Flat Roof Drainage Detail

Alwitra flat roof details.

Flat roof drainage detail.

These drains are like the drain at the bottom of your shower except that the roof drain has a larger strainer to protect it from debris. When designing a roof it is essential to pay close attention to where the drains are. A major maintenance issue shared between all types of roof drains is debris removal. 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.

Watch for clogs blockage at the roof drain or scupper. Drains are responsible for removing water quickly and efficiently. Each of these systems has its own pros and cons. Download free high quality cad drawings blocks and details of roof drains organized by masterformat.

Having sufficient drainage on a flat roof is vital. A flat roof may use interior drains to collect water from the centre of the roof. A correctly build flat roof will drain the rainwater quickly and effectively into the gutters without allowing water to collect in depressions and pond on the surface of the roof leading to the build up of silt deposits on the roof and stresses in the membrane when the water freezes a small amount of ponding is inevitable and it should not reduce the performance of the roof covering. There are roof coating products available if there isn t enough slant or slope to accomplish this.

The drainage requirements for flat roofs on buildings present some special problems that we describe and illustrate here. On many occasions drains are too high and water cannot flow off. Keep in mind all flat roofs have a slope of between five and 15 degrees to allow water to flow into drain systems such as eaves drainage holes or outlets. Most of the time strainers that come installed with a drain are not well designed.

At page top and at left our photos show a low slope roof surrounded by a parapet. A gravity drainage system on a flat roof differs from the gutter system you find on residential roofs in two key ways. Details and technical drawings of the flat roof drainage as downloads in the practical pdf dxf and dwg formats. Some pipes are too small to handle the volume of the water.

There are three types of drain systems commonly used on flat roofs. Most flat roofs suffer from poor drain locations or drain levels that are high. Flat roof drain types. Of course the best designed flat roof has the correct amount of pitch to drain the water off naturally.

The one challenge with flat roofing is ensuring proper drainage. Roofs of this design will have one or more roof drains or scuppers installed.