June 18, 2024


The Gods Made Home

Do Flat Roofs Need to Be Sloped?

All flat roofs, despite their name, should have a slight angle to allow water to flow off the EPDM membrane and into a drainage system. This slope doesn’t need to be steep and can be nearly invisible, especially when the roof covers a large area.

What is the ideal angle for flat roofing?

The recommended minimum slope angle for all flat roofing systems, regardless of the materials used, is 1:80 (0.720). However, when installing a flat roofing system, it is advisable to aim for a slope angle of 1:40 (1.440). This accounts for material deflection and surface deviations.

What are the main sloping systems in use?

The slope angles of flat roofs are determined by the type of drainage system installed. There are three drainage systems that influence the slope of a flat roof:

  • Scupper Drains: These drains are installed at the end of the parapet wall, resulting in the flat roof being angled in both directions.
  • Internal Drainage: This type of drain is typically installed in the middle of the roof and carries water underneath the roof to a nearby sewer. The flat roof will have a slope towards the center on all four sides.
  • Gutter Mounted: If there is only one slope, the gutter and downspouts will be installed at the lower end of the roof.

This post was written by Ted Williams! Ted is the owner of A Old Time Roofing which is the premier roofing company that offers St Petersburg roofing contractor! Ted is a Master Elite Weather Stopper GAF Roofing Contractor, a double award winner of Best Steep-Slope Contractor from GAF and achiever of Master Elite Consumer Protection Excellence from GAF. He has been serving the Pinellas County area since 1978. Old Time Roofing has a tradition of quality workmanship, servicing residential and commercial properties.