Flat Green Roof Drainage

Secondary overflow drains are located at a higher point on the roof.

Flat green roof drainage.

The bottom edge lies flat against the roof to prevent rooftop penetration. The drainage system of any roof can be located at the edge or in the middle of the roof. Your building and location can help determine which drain will fit your roof needs. Ponding water on flat roofs reduces the roof s lifespan.

There are several drainage options to repair pooling or ponding water on flat roofs including internal drains gutters and downspouts scuppers and roof leveling compounds. Grs drainage conduit is constructed from 80 recycled 16 gauge stainless steel. Zurn offers a variety of roof drain solutions suited for modular green roofs such as the z163 and the 84 options both shown below. Flow of water into them is promoted by positive drainage.

The greenslope roof ponding repair kit provides a lightweight inexpensive solution to flat roof ponding. The most critical of these issues is the flat roof drainage systems. Poor drainage can lead to serious issues with flat roofing from leaks to structural damage. 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.

If stone ballast is being utilized around the drain the 84 option shown above. The one challenge with flat roofing is ensuring proper drainage. The need for flat roof drainage in order to prevent water accumulation and moisture damage flat roofs need to be equipped with special drainage systems. For a large roof it is recommended to have drains placed at multiple locations within the area of the roof.

Along with the benefits of a flat roof come unique challenges. A standard roofing membrane and insulation layer is laid onto the underlying roof structure then a studded perforated drainage membrane such as oldroyd xv 20 greenxtra is used in addition to provide a drainage layer. Increasing the angle of a flat roof will always increase the speed of water movement across the surface. Unlike other roofing types that are slanted or sloped to allow water to drain automatically flat roofs need a built in drainage system to help remove moisture and debris.

A green roof may require a separately plumbed secondary drainage system also known as the overflow relief system. For flat or nearly flat roofs primary drains are located at the lowest point of the roof. Please contact our technical department on 01403 210204 or submit an enquiry for more information. Modular green roofs are installed differently than layered green roofs requiring a different style of roof drain.