As I have said before in various blog posts, the roofing industry is well known for speaking in code. We use acronyms and other words to speak in code. For those on the outside of the industry looking in, it may be difficult to understand why certain terms are used. It is important to understand why these terms are used so that you can properly refer to a roofing system on your home or commercial building.
An example of a unique description of a roofing system is the term built-up roof. Many may refer to this type of roof system as a tar and gravel roof or an asphalt roof system. These are different terms and descriptors which apply to a traditional built-up roof system.
The term built-up roof describes how the system is constructed and installed. Built-up roof systems are comprised of multiple plies or layers of asphalt impregnated felts that are combined together using heated asphalt as an adhesive. Typical built-up roof systems incorporate either three or four plies into the finished roof membrane assembly, however there are installations that comprise less than three plies or more than four plies.
These multi-ply applications are installed by offsetting the plies as the installer progresses across the roof surface. For example, if the system is a three ply application the ply sheets will be offset by twelve inches so that there will be three plies at all locations on the roof system. As the contractor installs the roof they are building up the plies by installing each ply one at a time progressively across the roof. The contractor is building the roof membrane on site which is where the term built-up roof was established.
To finish a built-up roof system, installers will either install a glaze coating of asphalt over the finished membrane surface or they will install a gravel surfacing set in a flood coat of asphalt. Both options provide a weathering surface for the roof system to complete the installation.
Have you had to repair a built-up roof system? How did you go about finding the leak area in your built-up roof?
Photo © Jurin Roofing Services, Inc. Built-up roof system with gravel surface.