Green, Brown & Blue Roofs

We supply and install all forms of green, brown and blue roof systems from a number of the industry’s leading manufacturers and suppliers of specialist geosynthetic materials and green roof materials.

Cawston Specialist Roofing Ltd can offer a fully comprehensive package for green roofs; we can produce detailed specifications to suit each application to suit each application recommending suitable planting to suit the area and BREEAM (Building Research Establishment Environmental Assessment Method)

There are a number of Green/Brown Roof types available, but the most common are Extensive and Intensive systems.


The most common type of Green Roof, an extensive roof consists of a shallow substrate; typically 20-200mm deep and a variety of drought tolerant hardy plants/vegetation. An extensive roof is also referred to as a wild flower or sedum roof. Extensive roofs are relatively self-sufficient and are not designed and constructed with the intention of being trafficked by pedestrians. Therefore access to the roof tends to be limited other than for occasional maintenance.


An intensive Green Roof can be as simplistic or as complex as the client desires. Intensive roofs consist of a deep soil layer; typically 150-1500mm. Due to this soil depth there is greater scope of planting available. The roof can be viewed very much like a traditional garden area and can be landscaped accordingly to include tress, lawns, flower beds and paved areas. An intensive roof is also referred to as a roof garden or living roof. An intensive roof requires the same level of care and attention as any traditional garden.


A term commonly used to refer to a roof where the vegetation is intended to replicate the existing brownfield habitat. This type of roof can be seeded like the intensive or extensive roofs, or allowed to self-colonise; seeding increases the bio-diversity potential of the roof in the short term.

The Blue Roof System

A blue roof provides storm water attenuation capacity at source within the green, ballasted or paved roof, or podium deck construction of a development.

It comprises a combined drainage and attenuation void within the roof structure and a series of roof restriction chambers which sit over each roof outlet. The chambers are designed to release the attenuated water at a controlled discharge rate as permitted in the planning consent of the site.

Designing a blue roof in this way allows storage capacities suitable for up to a one in 100 year storm event, plus an allowance (typically 30%) for the effects of climate change, to be achieved. The water is filtered several times as it passes through the system removing suspended solids thus improving the quality of water at discharge. This stored water, as with a ‘traditional’ storage system, can be released at a controlled rate or even used as grey water or irrigation for the vegetation across the development.

The Blue roof system consists of two key components:

– A drainage geocomposite system with integral filter geotextiles which attenuates excess water not absorbed by the vegetation in soft landscape areas, or run off from ballast or paving, in hard landscaped areas. Water filters through the green roof and builds up in to the drainage void formed by the geocomposite layers below.

– This water is gradually dispersed through the zero falls system to the restrictor chamber and discharged to the roof outlet at the rate permitted for the site. The storm water attenuation requirements are met within the roof construction; therefore the need for underground storage can often be reduced/eliminated.

Features and Benefits: 

– Controlled storage and release of stormwater in line with SuDS best practice/ legislation.

– Reduction in roof penetrations and rain water outlets (RWO’s) required.

– Overall time and cost savings versus traditional methods.

– Removal of excavated material.

– Less disruption on site.

– Often no need to install underground attenuation tanks.

– Reduced carbon footprint.

– Zero fall; no need to screed to fall.

– SuDS schemes; provides source control.

– Contributes to the BREEAM rating and Code for Sustainable Homes.

– Improves quality of discharged stormwater.

It can be utilised beneath many types of finish including intensive and biodiverse green roofs, ballasted roofs and beneath paved surfaces at both roof and podium levels.