Built Up Roof Membrane
A built-up roof (Smooth Built-Up, Ballasted Built-Up, or Tar and Gravel) is a class of low-slope roof that consist of laying down several layers of tar and water resistant materials and then covered with gravel. Many old buildings with low slope or flat roofs are topped with built-up roofing made from layers of asphalt-coated roofing felt. The top layer is usually covered with rock or gravel, which serves as a ballast to hold the roofing material down and protect it from UV damage. Built-Up Roofs with gravel surfacing are also known as Tar and Gravel roofs. The typical life span of a built-up roof is 10 to 20 years depending on weather conditions.
Types of Built-Up Roofing
How Long Do Built-Up Roofs Last?
The service life of a roof is dependent on many factors: geographical location & weather conditions, foot traffic, materials used, conditions under which the roof was installed, slope of roof, type of surfacing material, etc. Under ideal conditions, a 3-ply built-up roof should last at least fifteen years, a 4-ply should last at least 20 years, and a 5-ply should last at least 25 years. This author has seen ten year old 4-ply roof that needed to be replaced and twenty year old 3-ply roofs that were still functioning.