1. General Product Information

1.1 Product Type
1.2 Roofing Components
1.3 Roofing Categories
1.4 Industry-Specific Standards, Code Requirements, and Compliance
1.5 Unique Industry-Specific Flashing and Metal

Spray polyurethane foam (SPF) roofing systems are unlike factory-manufactured membrane roofs. SPF roofs consist of a thick layer of rigid, closed-cell, field-applied spray polyurethane foam that is seamless and fully adhered to its substrate. The SPF itself forms a waterproofing membrane and serves as insulation. SPF surfaces will degrade over time when exposed to the ultraviolet (UV) radiation of sunlight; therefore, SPF roofs are covered with a UV-protective coating or a layer of aggregate. Coatings also provide an additional degree of water resistance.

The Spray Polyurethane Foam Alliance (SPFA) Technical Documents referenced in this chapter are available at no charge. Registration and login are required.

1.1 Product Type

SPF roofing systems are closed-cell rigid polyurethane foams typically having a density of between 2.5 and 4.0 lb/ft3. The SPF is produced on-site by combining liquid components.

1.1.1 Identification and Traceability

SPF components are typically labeled as “A” component (polymeric diisocyanate or p-MDI) and “B” component (a proprietary blend). Materials are typically delivered to the job site in 55-gallon drums; each drum is identified with the manufacturer, contents, weight, surface burning characteristics, and instructions for storage, handling and installation.
Once applied, the SPF is typically indistinguishable from other SPFs; project records must be relied on to trace specific products.

1.1.2 Packaging and Storage

SPF liquid components are temperature sensitive and should be stored, shipped and handled in accordance with the manufacturer’s instructions.

1.2 Roofing Components

SPF roof systems are comprised of three main parts: substrate, SPF and coating/covering.

1.2.1 Substrates

SPF roof systems may be applied as new roofs, reroofs or recovers. As a new roof or reroof (with tear-off), typical substrates include decks, insulation boards or cover boards. As a recover, substrates may consist of an existing roof system (such as built-up and modified bitumen roofs), or existing roof systems may be covered with a mechanically attached insulation board or cover board. When insulation or cover boards are installed over a deck or an existing roof system, the method of attachment of the cover board (mechanical or adhesive) depends on the project specifics.

1.2.2 SPF

SPF provides the insulation and waterproofing membrane. SPF is spray-applied directly to a roofing substrate or prepared existing roof membrane. The SPF component chemicals are supplied to an SPF roofing contractor as a two-component system, typically identified as “A” component (polymeric diisocyanate or p-MDI) and “B” component (proprietary blend of polyols, flame retardants, blowing agents, catalysts and surfactants). The components are mixed in a spray gun under heat and high pressure; the liquid components react in place, on the roof substrate, and form a rigid, closed-cell foam mass within seconds of application, expanding 20 to 30 times its original volume.

Roofing spray foams are closed-cell, thermosetting, and have densities of approximately 2.5 to 4.0 lb/ft3 and R-values of approximately 5.5 to 6.5 per inch of thickness. Compressive strength of the SPF typically exceeds 40 psi.
Thickness of the SPF should be 1 inch at minimum and is typically greater to satisfy the R-value requirements of the project and to enhance drainage patterns.

1.2.3 Coatings and Coverings

SPF is sensitive to UV light damage. When exposed, the SPF surface will initially discolor (darken); eventually, the top surface skin will become friable. With time, the thickness of the SPF will erode. Protection of the SPF with a coating and/or other covering material is necessary for longevity of the roofing system.

1.2.3.1 Coatings

Common coatings used over SPF include acrylic, butyl, silicone, polyurethane, and polyurea. Coating systems are proprietary formulations with a variety of physical properties, fire ratings, impact resistance, and application methods. All coatings used over SPF roofs are elastomeric, meaning when fully cured, the coating is capable of being stretched to at least twice its original length (100 percent elongation) and will return to its original dimensions. See SPFA Technical Documents, “SPFA-102 A Guide for Selection of Elastomeric Protective Coatings Over Sprayed Polyurethane Foam”.

