Roof Drain Slope

Increasing the angle of a flat roof will always increase the speed of water movement across the surface.

Roof drain slope.

According to the chart for 1 8 slope per 12 of pipe for 5 000 square feet of roof area with a 6 per hour of rainfall the required pipe size is 8. Due to the gradual low slope of this type of roof rainfall will not drain as effectively. Since the pitch of the roof is lower it can act as a catch all for tree limbs and other debris. When the bubble on a level is about 1 4 of the way past the line it is about a 1 4 slope.

The roof pitch or slope factors for roof pitch are used to multiply or increase the rainfall rate if we are draining a sloped roof the roof drain or gutter or drain piping or downspout leader size diameter other size constraints e g. Use the longest level possible for your application for the best accuracy. To size the vertical roof drain for the same parameters 5 000 square feet of room area and 6 per hour of rain consult table 1106 2 figure 3. Care must be given so that debris does not collect and thus cause damage.

This may eventually cause leaks and other damage. The angle is not significant enough to prevent water from pooling on the surface. Roof drains for flat or low slope roofs come in a few standard types. Same logic with 1 8 slope 1 16 slope etc.