Back to Basics is an article series that highlights important but possibly overlooked information facilities management professionals should know.
Roof systems play an essential role in waterproofing a commercial building’s envelope. As part of the comprehensive roof system, single-ply roof membranes serve as the first line of defense against the elements, protecting critical equipment in warehouses, manufacturing facilities, hospitals, schools, data centers, and countless other facility types.
Roof membrane integrity—or the ability for the membrane to withstand common stressors—is key to assessing its performance and suitability for specific applications. That’s why building owners, facilities managers, and other key stakeholders should maintain an understanding of roof membrane materials and options. Comparing factors like material properties, costs, installation and maintenance considerations, and overall service life will help to identify the best membrane selection for a specific facility’s needs and ensure longevity.
In this article, we’ll walk through common single-ply membrane types, best practices for roof maintenance, typical causes of degradation, and how to know when it’s time to consider a roof replacement.
Examining Common Roof Membrane Types
Low-slope commercial roofs often include one of four types of single-ply membranes: thermoplastic polyolefin (TPO), polyvinyl chloride (PVC), ethylene propylene diene monomer (EPDM), or ketone ethylene ester (KEE). Each has a distinct chemical composition: EPDM is a synthetic rubber, TPO is a blend of polypropylene and rubber, PVC is a plasticized vinyl, and KEE is a PVC formulation enhanced with a solid polymer plasticizer for improved performance.
EPDM and TPO are commonly utilized membrane options, typically due to their low initial costs compared to PVC or KEE. TPO, in particular, has become one of most widely installed membranes in the U.S. due to its low purchase cost, common installation practices, white reflective surface, and broad familiarity among commercial roofing contractors.
Pricing is just one consideration stakeholders should weigh when selecting the optimal roof membrane for a given facility; equally valuable is how different membrane types impact performance. For example, KEE membranes are optimal for demanding environments or any application where high-performance and longevity are desired. KEE provides exceptional resistance to chemicals, severe weather events, wear and puncture, and other common forms of membrane damage. This makes KEE membranes an ideal choice for facilities like airports and chemical processing plants that regularly see harsh conditions; high-occupancy buildings like hospitals and schools, data centers, and military sites where downtime can be massively disruptive; and other high-stakes environments.
Independent laboratory testing confirms these claims. According to a report by Trinity | ERD, an architecture and engineering consultant specializing in building envelopes, a KEE-based membrane compliant with ASTM D6754 (more on this shortly) outperformed several proprietary PVC membranes in key areas, including:
- Breaking strength;
- Bursting strength;
- Tongue tear;
- Jet fuel resistance;
- Compressor oil resistance; and
- Hexane resistance.
Additionally, fire performance varies significantly among roof membranes. A KEE membrane was found to be self-extinguishing, which also helps prevent fire from spreading across the roof. In contrast, TPO is a highly combustible polymer that requires significant flame retardants that only slow the spread of flame. Cone calorimetry testing, a method used to evaluate how materials react to fire, has demonstrated that TPO burns at twice the heat of KEE. TPO exhibits a 40% higher rate of flame spread and a greater likelihood of igniting nearby materials compared to KEE.
When high performance is desired, it’s important that your roof membrane must meet the relevant testing specifications. For example, a KEE-based membrane should comply with ASTM D6754, which specifies KEE as the primary polymer and requires a robust fabric reinforcement to enhance durability. Since not all KEE-formulated membranes comply with this standard, building owners can have greater confidence in the reliability and resilience of membranes that do.
Maintenance Best Practices and Evaluating Roof Condition
Regardless of your roof membrane type, every commercial roof requires attention to ensure long-term performance and reliability. Regular maintenance is necessary to achieve full potential of the roof’s service life.
Roofs should be inspected at least twice a year, typically in the fall and spring. These inspections are intended to assess the overall condition and identify any issues that might require repair. Key issues to look for include:
- Punctures and cuts;
- Open seams or flashing separation;
- Stresses on seams and fasteners from foot traffic or thermal movement;
- Failed sealants around penetrations, edges, and seams;
- Degradation associated with exposure to chemicals, UV, and heat from the sun or ponding water;
- Debris buildup, including organic matter and foreign objects;
- Blocked drainage paths or other drainage issues; and
- Interior water stains or signs of leaks.
Any issues discovered should be addressed promptly. Unrepaired open seams or puncture damage can lead to severe and costly consequences. For building owners and managers, partnering with a qualified roofing professional for routine inspections, timely repairs, and documentation supports a comprehensive asset management strategy.
Evaluating Your Roof’s Condition
The frequency of repairs can be a strong indicator of your roof’s overall health. A useful tool for assessing overall roof condition is the Roof Condition Score (RCS)—a comprehensive, 100-point scale that evaluates all major components of the roof system.
RCS provides an objective, holistic snapshot of roof health and serves as a useful benchmark for comparing conditions across multiple facilities. The scoring categories are as follows:
- Good condition (RCS 71-100). Extensive life remaining. Continue with regular inspection and preventative maintenance.
- Fair condition (RCS 41-70). Midway through its life cycle. Continue maintenance and restoration as needed.
- Poor condition (RCS 0-41). Approaching failure. Maintenance and repairs may become ineffective and cost prohibitive.
Professional roofing contractors and consultants can assist with RCS evaluations and recommend appropriate next steps for inspection, maintenance, or replacement.
Making informed decisions when specifying a roof membrane and following maintenance best practices can be the difference between sustained operational security and negative consequences of roof failure, and downtime. By understanding the options available and prioritizing roof membrane integrity, facilities managers can enhance their buildings’ resistance to environmental stressors and protect critical infrastructure for the long haul.
Tanner Duer, FiberTite senior roof design consultant with Seaman Corp., brings 10+ years of extensive experience in the roofing industry, blending business development, project management, and hands-on expertise as a former roofing contractor. Duer’s in-depth knowledge of roofing systems, coupled with his technical acumen, allows him to deliver expert guidance to roof design professionals on commercial and industrial projects.