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Spray polyurethane foam roofing, commonly called SPF roofing, combines closed-cell spray polyurethane foam with a protective roof coating. The foam is sprayed directly onto the prepared roof surface, where it expands to create a continuous insulation and waterproofing layer. The finished foam is then protected with a roof coating system.

Unlike a conventional roof membrane made from separate sheets, an SPF roof is formed in place. The foam can create a seamless surface and can be tapered to help direct water toward drains and other designed drainage points.

Where SPF Roofing Makes Sense

SPF roofing is primarily a commercial and industrial roofing application. It can be used on a variety of structurally sound roof substrates when the existing assembly is suitable for the system.

• Commercial and industrial buildings
• Low-slope and flat roof assemblies
• Metal roof systems
• Existing roofs that are suitable for restoration
• New construction roof assemblies
• Roofs where added insulation and air sealing are valuable

The SPF Roofing System

A spray foam roof is more than just spray foam. The complete system includes the roof substrate, closed-cell polyurethane foam, detailing at seams and penetrations, and a protective coating. Each component has to work together to produce a durable roof assembly.

• Roof preparation and evaluation
• Closed-cell spray polyurethane foam
• Detailing of penetrations, drains, curbs, seams and transitions
• Protective acrylic or silicone coating
• Ongoing inspection and maintenance of the finished coating system

Closed-cell SPF provides both insulation and a water-resistant layer as part of the roofing assembly. It adheres to the prepared substrate and expands in place, allowing the system to cover irregular surfaces and create a continuous layer.

Because the foam is installed in place, it can also be tapered to improve drainage. Proper roof drainage is critical to the performance of the finished system, and existing moisture or damaged areas must be addressed before the foam and coating are installed.

Acrylic Roof Coatings

Acrylic coatings are one of the protective topcoat options used over spray polyurethane foam. They protect from weathering and ultraviolet exposure and can provide a highly reflective finished surface.

Acrylic coatings are water-based products commonly used in SPF roofing systems. They are available in different formulations and should be applied at the thickness and coverage required by the specific roofing system.

• Protects the foam from UV exposure and weathering
• Provides a reflective roof surface in qualifying colors
• Can be applied in multiple coats as required by the system
• Used as part of a complete SPF roofing assembly rather than as a stand-alone substitute for the foam

Silicone Roof Coatings

Silicone is another major coating option for SPF roofing. Silicone coatings form a flexible, monolithic membrane over the foam and are particularly useful where resistance to ponding water is an important consideration. 

Silicone coatings protect against weathering and ultraviolet exposure and can be spray-applied, rolled or brushed depending on the product and application.

• Excellent resistance to ponding water
• Strong UV and weather protection
• Flexible coating that accommodates roof movement
• Can be used over new or existing SPF when the substrate and coating system are approved
• Available in high-solids and other formulations depending on the project

The coating is an important part of an SPF roofing system, and acrylic and silicone are not simply interchangeable paints. The appropriate coating depends on the roof, drainage conditions, substrate, project specifications, and the requirements of the selected roofing system.

• Acrylic is often selected for reflectivity, weather protection, and a water-based coating system
• Silicone is especially valuable where ponding-water resistance is a major concern
• The roof must be properly prepared before either coating is installed
• The coating must be applied at the specified coverage and dry-film thickness for the selected system

SPF roofing should never be installed over a roof simply because the existing roof is still in place. The substrate must be evaluated and properly prepared. The roof should have positive drainage, and areas containing trapped moisture or damaged materials need to be addressed before the SPF system is installed.

• Clean and properly prepared substrate
• Positive drainage
• Removal or repair of wet and damaged areas
• Proper treatment of penetrations, drains, curbs, and other details
• Adhesion testing when required for existing coated roofs

Restoration Without a Full Tear-Off

When an existing roof is structurally sound and suitable for an SPF restoration system, spray foam roofing can provide an alternative to completely removing the existing roof. The system can add insulation, create a seamless weather-resistant surface, and extend the service life of a roof when properly designed, installed, and maintained.

Whether SPF restoration is appropriate depends on the existing roof assembly and its condition. A roof evaluation should be completed before determining whether restoration or replacement is the better option.

Built as a Complete Roofing System

SPF roofing is not simply spraying foam on a roof and painting it. The finished roof depends on proper preparation, foam application, detailing, coating selection, and coating thickness. ISO approaches SPF roofing as a complete system so the finished roof is designed to perform as a roof, not just as insulation.

If you are considering spray foam roofing for a commercial, industrial, or other qualifying building, contact ISO to discuss the existing roof, the building, and the goals for the project. We can evaluate the application and determine whether an SPF roofing system is a good fit