Low Slope Roof Construction 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.

Low slope roof construction details.

The roof assembly is defined as the roof deck along with the roof membrane and roof insulation. Roof assemblies with a pitch slope of less than 3 12 are considered low slope roofs. These panels generally come with a painted mill finish or a clear acrylic finish. 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.

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. 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. Roof penetrations should be kept to a minimum and should be located within the flat of the panel where possible as opposed to near seams. 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.

Problems at these points typically arise from improper application methods and the use of inappropriate or incompatible materials. The most critical application points on low slope roof systems are at flashings penetrations and accessories. 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. Low slope roofs are often referred to as flat roofs.