NBS Source
Extensive Green Roof - RoofDrain 25


For use in Green roof applications to prevent drying out or water logging of growing media during dry or wet periods. Below substrate layers 150 mm down including extensive and brown roofs.

It is particularly useful on pitched roofs due to the profile of the cone shaped cuspates.


ABG Roofdrain allows the storage of water within the cuspates of the of the HDPE core whilst facilitating the efficient drainage of any excess water away from the roof. This helps prevent the growing media from drying out during dry periods and from becoming waterlogged during wet periods. When used within a green roof construction it provides a versatile system for the collection of rain water at the base of the growing medium and for the prevention of water pressure on the structural waterproofing whilst allowing oxygen and nutrients to get to the roots of the plants.

Green Roof Intensive comprises:

- Growing media:

ABG peat free media derived from sustainable, 100% recycled, UK sourced materials. Using a specifically developed growing media can help provide the right growing environment for the selected vegetation and also reduce the load on the roof. The growing media can also be adjusted to support specific design requirements like calcareous applications

- Vegetation:

Specifically selected to suit the final finish requirements of the client/ end user. On Extensive green roofs low maintenance varieties such as mosses, herbaceous plants, sedums wildflowers and grasses tend to be used.

- Geotextile fibre fabric:

Laid beneath substrate to prevent fines filtering through to voids below.

- ABG Roofdrain:

Consists of three components bonded together to create a single element. A filter textile which is bonded to the upper part of the reservoir board to provide a separation layer which filters particles and fines down to 100 microns (µm) whilst preventing the substrate from any ingression into the reservoir layer.

A drainage/ reservoir board which attenuates and retains the optimal amount of water for the success of the plants and biodiversity of the roof, The core is perforated to allow the excess water to drain through into the flow channels beneath, preventing pooling and oversaturation of the plants. Finally, a protection fleece is bonded to the underside of the reservoir/ drainage board. It protects the waterproofing layer onto which the Roofdrain is placed.

Features and benefits:

  • Added protection for waterproofing layer.
  • Scores BREEAM points.
  • Reduces whole life costs of the building and its energy usages.
  • Part of SuDS solutions acting as the first stage in the treatment train.
  • Can create a useable space.
  • Creates a useable space.
  • Creates habitat to improve biodiversity.
  • Noise reducing.
  • Extracts pollutants and improves air quality.

General information




25 mm



Equal to the life of the green roof maintenance contract.

Uniclass 2015

Ss_45_40_47_28 Extensive green roof systemsPrimary


Q37/130 Extensive green roof

Specification data - Extensive green roof systems Enhanced data

Moisture control


Drainage layer

ABG RoofDrain 25.

25mm thick.

Reservoir capacity: 4.3 l/m².

Filter membrane

Filter textile bonded to the upper part of the reservoir board.

Moisture retention mat

Drainage/reservoir board.

Drainage ancillaries

Protection fleece bonded to the underside of the reservoir/drainage board.

Root barrier


Not required.

Digital objects

Platform Compatible Version Certified to




Revit 2017


Download now from NBS National BIM Library


Green Roof brochure

Green Roof brochure

Third party certifications

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