Limitations of SPF roofing systems

Specifying SPF Roofing Systems: Part 4

What are the limitations of SPF roofing systems?
A relatively small crew can install large spray polyurethane foam (SPF) roofing systems like those from Conklin, but it requires a high degree of technical knowledge and experience. Many courses are available from suppliers and from the Spray Polyurethane Foam Alliance (SPFA) to shorten the learning curve.

When incorrectly installed, SPF roofing systems often exhibit interlaminar blistering of the SPF layers. Foam blisters most often occur by trying to stretch the application window, improper substrate preparation, or equipment problems.

SPF roofing systems, like most roofing systems, must be installed under suitable environmental conditions. The SPF applicator should not proceed with substrate temperature below the manufacturer’s recommendations or humidity within 5 degrees of dewpoint. In addition, SPF and the protective coating should not be applied when there is ice, frost, surface moisture, or visible dampness present on the surface to be covered. Barriers may be required if wind conditions can affect the foam quality or create overspray problems.

Since applicator knowledge and experience is important to the successful installation of a SPF roof, it is important to thoroughly investigate past performance when selecting a SPF contractor. Fortunately, the United States has high-quality foam contractors in every
geographic region.

SPF is spray-applied and is very lightweight. While the overspray outside of the zone of application typically does not pose a health hazard, it can stick to many surfaces from great distances away. Building owners and contractors should have an overspray protection plan in place before starting a project.

Some coatings can emit strong odors while curing. Curing may occur very quickly or over many hours. When installing a SPF roofing system, air-handling units should be turned off and covered if occupants are in the building. They should remain covered until the SPF is sprayed and the coating can cure.

SPF roofing systems vary widely in cost depending on the foam thickness required, the type and thickness of the coating or covering, the degree of substrate preparation, availability of contractors in a specific region, and other factors. As with other roofing systems, there are high-end and low-end SPF roofing systems. Michelsen Technologies performed a life-cycle analysis for SPF roofing systems in five climate areas of the United States. The study concluded that the average SPF roofing system in those areas cost between 15- and 50-percent less to install and maintain than conventional membrane systems over a 30-year time frame. The study reported costs based on 6-year, 10-year, and 15-year recoat schedules.

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