Flat Roof Parapet Drainage

To design a sloped or flat roof drainage system we need to know the anticipated maximum rainfall rate and the flat or projected roof area.

Flat roof parapet drainage. It s also sometimes used in tandem with scuppers. Inner roof drains are used on flat roofs and include a low section or channel that collects water and feeds it into a concealed drain that leads to an underground drainage system. 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. This kind of drainage system is most common on small flat roofs where water volume and buildup isn t extreme.

A minimal slope of is needed for water to drain off the roof properly to prevent buildup of water and leaks and other roof problems usually you are not seeing a flat roof but a parapet or wall that contains the flat roof. Inner drains are resistant to freezing but can require careful maintenance to prevent problems. The main benefit of inner drains is that the system is hidden from view. Drainage on a flat roof or nearly flat is very important.

Poor drainage can lead to serious issues with flat roofing from leaks to structural damage. Manually adjust roof planes to have a negative pitch to create a parapet wall structure with a center drain. The one challenge with flat roofing is ensuring proper drainage. For clarity flat roofs actually have a slight slope to allow rain water to drain off the roof but they seem flat when compared with more traditional steeply sloped roofs.

The slope should be a minimum of 1 in 80 but in practice a minimum slope of 1 to 40 should be used to allow for deflection of the roof and for normal building tolerances. Flat roof drainage. 6 24 2014 david howard aia said.