How Much Slope For A Flat Roof

This is the basis for calculating the angle which is approximately a 1 19 degree slope.

How much slope for a flat roof. The table below shows common roof pitches and the equivalent grade degrees and radians for each. A pitch over 9 12 is considered a steep slope roof between 2 12 and 4 12 is considered a low slope roof and less than 2 12 is considered a flat roof. Despite the name all flat roofs need to be slightly angled in some direction. If you imagine the top of a building to be the base of a triangle and the peak of the roof to be the triangle s highest point the slope of the roof is the line that connects them together.

Flat roofs which aren t perfectly flat require a small slope to allow for water runoff. In general the minimum slope for a flat roof is 1 0 but as stated earlier this is only possible in theory. Generally such roofs have a pitch ranging from 1 2 12 to 2 12. The slope of your roof is the angle at which it inclines or declines.

It takes the manufacturer s recommendations the unique conditions of the roof as well as the skills and the expertise of the installer to arrive at the right slope. According to the international building code the typical built up flat roof that uses tar or asphalt goes by the guideline that for every foot 12 inches of a flat roof a minimum of inch must step up or down.