The roof is the most vulnerable place in the entire building, since it is it that is subjected to the greatest exposure to natural phenomena, rains, snow, temperature changes leave an indelible mark on the roof roof. For the most part, the building has a flat roof, therefore, an integral part of it, which protrudes to protect roofing coatings, comes out a drainage.
If a roof with a slope can independently get rid of water flows, then this cannot be said about a flat roof. She does not have the natural ways of excreting excess fluid, so she, like no other, needs a drainage.
Distinguish between internal and external drainage. The internal drainage is located inside the building itself in some distance from the walls and consists of water intake funnels, a riser, diverts and release. This system should ensure water drainage from the roof, regardless of the outer air temperature. Hence the water enters the rain sewage network. Funnels are located on the longitudinal side of the roof.
The external structure is more practical. It implies the collection of flowing water from the slope of the roof and takes it along special gutters to the sewage pipes.