The following roof coverings are commonly used for low-slope roofs. These roofs are considered to be water impermeable or weather proof. Low-Slope roof membranes consist of three components; a weatherproofing layer, reinforcing layer and surfacing. Roofs installed at a 3/12 pitch or less are considered to be “low slope.”
Single-Ply membranes, while newer to the market, have had very good results over the last ten years. TPO & PVC are the most widely used “white” membranes, while EPDM is the most widely known “Rubber Roof.” Many of these membranes have natural elastic properties, low-VOC install options are available, and higher energy efficiency (sans EPDM). They have multiple installation options that can fit most scenarios and budgets.
Modified Bitumen (Mod-Bit) roofs are made from a mixture of bitumen, modifiers and solvents. The rubber provides a “thermoplastic elastomer” that will melt and help bond the membrane/reinforcement to the substrate. These roofs require a UV reflective surface and do not tolerate standing water well.
Built-up roofs are some of the most time-tested roofs on the market. They are composed of bitumen (asphalt) and, primarily, fiberglass felt plies. The asphalt is typically hot-applied, however cold-applied asphalt systems are now available. When properly installed and maintained, it can be an excellent waterproofing system.
Elastomeric Coatings are excellent in the proper situations but are rarely used as a primary source of moisture mitigation. They can provide a membrane that bonds to the structural concrete substrate for a vegetative roof. They may also be used to extend the lifetime of the system that is currently on the roof, if properly installed. Once cured, they create a monolithic membrane.
Sprayed Polyurethane Foam is a very unique type of roof system and requires a skilled installer. Similar to Elastomeric Coatings, they are typically not used as a primary membrane. SPF is typically used as an alternative to removing and replacing the current roof system.