Drainage

Green Roof Solutions offers many different drainage layer options, depending on system goals regarding water retention. The most critical role of the drainage layer is to provide an adequate flow of water off the roof during and after rainfall. The design of the different drainage layers allows for a portion of the stormwater to be retained above where the water is allowed to flow freely off of the roof. The systems are designed to ensure that stormwater can be used by plants for longer periods of time without oversaturation of the system. This promotes plant growth, avoids anaerobic soil conditions, and keeps retained water from pooling on the roof.

GRS drainage products typically fit into a green roof system above the GRS Root Barrier and below the GRS filter fabric. Depending on regional precipitation rates and the water retention goals for your specific project, Green Roof Solutions has a full range of products to meet your needs.

Filter Fabric

Beneath the growing media and above the drainage system, the filter fabric keeps the media from clogging up the drainage while allowing water to flow freely. Green Roof Solutions has a 3.5-oz filter fabric, FF35. An important consideration with filter fabric is the promotion of the flow rate while preventing media runoff. The GRS FF35 has a high flow rate of 150 gallons per minute per square foot. The FF35 is a fabric composed of virgin polypropylene staple fibers that are randomly arranged and needle-punched to form a cohesive geotextile. GRS filter fabric is resistant to UV degradation and biological and chemical environments found in soil.

Drainage Panels

GR32 / GR52

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Green Roof Solutions GR32 and GR52 drainage panels come in 24″ x 24″ interlocking squares constructed of 100% recycled high-density polypropylene (HDPP). The GRS GR52 panel size is 24″ x 24″ x 2.125″. The GR52 can withstand 0.352 gallons per square foot, or 1.4 gallons per panel. When dry, the weight of the panels is 0.855 lb. per square foot, or 3.42 lb. per panel. With water, the weight of the panels is 3.79 lb. per square foot, or 14.81 lb. per panel.

The GRS GR32 panel size is 24″ x 24″ x 1.25″. The GR52 can withstand 0.165 gallons per square foot, or 0.66 gallons per panel. When dry, the weight of the panels is 0.6 lb. per square foot, or 2.4 lb. per panel. With water, the weight of the panels is 1.93 lb. per square foot, or 7.72 lb. per panel.

GRS1.5

The GRS1.5 is a three-dimensional molded plastic sheet measuring 40″ x 48″ x 1.5″. The GRS1.5 panels are easily cut to fit around rooftop penetrations, perimeters, and drains. The GRS1.5 can withstand 0.078 gallons per square foot, or 1.04 gallons per panel. When dry, the weight of the panels is 0.26 lb. per square foot, or 3.5 lb. per panel. With water, the weight of the panels is 0.91 lb. per square foot, or 12.18 lb. per panel. The flow rate is 23.5 gallons per minute per foot.

Geodrein

The Green Roof Solutions Geodrein is a high compressive strength molded plastic panel measuring 19.7″ x 19.7″ x 2.36″. The GRS Geodrein has integral, alternating wing joints that snap the panels together during installation. The GRS Geodrein can withstand 0.142 gallons per square foot, or 0.382 gallons per panel. When dry, the weight of the panels is 0.82 lb. per square foot, or 2.2 lb. per panel. With water, the weight of the panels is 2 lb. per square foot, or 5.4 lb. per panel. These panels are ideal for intensive gardens, and they provide a stable base for built elements in the garden such as paving and built-in place walls.

Drainage Cores

Green Roof Solutions’ drainage cores are hybrid products that primarily allow for drainage, and aid in filtration and water retention, depending on the product.

Extenduct / Extenduct 2

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GRS Extenduct is a 40% recycled drainage core in a waffle pattern with a geocomposite fabric bonded to the top side. The design creates an open and continuous flow path, even under high loads. The filter fabric top layer prevents clogging from the growing media, and the waffle entanglements sit directly on the root barrier.

GRS Extenduct 2 includes an additional geocomposite fabric bonded to the bottom side that lies against the root barrier for added protection.

Aggredrain and Drainage Conduit

Aggredrain is a lightweight aggregate drainage layer constructed of rotary-kiln expanded clay aggregate and/or expanded shale. Aggredrain is most commonly used at a 1″ minimum depth over a moisture retention mat, GRS MRM 14, or GRS MRM 30. A filter fabric layer on top should separate the Aggredrain from the growing media.

The Green Roof Solutions drainage conduit is a stainless steel channel for use with the Aggredrain system. The 6″ slotted triangle shape is used beneath the Aggredrain layer and allows for water to flow freely. The channel is designed to be laid end-to-end and terminates either in the ballasted, unplanted roof area, or adjacent to the GRS inspection chamber-covered roof drain. The bottom edge lies flat against the roof to prevent rooftop penetration. GRS drainage conduit is constructed from 80% recycled 16-gauge stainless steel.