Flat Roof Drainage Design Guide

Poor drainage can lead to serious issues with flat roofing from leaks to structural damage.

Flat roof drainage design guide.

There are roof coating products available if there isn t enough slant or slope to accomplish this. Of course the best designed flat roof has the correct amount of pitch to drain the water off naturally. Drainage devices e g sizes elevations type of material inlet and outlet structures energy dissipators. Unless otherwise recommended by a geotechnical engineer lacrc.

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. The one challenge with flat roofing is ensuring proper drainage. When designing a roof it is essential to pay close attention to where the drains are. At page top and at left our photos show a low slope roof surrounded by a parapet.

Watch for clogs blockage at the roof drain or scupper. The flat roof drainage design guide can go up against different style that when nitty gritty right can ooze a cutting edge feel. Or 12 drains required. Determine 100 year 1 hour rainfall rate used for location of building.

Flat roof drain types. Take the roof s total square footage and divide by the total square footage handled by one drain. Having sufficient drainage on a flat roof is vital. It is a requirement of building regulation part h that adequate provision is made for rainwater to be carried from the roof of the building.

Main features flat roof drainage design guide first off the flat roof drainage design guide is an extremely basic direct and utilitarian design every single current trademark. Size vertical storm drainage piping. The most critical of these issues is the flat roof drainage systems. Size horizontal storm drainage piping.

Roofs of this design will have one or more roof drains or scuppers installed. Select number of roof drains and calculate the roof area sloped to each drain. The drainage requirements for flat roofs on buildings present some special problems that we describe and illustrate here. 50 000 4 400 11 36.

Most flat roofs suffer from poor drain locations or drain levels that are high. Some pipes are too small to handle the volume of the water. Show down spout and location of discharge to ground surface which shall be at least 5 feet from foundations walls or to an approved drainage system. Your building and location can help determine which drain will fit your roof needs.

Along with the benefits of a flat roof come unique challenges. According to bs 6229 bs 8217 flat roofs should be designed with minimum falls of 1 40 to ensure a finished fall of 1 80 can be achieved allowing for any inaccuracies in the construction. There are three types of drain systems commonly used on flat roofs. Ipc provides four steps to size the roof drains on a building.