Low Slope Roof Construction Details

The most critical application points on low slope roof systems are at flashings penetrations and accessories.

Low slope roof construction details.

By low slope roofing we mean any roof that is pitched at less than 4 inches of rise in 12 inches of run or 4 12 pitch. If the upper edge of a low slope shed roof intersects a vertical wall the most logical approach in my opinion is to detail the roof as an unvented roof. Roof assemblies with a pitch slope of less than 3 12 are considered low slope roofs. The roof system is defined as the roof membrane including surfacing and the roof insulation.

Low slope structural roofing generally used on roof pitches ranging from 12 to 3 12 consists of interlocking panels commonly called standing seam roofing that run vertically along the roof surface. Generic valley treatment details for metal panel roofs for low slope with and without substrates are included in the mbma metal roofing systems design manual chapter 12 metal roof details. Another approach is to build a cupola or ventilated doghouse in the middle of the low slope roof an approach championed by joe lstiburek. Regular asphalt shingles and standard skylights will work at pitches of 4 12 or greater but at lower pitches you have to use different materials.

Low slope roofs are often referred to as flat roofs. These panels generally come with a painted mill finish or a clear acrylic finish. These critical junctures account for the majority of roof leaks. Problems at these points typically arise from improper application methods and the use of inappropriate or incompatible materials.