Low Slope Roof Drainage

Proper drainage cannot be emphasized enough when discussing or reviewing the requirements of any well drained low slope commercial roof system figure 1.

Low slope roof drainage.

Typically though there is a steel beam at the low point which prevents the installation of the roof drain at the low point. The building in figure 2 is located in the mid atlantic region near a large city on the east coast. One of the most common we see is the lack of proper drainage. The building was unoccupied at the time of a cursory audit.

On a flat roof you don t get the same slope so the water has nowhere to go. 4 x 5 downspout scupper box scupper with sleeve closed top scupper with sleeve open top 7 gutter shop fab gutter more search low slope. Consequently the roof drains must be located on the plumbing drawings up slope from the low point. Here at boak sons our commercial roofing repair technicians are experts in spotting potential problem areas on low slope roofs.

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. The asphalt roofing manufacturers association arma recommends that roof designs provide adequate slope minimum of inch per foot to ensure that the roof drains freely throughout the life of the building and to thereby avoid the effects of ponding water. A traditional roof on a home is slanted. Through building drains upper right in the sketch become clogged internally and burst flooding the building or leaks occur around the drain itself where it penetrates the roof.

Prudent designers would like the roof drains to be located at the low point of the structurally sloped roof deck.