April 11th

The Bailey Green Roofing Guide

Green roofs are soaring in popularity across the UK, crowning a growing number of commercial and residential projects, not to mention schools and public buildings. As land continues to be urbanised, green roofs allow built-up areas to reintroduce green spaces while reducing the negative impact of overdevelopment, thanks to the environmental, economic and social benefits associated with them.
It’s no surprise, with our focus on sustainable building solutions (including our Eco-Roof system), that we’re big fans of the green roof here at Bailey. That’s why we’ve created this quick and easy guide to green roofs and their benefits.


A green roof is a system that uses vegetation for the roof covering instead of just the weathering materials. This living layer sits on top of the conventional waterproofing layer of the building.
The use of vegetation in construction dates back thousands of years, however it recent times that they have once again become a popular alternative to traditional roof finishes due to their eco-credentials and significant cost savings on heating and cooling.
While green roofs come in many different forms and types, usually a distinction is made between extensive, intensive and biodiverse (brown) roofs. The main difference being the depth and thicknesses of the individual layers.
Each type of green/brown roof requires the following components:
• Protection fleece
• Drainage/reservoir layer
• Filter fleece
• Growing medium or crushed aggregate
• Planting/vegetation
• Hard landscaping and other components as necessary
Green roof systems can either be installed on new build projects in conjunction with root proof membranes or retrofitted to existing roof coverings by first laying a root barrier membrane.


Intensive systems typically involve the creation of a garden at roof level with the planting of shrubs, trees and grassed areas. As well as planting, intensive green roofs may incorporate hard landscaping, decking and paving, making the space into an appealing, useable area for residents or visitors to the building.
Due to the type of plants and vegetation used, a greater depth of substrate is required to support them and sustain growth. After installation, ongoing maintenance is required and the plants will need regular watering and feeding to ensure full establishment.


Extensive green roofs are planted for aesthetic and ecological reasons with vegetation such as sedum (succulents), mosses, herbs and grasses. This type of green roof requires little maintenance making it very economical, while providing a colourful, attractive roof covering that changes throughout the seasons. The plants used are wind, frost and drought resistant in order to survive in the tough, exposed conditions experienced at roof level.


Biodiverse (brown) roofs are designed to replicate the environment lost to development and can involve creating natural habitats for various species of plants and birds. Other debris, soil and items of stone and timber may be incorporated to replicate the desired environment.


Green roof systems offer many advantages to both the specifier and the client. Apart from introducing a creative dimension to the flat roof project, a green roof provides a whole host of financial and environmental benefits.
Durable and long lasting – waterproofing materials are protected from corrosive UV rays and large/extreme fluctuations in temperature throughout the day, increasing the life expectancy of the roof and reducing whole life costs.
Reduces heating and cooling costs – improves the thermal properties of the building, which also reduces CO2 emissions.
Increases property value – in 2011 New York the rents of apartments with green roofs were 16% higher than those without in the surrounding area.
Reduces air pollution and improves air quality – studies have shown that they can lead to a 37% reduction of sulfur dioxide and 21% reduction of nitrous acid above a green roof.
Reduces heat in urban areas – absorbs heat and allows evaporation of water. According to the Environmental Protection Agency, the annual air temperature of a city with 1 million people can be 1–3 degrees Celsius warmer than its surroundings.
Reduces flood risk – green roofs can retain 40-90% of rainwater they receive, reducing run-off and improving water quality (60% of cadmium, copper and lead, plus 16% of zinc can be removed from rainwater.)
Reduces noise pollution both externally and internally – green roofs act as sound insulation barriers. It is said that noise travelling from inside a building can be reduced by up to 40 decibels before reaching outside.
Aesthetically pleasing design – can help the building blend in with nature, or bring life to urban areas. They can also improve wellbeing and quality of those living and working in close proximity, especially in terms of creating accessible roofs into spaces for social or leisure activity.
Provides a natural habitat – green roofs can become a home for displaced flora and fauna
The green roof you choose will be dependent on building type and usage, climate, substrate depth and roof build-up. Whatever the specification, Bailey can supply the ‘complete’ system together with expert advice, assistance and recommendations. Bailey Eco-Roof Systems come complete with a whole range of components and accessories and a wide variety of plants. Contact us today to find out more.