Types of Single-Ply Roofing Systems

All roofs feature some slope to allow for drainage. Low-slope—sometimes referred to as “flat”—roofs generally feature a very slight slope of less than 3:12. Slopes are represented as a ratio of how much the roof rises (vertical) over the distance (horizontal) between its lowest edge and its highest edge. A 3:12 slope indicates a rise of 3 inches over a 12-inch distance.

Different Types of Low-Slope Roofing Systems

• Built-up Roof (BUR) Membrane Systems. Built in several layers, including insulation board, perlite, inter-ply sheets, asphalt, and pea gravel ballast repeated in various combinations.
• Polymer-Modified Bitumen Sheet Membrane Systems. Built with reinforced bitumen membrane fabrics that are either mopped on using hot asphalt, heat welded, or torch applied.
• Spray Polyurethane Foam-Based (SPF) Systems. Built by spraying foam consisting of heated and properly proportioned isocyanate and polyol.
• Single-Ply Membrane Systems. Built by applying a single layer over a roof structure or insulation board.

This article provides an in-depth discussion of the three types of single-ply roofing systems, highlighting their characteristics, applications, and advantages and disadvantages.

Types of Single-Ply Roofing Systems

Single-ply roofing systems utilize flexible sheets of thermoset or thermoplastic membranes. Both types of membranes have unique attributes. For example, thermoplastics can be melted and reused multiple times, while thermosets remain solid after curing. The three main types of compounds used in single-ply membrane systems are:

• Ethylene propylene diene terpolymer (EPDM): a thermoset
• Polyvinyl chloride or polymerized vinyl chloride (PVC): a thermoplastic
• Thermoplastic polyolefin (TPO): a thermoplastic

EPDM Roofing

EPDM is a synthetic rubber composed of ethylene and propylene. EPDM roofing membranes are available as large rolls in black or white, with widths ranging between 7.5-50 feet and thicknesses of 45, 60, or 90 mils. These roofs typically last between 10 and 25 years.

Common installation methods for EPDM roofing include full adhesion, mechanical attachment, or ballasting followed by gluing or taping of the seams. EPDM roofs are suitable for large commercial buildings like warehouses, office buildings, hotels, shopping centers, schools, and universities.

Advantages of EPDM roofing systems include:

• Resistance to hail and abrasion
• Durability in extreme weather conditions
• Flexibility in cold weather climates
• UV radiation resistance
• Easier installation, especially at flashings and penetrations
• Cost-effectiveness

Disadvantages of EPDM roofing systems include:

• Higher risk of structural overheating in extreme heat due to heat absorption
• Prone to punctures, limiting foot traffic on the roof
• Shrinkage in dry, hot climates

PVC Roofing

PVC is a synthetic, thermoplastic polymer that offers resistance to wind, moisture, fire, and chemicals. PVC roofing material comes in rolls of 50-100 feet long and 5-12 feet wide. It can be installed using full adhesion, mechanical fastening, or ballasting and seam welding methods.

A PVC roof system has a lifespan ranging from 15 to 30 years. The smaller rolls of PVC roofing material make it easier to handle and install, making it suitable for smaller commercial and residential projects.

Advantages of PVC roofing systems include:

• High strength (up to 350 pounds per square inch breaking strength)
• Durability due to welded seams
• Superior resistance to moisture, wind, fire, and chemicals
• Versatility for additional applications like patios, decks, and balconies
• Reflective surface

Disadvantages of PVC roofing systems include:

• Higher material costs
• Potential loss of reflectivity over time due to air pollution
• More laborious installation due to less flexible membrane, especially at flashings and penetrations

TPO Membrane Roofing

TPO membrane roofing systems are gaining popularity in the commercial roofing market. These systems feature a single layer of synthetic thermoplastic combined with reinforcing scrim that provides a naturally reflective surface, UV radiation resistance, and durability. TPO roofing material comes in rolls with widths of 10, 12, or 20 feet and is installed using mechanical or adhesive attachment with heat-welded seams.

The lifespan of a TPO membrane roofing system ranges from 7 to 20 years. TPO roofs are suitable for various applications that overlap with EPDM roofing systems.

Advantages of TPO roofing systems include:

• Reflective surface for UV radiation protection
• High strength compared to EPDM
• Durability due to heat-welded seams
• Excellent wind resistance
• Cost-effectiveness

Disadvantages of TPO roofing systems include:

• Less flexibility, making installation more laborious, especially at flashings and penetrations
• Shorter lifespan compared to other roofing systems

Contact Knickerbocker for Your Roofing Needs

At Knickerbocker Roofing and Paving Co., Inc., we offer a wide range of low-slope roofing systems for commercial, industrial, and historical buildings, including EPDM, PVC, and TPO roofing systems. Our expert team performs all roofing, sheet metal, and carpentry work in-house. We maintain certifications from major roofing system manufacturers and conduct project safety inspections. We also offer roof inspections and evaluations at no cost and provide annual roofing application and safety training programs.

For more information about our single-ply roofing solutions or to partner with us on your next project, contact us or request a quote today.