1.2.3.1.1 Acrylic

Acrylic coatings are single-component coatings based on acrylic polymers. They are water based, which allows for easy cleanup. Acrylic coatings have good resistance to weathering and a high moisture vapor transmission rate or permeability. There are quick-setting versions, which tend to form a skin faster than standard versions of acrylic coatings. There are also high-tensile versions, which tend to perform better under physical duress. Reference ASTM D6083 (Standard Specification for Liquid Applied Acrylic Coating Used in Roofing).

1.2.3.1.2 Butyl

Butyl coatings are elastomers with extremely low water-vapor permeability, which makes them especially desirable in situations that have relatively high vapor drive, such as low temperature applications (coolers, freezers, and cryogenic storage). When exposed to exterior weathering or used in applications where mechanical damage may occur, butyl coating should be top-coated with tougher or more weather-resistant coatings. (Consult with the coating manufacturer for specific recommendations.) While most butyl coatings are two-component materials, some single-component versions are available.

1.2.3.1.3 Silicone

Silicone coatings are silicone polymer elastomeric coatings. They are available as single-component materials. Silicone coatings are characterized by exceptional weather resistance and an ability to withstand temperature extremes, retaining physical properties. Silicone coatings have high vapor permeability. Silicone coatings are available in standard and high-solids versions. Reference ASTM 6694 (Standard Specification for Liquid-Applied Silicone Coating Used in Spray Polyurethane Foam Roofing Systems).

1.2.3.1.4 Polyurethane Elastomers

Polyurethane is a polymer reacted from an isocyanate and a polyol blend. There are numerous types of polyurethane coatings, which may be categorized by any of the following descriptors:

• Aliphatic
• Aromatic
• Modified
• Single-component
• Plural-component
• Moisture-cured

Physical properties, application methods, and cure times vary widely. See SPFA Technical Documents, SPFA-102 A Guide for Selection of Elastomeric Protective Coatings Over Sprayed Polyurethane Foam and the manufacturer literature for additional information.

1.2.3.1.5 Polyurea

Polyurea coatings are characterized as plural-component, fast-curing elastomeric coatings. Polyurea coating chemistry varies widely between formulations; some are classified as hybrid polyureas and/or hybrid polyurethanes. Most polyurea coatings are aromatic, but some aliphatic versions are available. Polyurea coatings provide a very tough coating that can be applied in a wide range of weather conditions, following the manufacturer dew point and surface moisture condition recommendations.

1.2.3.2 Other Coverings

In addition to using elastomeric coatings, SPF roofing systems may also be protected from UV exposure using various aggregates. Aggregate may be used as a supplement to a coating or by itself. See SPFA Technical Documents, SPFA-110 Spray Polyurethane Foam Aggregate Systems for New and Remedial Roofing.

1.2.3.2.1 Gravel/Slag

The selection of gravel or slag as a covering for a SPF roof is usually determined by local availability, with the size of the gravel/slag being more important than the type. A mixture of different gravel/slag sizes should be used, with larger pieces approaching 20 mm (3/4 in.). Flat-surfaced gravel/slag is preferable to round. Loose-laid aggregate should not be installed on roof areas with slopes greater than ½ in./ft.

1.2.3.2.2 Granules/Chips

Roofing granules and/or chips are often added to SPF roofs to provide traction, enhance durability, and increase fire resistance. They are available in a variety of grades and sizes. Typically, granules and chips are embedded into wet elastomeric coating to hold them in place.

1.3 Roofing Categories

1.3.1 Low Slope

Low-slope roofs are suitable platforms for SPF roofing systems. Ponding water-an accumulation of water in low-lying areas that exceeds the manufacturer specification and/or contract documents-should be avoided. Random, inconsequential amounts of residual water on a roof membrane are acceptable. Loose-laid, aggregate-covered SPF roofs are typically limited to roof slopes that are equal to or less than ½ in./ft, while coated SPF roofs may be installed on roofs of any slope.

1.3.2 Steep Slope

Coated SPF roofs may be installed on roofs of any slope.

1.4 Industry-Specific Standards, Code Requirements, and Compliance

Building code recognitions of SPF roofing systems are in 2015 IBC Section 1507.14 and 2015 IRC Section R905.14.

1.4.1 Hail

Impact resistance of SPF roofing products and assemblies are generally evaluated using FM 4470. Systems are rated for MH (moderate hail) or SH (severe hail); systems may also be unrated.

