The coating system may serve other functions as well, such as resistance to mechanical abrasion and fire. A polyurethane foam roof is spray applied as a liquid to the substrate and chemically reacts in seconds and expands 20 to 30 times its original volume to form a strong monolithic waterproof layer of roofing. Water cannot run laterally through the system, a common problem with systems that are not fully adhered and have seams. If a leak does occur it is easier to locate. A typical SPF roof will weigh 0.5 to 0.7 pounds per square foot, much lighter than Built-Up or Single Ply systems.
Polyurethane foam has the highest efficiency of any commercially available insulating material.
Most SPF roof applications will return their investment in 3 to 8 years in lower heating and cooling costs. SPF roofing can be applied faster with fewer people than most other systems. It is less likely that the roofing project will be interrupted by bad weather and will result in a shorter period of disruption for the customer. A requirements for fire tests of roof coverings and meet the most severe wind uplift requirements. The energy efficiency of SPF roofs results in lower consumption of fossil fuels.