Flat Roof Roof Drainage Plan

It is very critical to position drains for maximum effect.

Flat roof roof drainage plan. On flat or low slope roofs that drain to one end lower right in the sketch especially if the building rear wall does not include a projecting eave or soffit a clogged gutter or downspout send water down the building rear wall flooding the structure through its wall or through windows. A flat roof will often have a parapet or false wall sur. 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. As water flows to the edge a metal diverter is usually placed at the eave to prevent dripping at walkways.

There are three types of drain systems on a flat roof. 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. Sented on the roof plan. Green roof solutions gr32 and gr52 drainage panels come in 24 x 24 interlocking squares constructed of 100 recycled high density polypropylene hdpp.

A major maintenance issue shared between all types of roof drains is debris removal. There are roof coating products available if there isn t enough slant or slope to accomplish this. A pitch of 1 4 per foot 2 percent slope is often used to help prevent wa ter from ponding on the roof. The result is the number of drains needed.

Determine 100 year 1 hour rainfall rate used for location of building. Most draining systems on flat roofs have a poor design or are not correctly installed. Of course the best designed flat roof has the correct amount of pitch to drain the water off naturally. Often the flat roof has a slight pitch in the rafters.

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. So often we find that inner drains are high on the roof causing water to pool around them. 50 000 4 400 11 36. The gr52 can withstand 0 352 gallons per square foot or 1 4 gallons per panel.

Poor drainage can lead to serious issues with flat roofing from leaks to structural damage. 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. Each of these systems has its own pros and cons. There are three types of drain systems commonly used on flat roofs.

The one challenge with flat roofing is ensuring proper drainage. Your building and location can help determine which drain will fit your roof needs. Or 12 drains required. The grs gr52 panel size is 24 x 24 x 2 125.

Size horizontal storm drainage piping. Take the roof s total square footage and divide by the total square footage handled by one drain.