Under the IBC, impact resistance of SPF roofing systems is generally determined in accordance with the “Resistance to Foot Traffic Test” in Section 5.5 of FM 4470.

1.4.2 Wind

SPF roofing systems can be designed for use in any wind speed zone. SPF is an adhesive material that does not include fasteners in its attachment method.
In recover applications, the existing roof cover serves as the substrate and the uplift resistance of the SPF is dependent upon the existing cover’s securement to the deck, as well as the deck securement to the roof frame. Fasteners may affect wind uplift resistance and wind performance in cases where the SPF has been applied to a mechanically fastened substrate.

Wind uplift resistance of SPF roofing systems is generally determined by test standards such as FM 4474 or UL 580. Typically, the adhesion of SPF to the substrate to which it has been applied exceeds the testing capabilities of most test equipment. The mode of failure for tested assemblies tends to be the means of attachment of the substrate to the roof deck. In other words, the wind uplift resistance of an SPF roofing system is dependent on the substrate. Where an SPF roofing substrate is mechanically attached to the roof deck, the mode of test failure is usually the mechanical fasteners, the substrate, or the deck itself.

An exception to this occurs when SPF is applied directly to a roof deck. In this case, FM 4474 permits the use of a pull-test procedure (FM 4474, Appendix B). SPF roofing systems applied, for example, directly to a structural concrete roof deck may be tested in accordance with this procedure. Test results are usually very high, with tensile adhesive failures occurring at approximately 900 psf.
Many SPF roofing systems have been evaluated for code compliance by the ICC-Evaluation Service, Florida Product Approvals, Miami-Dade NOAs (Notices of Acceptance) and other evaluation agencies.

1.4.3 Fire

SPF roofing systems are generally tested for exterior and interior fire exposure. Exterior fire exposure tests include ASTM E108 and UL 790. Exterior fire exposure test results include the maximum roof slope, material thicknesses (SPF, coatings, granules, etc.), and combustibility of the roof deck (usually rated as NC – non-combustible, or as plywood thickness for combustible decks). ASTM E108 and UL 790 rates the assemblies as Class A, B or C, with A being the best.

Additionally, both the International Building Code (IBC) and the International Residential Code (IRC) require that the SPF (without coating or covering) used in roofing systems be tested for spread of flame in accordance with ASTM E84, with a maximum flame spread index of 75.

1.5 Unique Industry-Specific Flashing and Metal

SPF is self-flashing: that is, the SPF itself forms the flashing system for transitions between horizontal and vertical surfaces. There are usually no separate counter-flashings used. When required, flashing made from metal or other material should conform to the building code and good roofing practice.

2. Installation Guidelines

2.1 General
2.2 Substrate Preparation
2.3 SPF Application
2.4 Drainage Enhancement

2.1 General

SPF roofs are installed in a three-step process:

1. Surface preparation (Section 2.2)
2. SPF application (Section 2.3)
3. Covering application (Section 2.4)

2.1.1 Roof Weight Loads

Coated SPF roofs generally add less than 0.5 lb per inch of thickness. When recovering over an existing aggregate-covered roof, the weight of aggregate removed typically exceeds the weight of the new SPF roof. Aggregate-covered SPF roofs will add approximately 10 lb/ft² in dead load to the roof. When reroofing with SPF, evaluate the structural loading to assure code compliance and occupant safety.

2.1.2 Training and Qualifications of Applicator

SPF roofing systems must be installed by persons and contractors fully experienced and qualified in the installation of those roofing systems. SPFA offers a Professional Certification Program (PCP) to certify individual trade personnel, and accredit SPF contractors, distributors and suppliers.

2.1.3 Specialized Equipment

2.1.3.1 Proportioner and Associated Equipment

Because SPF is installed from a two-component system, the components must be pumped through a proportioning pumping system and through heated hoses to a spray-mixing gun. Proper setup and operation of the proportioner is crucial for successful SPF application. See SPFA Technical Documents, SPFA-137 Spray Polyurethane Equipment Guidelines.

2.1.3.2 Coatings

Coating applications require specialized equipment such as sprayers and mixers. See SPFA Technical Documents, SFPA-144 Coating Equipment Guideline.

2.1.3.3 Aggregate

Aggregate, when used, requires application equipment to transport it to and spread onto the roof surface. Equipment choice depends largely on project logistics. Equipment is typical of any used in the roofing industry and is not specific to SPF. Aggregate may be applied using pneumatic or mechanical spreaders; granules may be dispersed into wet coating using pneumatic grit-blasting equipment.

