Identifying Commercial Roofing Systems
November 22nd, 2010
Built Up Roofs (BUR), Modified Bitumen (MB), and Single Ply Membranes Roofs are the three major types of commercial roofing systems. How can you identify the type of roofing system on a particular building? Most build up roofs include small gravel the size of your thumb nail or smaller, although a few can be smooth surfaces and include a coating. The distance between the sheets will range from approximately 8” to 17” apart depending upon how many plies have been used to make up the membrane. With four ply BUR’s the sheets should be approximately 8” apart. With three ply membranes the spacing should be 11”, and with two ply BUR’s the spacing should be 17”. Some BUR’s will be smooth surfaced and may include a coating but the easiest way to identify BUR systems is to look at the spacing between the sheets.
Modified Bitumen membranes are thicker and the sheets installed farther apart than conventional BURs. The distance between the seams in an MB roof should be 33”. Many MB roofs have a granule surface similar to the granules on a roofing shingle. Asphalt flow should typically be observed at the seams of these membranes.
Single Ply membranes are comprised of two major types of membranes. EPDM rubber is the predominate type of single ply. Thermoplastic membranes are the other types of single ply membranes. All EPDM roofs installed within the past 15 years should be black in color. White or gray membranes are typically thermoplastic. The sheet sizes of single ply membranes range from smaller sheets which would be 5’ wide to some that can be 100’ wide. There are three ways to install these roofs and they include ballasted, fully adhered, and mechanically fastened. Ballasted is the easiest to identify since the ballast for these roofs should be approximately 2” in diameter. Mechanically fastened single ply membranes can be one of several types. Older roofs of this type may have a plastic knob or multiple patches over fasteners within the field of the membrane. These are both visible on top of the membrane. Most newer single plies have the fasteners in the seams. These roofs may billow up on a windy day and/or you can move the membrane with your foot in the center of the panels. Finally fully adhered membranes will be smooth surfaced. Many Single Ply membranes are installed using this method. These membranes are typically adhered over a mechanically fastened insulation so the insulation fasteners may be visible under them membrane but they will not penetrate the membrane.
Identification using these factors will assist you when discussing your roofing system with others. There are reasons why certain roofing systems may deviate from these descriptions but the majority of roofing systems conform and can be identified with these techniques.
By kacey
Posted in: Roof Inspection, Roof Replacement Project, Roofing Specifications
This entry was posted on Monday, November 22nd, 2010 at 5:08 pm and is filed under Roof Inspection, Roof Replacement Project, Roofing Specifications. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.
