Spray Foam Roofing Pros and Cons

Today’s blog post will be of interest to both building owners and roofing contractors. We discuss the pros and cons of a spray polyurethane foam roof and consider some of the installation factors that can affect its performance.

In previous posts, we have weighed the benefits of spray foam roofing and some common misconceptions about commercial spray foam roofing. Here, we take a closer look at the advantages and disadvantages of this roofing system from both the building owner’s and contractor’s perspectives.

Spray Foam Roofing System Components

A spray polyurethane foam (SPF) roofing system generally consists of a spray-applied foam layer protected by a compatible coating or other protective surfacing.

The exact assembly varies by manufacturer and project. Depending on the system, protective coatings may be applied in multiple coats, and reinforcement or additional detailing may be used at seams, penetrations, transitions, or other roof areas.

The performance of the finished roof depends on the condition and preparation of the existing substrate, proper foam application, protective coating thickness, drainage, weather conditions during installation, and ongoing maintenance.

Pros of Spray Foam Roofing

When properly designed, installed, and maintained, spray polyurethane foam roofing can offer several advantages:

• Provides roofing and insulation value in a single system
• Can reduce heat transfer through the roof assembly because of the insulation provided by the foam
• Can be combined with a reflective protective coating that reduces solar heat absorption
• Creates a continuous foam layer that conforms around penetrations, curbs, flashing, and other roof details
• Can be applied at varying thicknesses and, in properly designed applications, used to help improve roof slope or drainage
• May reduce tear-off when an existing roof is structurally sound and otherwise suitable for restoration
• Can be repaired and recoated when the existing SPF system remains in suitable condition

Actual energy performance depends on climate, insulation levels, building use, HVAC efficiency, roof construction, and other conditions. Likewise, service life depends on installation quality, coating protection, maintenance, climate, traffic, and other factors.

Cons of Spray Foam Roofing

There are also several contractor-facing challenges with a spray foam roof system. Building owners should understand these because proper application is especially important to the system’s performance.

• SPF requires specialized equipment and careful application according to manufacturer specifications
• Installer training and experience are important because improper proportioning, spraying, or surface preparation can lead to defects
• Weather conditions such as temperature, wind, humidity, and moisture can affect application
• The initial project cost may be higher than some other roofing or restoration options depending on the building and assembly
• The protective coating requires inspection and maintenance so that the foam remains protected from ultraviolet exposure and physical damage
• Removal can be more difficult than with some other roofing materials if the SPF system eventually needs to be replaced

The value of SPF roofing should therefore be evaluated based on the particular building rather than assuming that energy savings or other benefits will automatically offset the initial cost.

Things that Can Cause Spray Foam Roofing Failure

Several conditions can contribute to premature SPF roofing problems, including:

• Bird or animal damage
• Improper foam application
• Using foam that does not meet the requirements of the roofing system
• Application under unsuitable temperature, wind, moisture, or weather conditions
• Leaving spray polyurethane foam exposed to ultraviolet radiation
• Failing to apply the protective coating within the required installation window
• Applying insufficient protective coating thickness
• Using incompatible or unsuitable surface coatings
• Improper surface preparation
• Poor drainage or unresolved ponding-water conditions
• Failure to inspect and maintain the protective coating over time

Once the spray polyurethane foam has been applied, its protective coating or surfacing should be installed according to the current requirements of the specific roofing system. Required application timing, coating thickness, primers, and number of coats vary by manufacturer and product.

Physical damage should also be repaired before prolonged exposure affects the foam beneath.

Many SPF roofing problems can be reduced through proper roof evaluation, substrate preparation, trained application, appropriate weather conditions, correct coating thickness, and ongoing inspection and maintenance.

Concluding Thoughts on Spray Foam Roof Systems

For building owners and facility managers, spray polyurethane foam can provide useful roofing and insulation benefits when the building and existing roof are suitable candidates for the system.

SPF is not appropriate for every roof. Before installation or restoration, the roof should be evaluated for wet insulation, structural deterioration, drainage problems, damaged materials, failed seams or penetrations, and other conditions that may need to be corrected first.

A commercial roofing contractor can evaluate the building and discuss whether SPF roofing, another restoration system, repair, recover, or replacement is appropriate.

Written by: Ian Myers

Ian was the very first team member brought on by the founder of the Choice Roof Contractor Group to assist with nationwide growth. Since then he has written 120+ blog posts and provided excellent support to the roofing contractors in the group. Through his multiple roles in the commercial roofing industry, he has gained tremendous knowledge in the sector.