Flat Green Roof Drainage

The greenslope roof ponding repair kit provides a lightweight inexpensive solution to flat roof ponding.

Flat green roof drainage.

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. Modular green roofs are installed differently than layered green roofs requiring a different style of roof drain. For flat or nearly flat roofs primary drains are located at the lowest point of the roof. If stone ballast is being utilized around the drain the 84 option shown above.

Flow of water into them is promoted by positive drainage. Along with the benefits of a flat roof come unique challenges. Your building and location can help determine which drain will fit your roof needs. Ponding water on flat roofs reduces the roof s lifespan.

Poor drainage can lead to serious issues with flat roofing from leaks to structural damage. 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. 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. Secondary overflow drains are located at a higher point on the roof.

The most critical of these issues is the flat roof drainage systems. Increasing the angle of a flat roof will always increase the speed of water movement across the surface. The bottom edge lies flat against the roof to prevent rooftop penetration. The build up of a flat green roof will vary depending upon the intended use.

Type of flat roof drainage each drainage low point roof sub area is allocated a roof drain and an overflow drain. Zurn offers a variety of roof drain solutions suited for modular green roofs such as the z163 and the 84 options both shown below. Grs drainage conduit is constructed from 80 recycled 16 gauge stainless steel. 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. A rooftop garden or additional outside living space are the top reasons people choose flat roofs. The one challenge with flat roofing is ensuring proper drainage. The drainage system of any roof can be located at the edge or in the middle of the roof.