Getting it right through design

There are fundamental principals that apply to the design of a green roof, regardless of the proposed landscaping, location or climate. The specified solution must replicate nature within the build up and be able to support the vegetation.

The first step - What is the landscaping finish to look like?

The primary decision is the type of landscape required that best suits the rationale behind the development, whether it is an intensive, simple intensive, extensive or biodiversity roof. Whatever the landscape chosen, the plants will have some basic requirements to sustain them; nutrients, a balance between moisture and drainage to suit the vegetation, and aeration to the root systems.

The next step - Planning the green roof to meet the needs of the vegetation

Once the vegetation finish has been determined the structural and design considerations and green roof components can be proposed.

  • Waterproofing system, structural loading and wind uplift
    The structural design of the building will embrace the specification of the appropriate waterproofing system to meet the demands placed on it by the green roof and the effects of climate, especially with regard to performance against high-wind.  More detailed information 
  • Falls and drainage
    How a green roof holds water for the vegetation whilst also allowing for appropriate levels of drainage is important when looking to reduce levels of rainwater run-off.  More detailed information 
  • Configuration of green roof components
    The selection of components to balance water storage and drainage of excess rainwater is, to a certain extent, dictated by the vegetation finish selected for the green roof.  Insufficent water storage means that either additional irrigation may be required or the vegetation will struggle to flourish.  More detailed information 
  • Perimeters and vegetation barriers
    Perimeter details have minimum requirements to comply with building regulations and vegetation barriers have important functions, one of them being to act as a fire break.  More detailed information 
  • Irrigation, maintenance and safe access
    Every green roof will require access for maintenance and in the case of intensive green roofs access is continual.  All access on green roofs should be safe for the user.  More detailed information 

Designing to protect the building's construction and flat roof waterproofing is vital when delivering a green roof as many additional forces can affect the structure.  Green roofs are installed on roof pitches ranging from 1° to around 30°. Fundamentally it’s about finding the balance between requirements for water storage, drainage and irrigation; sufficient depth of growing medium to support the intended vegetation and weight loading levels; as well as meeting the regulatory needs for construction, fire, safe access and the duty for maintenance.

Download our useful Green Roof Design Considerations guide. Download Green Roof Design Considerations brochure