There are several different types or classifications of low-slope roofing systems. Each system has its strengths and weaknesses and some may prove to be a better re-roof solution for a specific building than others. Please call us to discuss which roofing system will work best for your building.

Built-Up Roofing Systems

Built up roof membranes have been in use in the U.S. for more than 100 years. These roof systems are commonly referred to as “tar and gravel” roofs. BUR systems generally are composed of alternating layers of bitumen and reinforcing fabrics that create a finished membrane. The number of plies in a cross section is the number of plies on a roof: The term “four plies” denotes a four ply roof membrane construction. Sometimes, a base sheet, used as the bottommost ply, is mechanically fastened. Built up roofs generally are considered to be fully adhered if applied directly to roof decks or insulation. This has been the standard type of roofing system for many years and most likely to be the type of system that is on your current roof.

Roof Restoration Systems

Restoration Systems, also known as roof coatings, are a cold application process of roofing over an existing roof. They combine waterproofing grade asphalt (emulsion), polyester ply sheets and an energy efficient white acrylic-based elastomeric coating that conforms to California’s Title 24 Energy Efficient building code. The white acrylic coating can be substituted for a water-based aluminum coating but this will not conform with Title 24. These systems have become widely popular over the last decade for their energy efficient qualities and there low cost due to eliminating the need for tearing off old roofs.

Modified Bitumen Roofing Systems

Polymer-modified bitumen or modified bitumen (MB) sheet membranes have been in use in the U.S. since the mid 1970s. Polymer-modified roof membranes are composed of reinforcing fabrics that serve as carriers for the hot polymer-modified bitumen as it is manufactured into a roll material. MB roof system membranes are composed of multiple layers, much like BUR membranes. MB roof systems typically are installed as a two-ply system and almost always are fully adhered. This type of roofing system is usually used when a building shows signs of movement due to it’s flexible and almost “rubberized” quality.

There are two types of MB roofing membranes:

  • SBS polymer-modified bitumen membranes commonly are installed in hot moppings of asphalt (similar to BUR systems) or cold adhesive. Some SBS modified membranes are self adhering; that is, they contain an adhesive backing.
  • APP polymer-modified bitumen membranes typically are heat-welded or torch-applied.

Single-Ply Roofing Systems

Single-ply membranes are factory-manufactured sheet membranes. They generally are categorized as either thermoplastic or thermoset. Thermoplastic materials can be repeatedly softened when heated and hardened when cooled. Thermoset materials solidify, or “set,” irreversibly after heating. Single ply membranes commonly are referred to by their chemical acronyms such as TPO, PVC and EPDM. Single-ply membranes can be installed fully adhered, mechanically attached or held down with ballast. Most single-ply roof systems do not receive surfacings. These systems have become more and more popular over the last decade. Especially, in more recent years because of California’s Energy Efficient Title 24 Building code and their competitiveness with Built-Up Roofing due to rising oil prices.

West Coast Roofing Certifications