully, the trays interlock too) and watch the transformation. Quick, convenient and green.

Before you begin

Your roof must have a load bearing capacity of at least 180Kg per square metre in order to install a green roof. Please note that this includes the weight of live loading – a person walking on the roof in order to install the green roof or carry out maintenance.

To complete your green roof installation, you will also need a fleece protection layer and some suitable edging, This will not only improve the looks of the installation but ensures adequate drainage.

Several choices, some simpler than others but hopefully not too daunting.


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