2.1.4 Weather/Environmental Considerations

SPF components are highly sensitive to water and moisture. SPF cannot be applied to wet or damp surfaces. Additionally, SPF systems are usually limited in the temperature ranges in which they may be applied. SPF manufacturers specify temperature and humidity limits for their specific products; these ranges vary from product-to-product as manufacturers often provide SPF systems designed for a variety of ambient and substrate temperatures. Windy conditions may lead to irregular SPF surface texture and/or overspray; special application techniques may be required. Coating system application may also be affected by weather conditions; specific manufacturers should be consulted.

2.1.5 Overspray

SPF is mixed and sprayed using an application gun that atomizes the mixed SPF components. The resulting small droplets may become airborne and deposited on unintended surfaces. Masking and other preventative techniques should be employed to avoid spray on unintended surfaces such as windows, doors, walls, cars, etc. The sprayed coating systems may also result in overspray.

2.1.6 Details

SPF roof details may be found in SPFA Technical Documents, SPFA-104 Spray Polyurethane Foam Systems for New and Remedial Roofing and SPFA-110 Spray Polyurethane Foam Aggregate Systems for New and Remedial Roofing.

2.2 Substrate Preparation

SPF can be successfully applied to most construction surfaces. Whether an SPF roof is being applied as a recover to an existing roof or being applied directly to a roof deck, the surface of the substrate needs to be prepared to receive the SPF. Surface preparation addresses substrate security (e.g., for wind uplift resistance); substrate cleanliness and dryness (for adhesion); substrate configuration (e.g., corrugated metal decks require treatment to provide a flat surface for SPF application); etc. Substrates to which SPF is to be applied must be structurally secure; dry; free of loose gravel, dirt and other debris; and free of contaminants (such as oil and grease) which would affect SPF adhesion. Priming may be required based on manufacturer’s specifications. Additional information is available in SPFA Technical Documents, SPFA-138 Guideline for Roof Assembly Evaluation for Spray Polyurethane Foam (SPF) Roof System.

2.3 SPF Application

SPF must be applied by fully qualified applicators, using high-pressure proportioning two-component spray equipment. Specific application instructions are available from the SPF manufacturer. In general, application guidelines include:

• Inspection of the substrate
• Review of weather conditions (including ambient temperature and humidity)
• Review of manufacturer instructions and project specifications
• Minimum SPF pass thickness of ½ in.
• Maximum SPF pass thickness per manufacturer instructions (typically 1 ½-2 in.)
• Apply total thickness required for specified drainage and insulation (R-value)
• Follow good workmanship and roofing practices when terminating SPF or transitioning SPF from horizontal to vertical surfaces
• Apply the full specified thickness of SPF to any given roof area the same day
• Assure the surface texture of the SPF is suitable for application of the protective coating/covering

Additional information can be found in the following SPFA Technical Documents, SPFA-104 Spray Polyurethane Foam Systems for New and Remedial Roofing and SPFA-110 Spray Polyurethane Foam Aggregate Systems for New and Remedial Roofing.

Coating application generally proceeds in two steps: base coat and top coat. Total coating thickness is usually measured as dry film thickness (DFT) in mils (1/1000 of an inch). Minimum total coating DFT is manufacturer-, product-, and project-specific, but is generally between 20 and 40 mils. Specifics may be found in SPFA Technical Documents, SPFA-104 Spray Polyurethane Foam Systems for New and Remedial Roofing. In general, the following apply:

• Base coat is applied the same day or within 24 hours after the SPF.
• SPF surfaces shall be free of dust, dirt, contaminants and moisture before base coat application.
• Base coat shall be applied in uniform thickness with the application rate being governed by the SPF surface texture. Minimum DFT shall meet the manufacturer and project specification requirements.
• Base coat shall be inspected and repaired as needed, prior to subsequent coats. Base coat shall not be applied during periods of inclement weather.
• Base coat and top coat are normally of contrasting color to aid in judging application thickness.
• Top coat should be applied in a timely manner to ensure proper adhesion between coats.
• Top coat shall be applied in uniform thickness with the application rate being governed by the SPF surface texture. Minimum DFT shall meet the manufacturer and project specification requirements.
• The cured DFT of the finished multiple coat application shall be checked by taking slit samples and examining them under magnification. Areas found to have less than the minimum total thickness will require additional coating.

