Green roof information

Green roofs can be designed to include recreational space or to create habitat for wildlife.  The aim of the green roof is to replicate the ecosystem services (i.e. the benefits that people derive from nature) and ecological requirements of the local area. 

The GRO Green Roof Code of Best Practice for the UK 2021 is a code of practice created by industry stakeholders and contains detailed information on all aspects of green roofs.  The code can be found on The GRO Code of Best Practice 2021 | Green Roof Organisation

Swansea's Green Infrastructure Strategy Swansea Central Area - Regenerating Our City for Wellbeing and Wildlife recommends that only GRO Code compliant green roofs are installed in the Swansea Central Area. 

There are two main types of green roofs: 

1.    Intensive green roof - Intensive green roofs or roof gardens are designed principally as recreational or amenity space like a garden or park.  Greening can include lawns perennials shrubs and trees and substrate depth is deeper than that on extensive green roofs.

2.    Extensive green roof - extensive green roofs are primarily designed to absorb water and to create a habitat for wildlife.  Extensive green roofs include sedums, mosses, grasses and wildflowers, and have a minimum substrate depth of 80mm.  Extensive green roofs are designed to be low maintenance and can be very biodiverse.  Biosolar green roofs are extensive green roof with integrated photovoltaics.

Whilst a sedum mat green roof is an extensive green roof, sedum mats tend to offer minimal water retention benefits and can be vulnerable to drying out and failure.  Sedum mats without substrate beneath and certain other light weight systems are not GRO Code compliant and are not advised. The inclusion of native sedum species as part of a biodiverse extensive green roof is acceptable.

How do green roofs support the objectives of the strategy?

Green roofs provide numerous ecosystem services and therefore benefits to wellbeing and wildlife.  They contribute considerably to all of Swansea's five principles of GI, and can be a key solution to addressing surface water run off. 

Species selection for green roofs

Increasing biodiversity and creating a green artery through the Swansea Central Area to link the adjacent wildlife corridors and create connections for wildlife is the core aim of the strategy. Planting schemes should specify native species or species with a demonstrated biodiversity value for local wildlife creating 'buzz highways' or 'B-lines', shelter and food for wildlife.  Species should be suitable for exposed and dry conditions, the local environment and proximity to the bay and its associated coastal microclimate. Advice from qualified ecologists and landscape architects on species choice is recommended.

GRO code provides information on vegetation under Section 3.1.7.  Plants with a demonstrated biodiversity value can be found on the Royal Horticultural Society Plants for Pollinators document at www.rhs.org.uk/science/pdf/conservation-and-biodiversity/wildlife/plants-for-pollinators-garden-plants.pdf   The habitats created should be designed to support the local ecology i.e. plants, birds animals and invertebrates and can include log piles, sand piles, bee hotels etc. 

Green Roofs and the Green Space Factor Tool

Swansea's Green Space Factor (GSF) tool (Appendix 3 of the Strategy) assesses the quality and functionality of GI.  The range of ecosystem services provided by green roofs means that intensive and extensive green roofs (excluding sedum mat / light weight systems) carry high GSF scores.

Design, specification and maintenance

The Strategy expects that only GRO Code compliant green roofs are installed in the Swansea Central Area.  The GRO Code provides detailed advice and information on the design and specification of green roofs, including; configuration, structural design, water proofing, drainage, fire, irrigation along with a list of relevant complimentary documentation. 

When designing a green roof consider maintenance requirements and how that maintenance will be carried out. The GRO Code provides detailed advice and information on maintenance requirements. 

 Useful resources 

Swansea Central Area: Regenerating our City for Wellbeing and Wildlife - Swansea - Swansea's GI Strategy

Creating-Green-Roofs-for-Invertebrates_Best-practice-guidance.pdf (buglife.org.uk)

B-Lines | Buglife - Organisation devoted to the conservation of all invertebrates. 

www.livingroofs.org.uk - Living Roofs are the UK's leading independent living roof website which provides news research and the latest innovations in green roof and wall technology. 

Plants for Pollinators advice and downloadable lists / RHS Gardening  - Royal Horticultural Society: use the plants for pollinators filter at this link to view the selection of plants

Local case studies:

Swansea Environment Centre: An extensive green roof was installed in at the Environment Centre in March 2021 by The Urban Greening Company, funded by a Local Nature Partnership grant.  The green roof was planted and sown with 48 locally grown native wildflowers by Celtic Wildflowers and Environment Centre staff.

Coastal Offices High Street - A semi-intensive green roof was installed by The Urban Greening Company on the Coastal Office building High Street in March 2021, funded by the Welsh Government's Transforming Towns Green Infrastructure Grant. Designed to bring coastal habitat into the city the green roof is a really good example of creating a city centre space for people and nature.