SPF roofs are usually composed of a polyurethane foam, sprayed from a pressurized gun, and an elastomeric acrylic coating. Once sprayed, the foam forms a solid, seamless membrane that waterproofs and insulates.
These roofs need to be maintained on a regular basis and are not as common in hot areas, such as the southwest, because UV rays from sunlight cause the foam to crack and become brittle. SPF roofs are also highly susceptible to hail, bird, and insect damage.
Every 10-15 years, these roofs should be cleaned and re-coated. If installed and maintained properly, an SPF roof can last as long as 50 years.