Asphalt built up is the most common form of roofing used for low sloped roofs (2:12) in America, constituting a large percentage of the overall number of roofs in the United States. Asphalt built up refers to several layers of reinforcing felt between asphalt and plies, or coal tar bitumen, which are covered with a surfacing material that serves as a ballast and holds them down, also reflecting UV rays. Usually the surfacing material used is gravel, and for this reason it is sometimes also called “tar and gravel roofing”. There are, however, other kinds of built up roofs, including smooth Asphalt built up, and Ballasted Asphalt built up. Depending on weather conditions, the average life span of asphalt built up roofs is approximately 10-20 years.
A built up roof requires annual inspections, as it is very common to find several leaks that have developed over the year. Additionally, penetrations on an asphalt built up roof such as vents, pipes, and ductwork, require repairing and inspection once annually, as they may gradually open and require periodic re-sealing. Seams and flashings may also need some repair work, and delaminations and blisters may also needs to but cut off and fixed before they develop into leaks. For all asphalt built up related services, Roof 101 has an expert on hand for all kinds of applications.
Although they can be prevented if detected early, there are many frequently occurring problems during the life of an asphalt built up roof. The most common is leaks, because asphalt built up is so sensitive to penetrations. Alligatoring and blistering are also regular, as pockets of air and moisture may lie between layers of the asphalt built up.
As you're probably already aware, the roof on your house or building is more than just a layer of sheathing - it's a complex structure that is made of many integrated parts, such as insulation and guttering, which together make up one operative unit that protects your home against weathering.