Green Roofing

About Green Roofing

What is green roofing?

Green roofing, also called a living roof, means covering a building’s roof with a waterproofing membrane and a layer of vegetation. It turns unused roof space into a growing surface that gives back several practical benefits: extra insulation, slower rainwater run-off and habitat for birds, bees and other wildlife. Green roofs suit a wide range of residential, commercial and public sector buildings across the UK.

Types of green roof for UK projects

The right system for a building depends on its load-bearing capacity, how much ongoing maintenance is practical, and whether the roof needs to be usable space.

Extensive green roofs

Extensive systems use a shallow substrate, typically 60-150mm deep, so they suit existing structures with limited load-bearing capacity such as garages, sheds and commercial buildings. They are usually planted with drought-tolerant sedum, mosses and wildflowers, and need little irrigation or maintenance once established, which makes them a practical option where low upkeep matters.

Intensive green roofs

Intensive systems use a deeper substrate, typically 150mm to over 1000mm deep, and can support a wider range of planting including grasses, perennials, shrubs and even trees. They need regular irrigation and maintenance, much like a conventional garden, and are usually designed for public access on new builds or structures with enough load-bearing capacity to carry a roof garden or park.

Biodiverse green roofs

Biodiverse green roofs can be extensive or intensive. They combine native UK plant species, varied substrate depths and features such as log piles and sand patches to attract a wider range of invertebrates, birds and pollinators. They are often specified to support urban biodiversity and to contribute to local Biodiversity Net Gain (BNG) targets.

Benefits of green roofing for UK properties

• Supports native UK pollinators such as bees and butterflies, along with birds and other urban wildlife, helping offset habitat loss in built up areas.
• Plants filter airborne pollutants and absorb carbon dioxide, which can improve local air quality.
• Green roofs absorb less solar radiation than conventional roofs, helping to cool buildings and reduce the urban heat island effect.
• The substrate and vegetation absorb and slow rainwater run-off, easing pressure on drainage systems and reducing flood risk during heavy rain.
• The extra build-up provides insulation, which can reduce heating and cooling costs.
• The vegetation layer shields the waterproofing membrane from UV light and temperature swings, which can substantially extend the working life of the roof.
• The layers also absorb sound, giving some acoustic benefit in noisy urban settings.
• A well planted roof creates a calmer outlook that can support occupant wellbeing and add to property value.
• Green roofs can contribute to BREEAM ratings and help meet planning conditions for sustainable development.

How a green roof is built

A green roof is built up in layers over the structural roof deck:

1. A root-resistant waterproofing membrane protects the building structure.
2. A root barrier stops plant roots penetrating the waterproofing.
3. A protection layer, often a geotextile fleece, guards the layers below from damage.
4. A drainage layer manages water run-off and aeration, using dimpled sheets or aggregate.
5. A filter fleece stops fine substrate particles washing into the drainage layer.
6. The substrate, a lightweight growing medium formulated for green roofs, supplies nutrients and water retention. Its depth depends on the type of roof.
7. Vegetation, whether sedum mats, plugs, seed or a mix of the three, forms the living surface.

To discuss which green roof system suits your building, contact Phoenix Amenity Supplies or use the enquiry form above.