2.3.1 Aggregate/Granules

Application of aggregate and granules follows generally accepted roofing practices. Granules may be embedded into a final pass of wet coating. Aggregate will be loose-laid on flat areas with sloped and vertical surfaces coated. Overall aggregate thickness should be a minimum of ¾ inch or sufficiently thick to provide UV protection. Additional information on aggregate-covered SPF roof systems can be found in SPFA Technical Documents, SPFA-110 Spray Polyurethane Foam Aggregate Systems for New and Remedial Roofing. Information on granule application can be found in SPFA Technical Documents, SPFA-104 Spray Polyurethane Foam Systems for New and Remedial Roofing.

2.4 Drainage Enhancement

Unlike other roofing membranes, SPF can be easily applied in varying thicknesses. This allows for the enhancement of drainage by applying a greater thickness of SPF in low-lying areas. Typically, the low areas are sprayed first to create an overall drainage plane, followed by additional SPF passes to achieve specified thicknesses. Additionally, drainage may be enhanced prior to SPF application by adding drains, and after SPF application by sculpting the SPF surface (while maintaining specified thicknesses).

2.5 Photovoltaic (PV) Equipment

Planning is recommended before the integration of a PV system with a SPF roof to ensure optimum performance of the SPF roof. Specific recommendations include:

• Primary access routes to and through the PV array should be determined, and walkways should be provided
• All vertical mounts or stanchions and framing members should be installed prior to SPF application
• PV panels should be elevated sufficiently to provide access for future roof maintenance
• Stanchions should be directly anchored to the structural deck or structural members to avoid the use of horizontal support members fastened to the deck, which may restrict water flow
• Temporary protection of the SPF roof system should be provided during installation of the PV panels

3. Repair and Maintenance Guidelines

3.1 Natural Aging vs. Damage
3.2 Inspection and Maintenance
3.3 Expected Product Lifecycle

SPF roofs are sprayed in place, fully adhered and seamless, and tend to be leak resistant. The SPF forms a membrane of at least 1-in. thick, which helps to prevent water entry into the building or water transmission within the roof system as a result of surface damage due to hail or wind-borne debris. Repair of SPF roofs with minor surface damage becomes a minor maintenance procedure and can usually be accomplished with a caulk.

For more specific information regarding the inspection, assessment and minor repair of SPF roofs, see the following SPFA Technical Documents:

• SPFA-127 Maintenance Manual for Spray Polyurethane Foam Roof Systems
• SPFA-139 Recommendations for Repair of Spray Polyurethane Foam Roof Systems due to Hail and Wind Driven Damage
• SPFA-107 Spray Polyurethane Foam Blisters

3.1 Natural Aging vs. Damage

Natural aging of a SPF roof occurs as the protective coating becomes thinner, possibly exposing the foam to UV degradation. Thinning areas can be recoated and refurbished at the end of the coating service life. Damage includes divots, gouges, splits, and holes due to flying debris, mistreatment, fire, excessive mechanical wear or excessive UV exposure.

3.2 Inspection and Maintenance

SPF roof systems should be regularly inspected. Two inspections, one in the spring and one in the fall, are recommended annually. The roof should be inspected for coating wear; exposed, wet, or cracked foam; separation of foam from flashings; blisters; pinholes; mechanical or bird damage; and other damage or defects. Drains and gutters should be cleaned if clogged with debris. Areas around units or any new installations should be checked for damage. Small punctures or deviations can usually be repaired with a compatible sealant or other similar materials. For more severe problems, destructive investigation such as cutting slits in the SPF or core sampling may be necessary. For more details and general guidance, see SPFA Technical Documents, SPFA-127 Maintenance Manual for Spray Polyurethane Foam Roof Systems.

3.3 Expected Product Lifecycle

SPF roofs are considered sustainable and renewable. Historical data indicate that maintained SPF roofs exhibit life spans in excess of 30 years. The primary technique to assuring the long life of an SPF roof is to inspect it regularly and maintain its protective coating/covering. Coating systems generally need to be re-applied every 10 to 20 years (depending on the generic type of coating, the original thickness and other factors). Aggregate covering systems require inspections seasonally and following wind events; areas of SPF exposure, such as wind scour, need to be repaired. See SPFA Technical Documents, SPFA-122 The Renewal of Spray Polyurethane Foam and Coating Roof Systems for further information.

