Spray Foam Roofing: Top 3 Problems

Spray foam roofing is the most energy-efficient roof system in the world. However, it's not the best solution for every roof, and you should know it's limitations before considering it for your roof. From weather constraints during installation to the risk of overspray and the challenge of finding a qualified contractor, in this article we'll talk all about potential spray foam roofing problems you should consider before choosing it for your building.

Table of Contents

• What is Spray Foam Roofing?
• Problem #1: Sensitivity to Weather Conditions
• Problem #2: Overspray
• Problem #3: Limited Pool of Qualified Contractors

What is Spray Foam Roofing?

Spray foam roofing, also called spray polyurethane foam (or SPF) is a roofing system that involves the application of a liquid polyurethane foam. It's often applied over an existing roof membrane, but can also be applied directly to the roof decking. The liquid foam is sprayed onto the roof surface, where it rapidly expands, creating a solid, continuous layer that adheres directly to the substrate. This roofing system is known for its excellent thermal insulation properties, as well as its ability to create a seamless, leak-resistant surface, without the seams and flashings that normally become leak points on a roof.

Key Components of Spray Foam

• Polyurethane Foam: The primary material in spray foam roofing, polyurethane foam is a cellular plastic material that combines two components—polyol and isocyanate—to produce a foam that expands and hardens upon application.

• Protective Coating: After the foam layer is applied, it is coated with a protective layer made of silicone, acrylic, or polyurethane elastomers. This coating is necessary to protect the foam from the sun's UV rays (which will otherwise damage it) and to create a waterproof barrier.

Advantages of Spray Foam

• Energy Efficiency: The thermal insulating properties of spray foam can significantly reduce heating and cooling costs (up to 30% annually in many cases).

• Leak Prevention: The seamless nature of spray foam roofing makes it highly effective at preventing leaks, as there are no joints or seams that can become potential weak points.

• Ease of Installation: In many cases, spray foam can be applied directly over an existing roof, eliminating the need for tear-off and disposal of old roofing material.

• Benefits for the Environment: Because spray foam is both energy-efficient and can be applied over an existing roof assembly, it can eliminate landfill waste and reduce carbon emissions. In many cases, spray foam reduces energy usage by 25-40% annually.

Applications for Spray Foam

Spray foam roofing is suited for flat or low-sloped roofs and can be applied over a variety of substrates, including metal, single-ply systems like TPO, and concrete. It is commonly used in commercial, industrial, and agricultural buildings.

Problem #1: Sensitivity to Moisture & Temperature

Similar to elastomeric roof coatings, spray foam insulation has specific temperature requirements for application. The foam shouldn't be applied if the temperature is below 55 degrees Fahrenheit. If it is, the foam won't form it's intended closed-cell structure, compromising its structural integrity and waterproofing capabilities.

Moisture is also a critical concern. The surface where the foam is to be applied must be completely dry. Even trace amounts of moisture can prevent effective bonding between the foam and the substrate. This is why It's essential for contractors to eliminate dew from the roof each morning and stop working before dew begins to fall in the evening.

Repercussions of Incorrect Installation

If installed under less-than-ideal conditions, spray foam roofs can suffer from a range of issues. These can include poor adhesion, leading to parts of the roof peeling off over time, or uneven foam expansion, resulting in weak areas that are less resilient to weather and may require costly repairs. In worst-case scenarios, moisture can get trapped in the foam, creating blisters.

Problem #2: Overspray

Another potential drawback that building owners and contractors must consider when opting for spray foam roofing is the issue of overspray. The nature of spray foam application—often carried out using specialized spray guns or hoses—makes it difficult to perfectly control the distribution of foam, particularly on windy days.

What is Overspray?

Overspray refers to the unintended dispersion of spray foam particles beyond the targeted application area. The foam particles can land on adjacent surfaces like walls, cars, or outdoor equipment, causing aesthetic and functional issues that can be time-consuming and expensive to fix. A little bit of overspray is not a terrible problem, because the foam particles will burn up in the sun. But a lot of overspray will stick stubbornly to most surfaces, and can cost hundreds of dollars to remove.

Factors That Contribute to Overspray

The risk of overspray is particularly elevated in certain conditions, such as high winds, close proximity to other buildings, or complex roof geometries that make precise application challenging.

Mitigating Overspray Risks

Preventative measures can be taken to mitigate the risk of overspray, such as the use of wind screens, or scheduling the spray on days with minimal wind. However, these precautions add another layer of complexity to the planning and installation process. 

Problem #3: Limited Pool of Qualified Contractors

When it comes to the installation of spray foam roofing, one drawback that doesn't often get as much attention as it should is the difficulty of finding a qualified contractor. Unlike traditional roofing materials that are familiar to most contractors, spray foam roofing requires a specialized skill set that not all roofing professionals possess.

The installation of spray foam roofing involves a complex process that includes surface preparation, precise application, and the proper handling of specialized equipment. This requires a contractor who is specifically trained and certified in foam application, understands the material properties, and can manage the challenges that may arise during the installation, such as avoiding overspray.

Because of the specialized skills needed, the pool of qualified contractors is significantly smaller compared to those familiar with more traditional roofing materials like asphalt shingles or  single-ply. 

The Risks of Inexperienced Contractors

Opting for a contractor who is not specialized in spray foam roofing can lead to a host of problems, from poor installation quality that compromises the roof's integrity and durability, to failure in meeting building codes and regulations. Even small errors in foam application can lead to significant issues like leaks, poor insulation, and decreased lifespan of the roof, requiring costly repairs or even complete re-installation.

The Upshot

Spray foam roofing offers a range of benefits, from high thermal resistance to leak prevention. However, the drawbacks can't be overlooked. Whether it's the specific conditions required for an optimal installation, the potential for overspray affecting adjacent areas, or the challenge in finding a certified and skilled contractor, each issue poses risks that could lead to additional costs and complications. Being informed and planning accordingly can help mitigate these risks, but it's crucial to weigh the pros and cons carefully before committing to this type of roofing system.

If you have specific questions about using spray foam roofing on your building, give us a call. In a free, 30 minute discussion, our experts can provide you with customized advice.