What is an Intensive Green Roof?

An intensive green roof, also known as a rooftop garden or a high-profile green roof, is a type of green roof system designed to support a diverse range of vegetation, including trees, shrubs, perennials, and even lawns. 

Unlike extensive green roofs, which have shallow substrate layers and low-maintenance vegetation, intensive green roofs have deeper soil profiles, typically ranging from 6 to 24 inches (15 to 60 centimetres), which can accommodate a wider variety of plant species.

Intensive green roofs are more similar to traditional gardens and landscapes, with a greater emphasis on aesthetics and recreational use. 

The deeper soil allows for a more extensive root system, enabling the growth of larger plants, including small trees and shrubs. This creates a more lush and diverse green space resembling a traditional garden setting.

Due to the deeper soil and more complex vegetation, intensive green roofs require more maintenance and irrigation than extensive green roofs. They often incorporate irrigation systems and regular pruning and trimming and may require regular fertilisation and pest control. Access to the roof may also be necessary for maintenance activities.

Intensive green roofs offer several benefits beyond those provided by extensive green roofs. They provide increased stormwater retention and absorption capacity, contribute to better air quality and noise reduction, offer more habitat opportunities for wildlife, and can create inviting spaces for human use, such as rooftop gardens or recreational areas. They can also help with energy efficiency by providing additional insulation for the building.

However, due to the additional weight and maintenance requirements, intensive green roofs are typically more expensive to install and maintain than extensive green roofs. They are often implemented on larger buildings, such as commercial or institutional structures, where the added benefits and aesthetic value justify the investment.

In summary, intensive green roofs are characterised by deeper soil profiles and a wider variety of plant species, offering greater design flexibility, recreational opportunities, and ecological benefits but requiring more maintenance and investment than extensive green roofs.