4. Damage Issues

4.1 General Information
4.2 Determining Hail Damage
4.3 Determining Wind Damage
4.4 Determining Fire Damage
4.5 Determining Cold Weather Damage

4.1 General Information

Damage caused to SPF roofs due to wind-driven debris and objects including hail, typically do not cause the roof system to leak. Damage can usually be repaired economically and does not require roof replacement. Wind events rarely, if ever, will separate the SPF from the substrate to which it has been applied. However, wind events may cause the SPF’s substrate to separate from its underlying structure (an example would be when SPF had been applied to an existing BUR as a recover and the wind event caused the BUR to detach from the roof deck); in such cases temporary repairs would be required to prevent water infiltration into the building.

SPF has been used successfully to temporarily patch or dry in a variety of roof systems where wind and wind-borne debris has damaged its integrity.

4.2 Determining Hail Damage

Hail by its very nature can cause a variety of damage to an SPF roof. The degree of damage is dependent on hail size and density and the coating/covering characteristics. Table 1 in SPFA Technical Documents, SPFA-139 Recommendations for Repair of Spray Polyurethane Foam Roof Systems due to Hail and Wind Driven Damage provides damage assessment levels and recommended repair techniques.

4.3 Determining Wind Damage

4.3.1 Windborne Debris

Windborne debris may cause damage-such as gouges and slits or divots in the foam-to the SPF roofing system. After a severe weather event, the roof should be inspected as soon as possible and necessary repairs completed. See SPFA Technical Documents, SPFA-139 Recommendations for Repair of Spray Polyurethane Foam Roof Systems due to Hail and Wind Driven Damage for damage assessment and repair recommendations.

4.3.2 Wind Uplift

Wind events may damage an SPF roof system, causing substrate or deck uplift and failure. Damage will be obvious in nature, and the repair techniques are dependent upon the degree of damage. If the deck is intact, temporary and permanent repairs may be made with SPF.

4.3.3 Aggregate Scour

High wind may cause aggregate covering to scour, particularly in roof corners and around roof-mounted equipment where wind vortex and funneling effects may occur. Repair techniques include redistribution or replacement of the aggregate. Aggregate in wind-scour prone areas may be embedded into wet coating for stabilization.

4.4 Determining Fire Damage

Fire damage is unique, and repair recommendations are highly dependent upon the extent of the damage. Signs of fire damage include charred or blistered foam and significant discoloration in proximity of the fire. Damage areas could be small to large in size, with the deck and structure damaged as well. Consult with a qualified contractor and system manufacturer to determine the best course of action.

4.5 Determining Cold Weather Damage

SPF systems are typically not subject to damage caused by cold weather.

5. Industry Resources

5.1 Industry Associations
5.2 Technical Bulletins/Installation Guides
5.3 Technical Support Contacts
5.4 Member Lists

5.1 Industry Associations

The Spray Polyurethane Foam Alliance (SPFA) is the industry’s trade association. Founded in 1987, SPFA is the voice, and educational and technical resource, for the spray polyurethane foam industry. A 501(c)(6) trade association, the alliance is composed of contractors, manufacturers, and distributors of polyurethane foam, related equipment, and protective coatings. SPFA members also provide inspections, surface preparations, and other services. The SPFA supports the best practices and the growth of the industry through a number of core initiatives, which include educational programs and events, the SPFA Professional Installer Certification Program, technical literature and guidelines, legislative advocacy, research, and networking opportunities.

Visit SPFA for more information.

5.2 Technical Bulletins/Installation Guides

SPFA maintains an extensive library of roofing guides in SPFA Technical Documents and SPFA Tech Tips.

5.3 Technical Support Contacts

Spray Polyurethane Foam Alliance (SPFA)
3927 Old Lee Highway, #101B
Fairfax, VA 22030
800-523-6154
Email: Link in the Contact Us section of the website: www.sprayfoam.org/contact-us

5.4 Member Lists

SPFA member manufacturers and contractors may be found on the SPF website: www.sprayfoam.org