Roof Slope Water Drainage

Slope for drainage is that there be no ponding water on the roof 48 hours after a rain during conditions conducive to drying many building codes have a slope requirement for membrane roof systems.

Roof slope water drainage.

Problems often result if you don t have enough internal drains. International building code 2012 edition ibc 2012 section 1507 require ments for roof coverings states all membrane roof. 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. Again it s best to check with a roofing professional about this.

Roof leveling compounds for deeper ponding areas tapered insulation can be used to filled the area and then the filler material can be applied atop to fine tune it. Designing a flat roof for runoff how water runs off a roof depends on the amount of rainfall and how quickly it needs to drain. Roof surfaces with a slope of at least inch per foot 1 19 toward points of free drainage need not be considered a susceptible bay the phrase toward points of free drainage is critical because it gives meaning to what is meant by a slope of inch per foot. Roof leveling compounds can help level these areas to their original install slope to facilitate water drainage.

A common slope used that covers most materials is 2 12 which means that for every foot the roof steps up or down 2 inches. When the roof surface has less of a slope water drainage tends to be slow so the potential of water intrusion increases since there is a greater potential for water to backup under the roofing material. For flat roofs the minimum recommended roof slope is 1 8 per 1 foot to accommodate rainwater drainage. On a large flat roof internal drains are essential since the roof slope can t possibly direct all of the water to the roof s edges to drain through the scuppers and into the gutters and downspouts.

However the minimum slope as per the international building code for standard flat roofs made from asphalt or tar is 1 4 per 1 foot. The slope is barely noticeable to the naked eye. In most cases if you were to eyeball a roof you would not notice that there is a slope. Therefore each type of roofing material has a minimum slope requirement that must be maintained to decrease the potential of water intrusion.