Green roofs – roofing systems that incorporate living vegetation as part of the roof build-up – have moved from being a niche architectural statement to a mainstream requirement in London’s commercial and public sector building landscape.
Planning authorities across the capital increasingly require green or biodiverse roofing as a condition of development consent.
Housing associations, NHS trusts, and local authorities are incorporating them into refurbishment specifications in response to sustainability targets, biodiversity net gain requirements, and urban heat island mitigation policies.
At DL Jones Roofing Services, we deliver sustainable and green roofing solutions across London and the South East – integrated with our high-performance flat roofing systems to create installations that are both environmentally valuable and technically excellent.
This guide explains the different types of green roof, their benefits, the technical considerations involved, and who they are best suited to.
Types of Green Roof: Understanding the Options
Extensive green roofs
Extensive green roofs use a shallow growing medium – typically between 60 and 150 millimetres deep – planted with low-growing, drought-tolerant species such as sedum, mosses, grasses, and wildflowers.
The low substrate depth means the additional structural loading is relatively modest, making extensive systems suitable for a wide range of existing roof structures with appropriate engineering assessment.
Extensive green roofs are low-maintenance by design – the species chosen are selected for their resilience and ability to thrive with minimal intervention.
They do not typically support human access and are not designed as usable roof terraces. Their primary value is environmental: biodiversity support, stormwater attenuation, thermal performance improvement, and visual amenity.
They are the most commonly specified green roof type on schools, commercial buildings, and housing blocks across London.
Intensive green roofs
Intensive green roofs use a deeper growing medium – typically 200 millimetres or more – supporting a wider range of planting including shrubs, trees, and lawn areas.
They are designed to be accessible and usable, functioning as roof gardens, terraces, or amenity spaces.
The additional loading from an intensive system is significantly greater, requiring a purpose-designed or substantially reinforced structural frame.
They are most commonly found on new-build commercial developments and high-end residential schemes.
Biodiverse or brown roofs
Biodiverse or brown roofs are specifically designed to provide habitat for urban wildlife – particularly invertebrates and ground-nesting birds such as the black redstart and various bumblebee species.
Rather than using a uniform planting substrate, biodiverse roofs incorporate a varied surface – rubble, gravel, bare substrate, and sparse vegetation – that replicates the brownfield habitat that many urban species depend on.
They are increasingly specified by London planning authorities as a condition of development.
The Benefits of Green Roofing for London Buildings
Planning compliance and biodiversity net gain
The Environment Act 2021 introduced a mandatory requirement for ten per cent biodiversity net gain on most new development in England. Green and biodiverse roofing is one of the most straightforward ways of delivering measurable biodiversity units on urban development sites where ground-level planting opportunities are limited.
Working with an experienced roofing contractor who understands the biodiversity net gain calculation framework is essential for projects where planning compliance depends on demonstrating an adequate BNG uplift.
Stormwater management
Green roofs significantly reduce and delay the flow of rainwater from the roof into the drainage system.
An extensive sedum roof can retain between forty and ninety per cent of annual rainfall – reducing peak flow rates and relieving pressure on drainage infrastructure.
For buildings in areas with combined sewer overflow issues or drainage capacity constraints – which describes much of central and inner London – this attenuation benefit has real practical value.
Thermal performance and energy efficiency
The growing medium and vegetation layer of a green roof provide additional thermal mass and insulation value that improves the overall thermal performance of the roof build-up.
In summer, the evapotranspiration process of the plants has a cooling effect – reducing the urban heat island effect and lowering internal temperatures. In winter, the additional thermal mass reduces heat loss. For buildings seeking to improve their EPC rating or meet Part L compliance requirements, green roofing contributes meaningfully to the overall energy performance calculation.
Extended roof lifespan
The growing medium and vegetation layer of a green roof protect the waterproofing membrane beneath from the primary causes of premature degradation – UV radiation, thermal cycling, and physical damage.
Studies of green roof installations across northern Europe demonstrate that the waterproofing membrane beneath a green roof consistently outlasts an exposed membrane on a comparable building by a significant margin.
Technical Considerations for Green Roof Installation
Green roof installation requires specialist knowledge across roofing, waterproofing, structural engineering, drainage design, and horticulture.
At DL Jones, we deliver green and biodiverse roofing as integrated solutions – combining our expertise in flat roofing services with specialist green roof system suppliers. Every project begins with a thorough survey and structural assessment.
You can also explore our roof surveys and reports service to understand how we assess suitability before any green roof specification is prepared.
The waterproofing membrane specified must be root-resistant and of appropriate performance for a system that will be permanently covered and inaccessible for extended periods.
The drainage layer must be correctly specified to prevent waterlogging while retaining adequate moisture for the growing medium. And the substrate and planting specification must be appropriate for the aspect, exposure, and loading constraints of the specific roof.
Which Sectors Commission Green Roofing Most Frequently?
Green roofing is commissioned across a wide range of sectors. Local authorities often specify biodiverse roofs on new civic buildings to meet planning conditions. Housing associations incorporate extensive green roofs on flatted residential developments to improve sustainability credentials and EPC performance. And commercial properties increasingly use green roofs as part of their ESG reporting and BREEAM assessment submissions.
Discuss a green roof project: 020 8657 0734
