How To Slope A Flat Roof

Water that stays on a flat roof after it rains will weaken the material over time.

How to slope a flat roof.

There are two ways we typically use to create low slope on flat roofs. What is the most appropriate angle for flat roofing. Some sources consider low slope to include 3 12 pitch roofs. In general the minimum slope for a flat roof is 1 0 but as stated earlier this is only possible in theory.

Normally 1 80 0 72 is the recommended minimum angle for a slope and this is universal across the vast majority of flat roofing systems regardless of the materials that they incorporate. Creating a positive slope roof is traditionally done by installing rigid board insulation such as xps or polyiso on flat or low sloped roofs. If asphalt shingles are to be installed on a low slope roof special steps are required to avoid short roof life and roof leaks. The second is to slope the roof trusses themselves this is done by the truss manufacturer.

Xps and polyiso are available in boards that are no more than a few inches thick. Generally such roofs have a pitch ranging from 1 2 12 to 2 12. Eventually water penetrates the building. To put it in perspective the angle of this slope would be around 30 degrees.

Using modern cement screed mixes a professional flat roofer can fill dips and hollows quickly and level them or slope them rather to fill the low point and re create the surface of your roof. Low slope roofs are from 0 to 3 12 in pitch. 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. An example for a steep sloped roof is 8 12.

Flat roofs which aren t perfectly flat require a small slope to allow for water runoff. The first is using tapered foam insulation on top of the roof trusses. There is a problem with using these materials though. The second is usually the easier and cheaper solution although the foam insulation adds some additional r value.

Low pitched roofs are generally difficult to maintain and you need special materials to prevent leaks. Notes to the table above. This means that the rise of the slope goes up or down 8 inches for every 12 inches. This solution is perfect for homeowners looking for the easy option for adding slope to a flat roof property.

However in some cases building owners hire contractors that poorly designed the roof.