How Much Slope For A Flat Roof

In general the minimum slope for a flat roof is 1 0 but as stated earlier this is only possible in theory.

How much slope for a flat roof.

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. Most roof s have a pitch in the 4 12 to 9 12 range. The slope of your roof is the angle at which it inclines or declines. The table below shows common roof pitches and the equivalent grade degrees and radians for each.

Flat roofs which aren t perfectly flat require a small slope to allow for water runoff. This is the basis for calculating the angle which is approximately a 1 19 degree slope. 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.

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. Low pitched roofs are generally difficult to maintain and you need special materials to prevent leaks.