Liquid roof membranes consist of a one or two component resin that is applied over reinforcement material (typically polyester or fiberglass felt). This system can be applied over a variety of different substrates (modified bitumen, certain single ply membranes, B.U.R., concrete, or metal). It can be applied with squeegees, rollers, or sprayed. Once it has cured, it becomes seamless, UV-resistant, water-resistant, chemical-resistant, while also accommodating movement. Liquid membranes are also aesthetically pleasing, as they can come in a variety of colors.
The technology for the resin-based liquid-applied systems was developed in Europe in the mid-1980s and early 1990s. In the early 2000s, European standards were developed as the popularity of the liquid membranes was making in-roads in the roofing industry and more manufacturers were developing their systems and offering long-term warranties. When these membranes were first introduced in the United States, the drawbacks for these systems were that they were expensive, limited in supply, and extremely difficult to work with. As manufacturers began building factories in the United States, prices dropped significantly and supply became sufficient and as more contractors worked with the systems, labor prices began to drop