Not that long ago, maintenance and engineering managers tended to stick with the roofing systems with which they were most familiar. They were system loyal, so roofing retrofits usually replaced one type of system with the same type. More often today, however, managers investigate the benefits and drawbacks of a range of systems, largely in the recognition that manufacturers have incorporated new materials and formulations into their products to meet customer expectations.
One example of this trend in continuous product improvement is in ethylene propylene diene terpolymer (EPDM) roofing systems. EPDM systems often are referred to as rubber roofs or membrane roofs, and they have become the most commonly used roofing systems for both re-roofing and new construction projects in the United States.
All parties involved in the specification, installation, and ongoing maintenance and inspection of roofing systems — including in-house maintenance directors, building owners, and design professionals — have shown greater interest in EPDM systems in recent years.
The EPDM rubber roofing membrane is an elastomeric polymer synthesized with: clay for fire resistance and dimensional stability; carbon black to increase tear strength and resistance to ultraviolet light; process oils for flexibility; and curing agents for vulcanization.
Membranes are manufactured as two plies, and they are laminated together to form a single ply in sheet sizes up to 50 feet by 200 feet. Next, the membrane is cured under heat, steam and pressure in an autoclave.
Membranes are produced in thicknesses of 45, 60, 75 and 90 mils. EPDM systems in recent years have been manufactured with an option of reinforcements with high-tenacity polyester treated for wick resistance.
Among the most attractive features of an EPDM roofing system is its ability to retain its physical characteristics throughout its service life. EPDM compounds have demonstrated a high degree of stability under exposure to ultraviolet light, as well as in extremely high and low temperatures. These benefits allow managers to specify and install EPDM membranes in any geographic area of the country, regardless of weather conditions. EPDM’s strength and overall system performance also help to protect the integrity of a building and the potentially millions of dollars of assets and operations that it contains.
The EPDM membrane also offers design flexibility, making it an attractive option for diverse applications. Among the earliest designs was the ballasted roof, in which the membrane is loosely laid over the substrate or insulation and covered with a layer of ballast — either stone or pavers — to keep the membrane in place when exposed to wind uplift.
Other common application options include fully adhering the membrane, which involves using a specified bonding agent to adhere the membrane typically to rigid insulation boards that are anchored to the deck.
These options eliminate the weight of the ballast and offer lightweight solutions for new or retrofit applications.
Arguably the most important benefit of an EPDM system is the membrane’s flexibility. This feature allows managers to specify it for a variety of roofing applications, from low-sloped roof decks to steep-sloped, barrel-roof systems. Because of its adhesive-style application and the ability of the material to maintain its physical characteristics, EPDM is ideal for complex roofing projects.
EPDM systems are worth considering when the roof has large empty expanses because they are available in 10- and 20-foot-wide rolls, minimizing seams. In these situations, repairs to membranes using electrical heat welders may be a problem without a very long extension cord.
Mechanically attached membranes generally are not the preferred way of installing single plies over structural concrete decks but are good for use on steel or wood. A fully adhered or ballasted system is more appropriate for structural concrete to avoid concrete damage.
Ballasted systems are not appropriate for engineered-steel structures unless the structure was designed for a ballasted roof. In every case, without exception, if a ballasted system is considered, an engineer should determine if the structural system will hold the weight. Do not use ballasted systems where high wind conditions might occur. Ballasted systems are appropriate when an inverted roof membrane assembly is considered or if first cost is the only criterion. Mechanical attachment and fully adhered systems are appropriate for both tear off and re-cover roofs.
Managers should evaluate single-ply membranes for chemical composition if they are being installed where hydrocarbon emissions are a problem. EPDM-based membranes are sensitive to hydrocarbons and should not be used.
One of the most attractive qualities of EPDM roofing is its relatively low installation cost, compared to alternative roofing systems. The installation of the roofing membrane is performed without any heat, dangerous fumes or heavy machinery. Aside from equipment used for adhesive application, no special equipment is required to lay down EPDM panels.
Because of the relatively basic installation process, the contractor labor costs involved in installing an EPDM systems tend to be significantly lower when compared to other systems. Combined with long-term warranties — some for as long as 30 years — and the ability to install the system easily over an existing roof system, an EPDM system often is an attractive option for either new roofing or re-roofing projects.
EPDM membrane formulations have remained relatively steady for the past 30 years; many of the roof systems that were installed in the 1970s still are performing well. Even so, EPDM manufacturers have continued to roll out product innovations.
And in response to technological advancements, membrane research and contractor requests for more ergonomic products, EPDM accessory products also continue to evolve to meet the demands of facilities.
The innovation of seam tapes in the 1980s to replace liquid adhesives has resulted in greater productivity for the contractor and enhanced performance for the roof system and in-house manager. Self-adhering components — components that have factory-applied adhesive tape — have increased roof system quality, especially in more problematic areas, such as flashing installations.
The 90-mil EPDM roof system is a highly puncture-resistant and tough membrane that offers the thickest layer of monolithic waterproof protection in the roofing industry. Also, 30-year warranties are now available. This is the only long-term performance guarantee in the roofing industry and can include warranty coverage for punctures, hail damage and wind speeds of up to 100 miles per hour.
Cleaning an EPDM membrane thoroughly is critical before applying a coating to the membrane surface. Many experts believe that an acrylic coating applied to the membrane can extend the roof system’s service life. These acrylic coatings are available in a variety of colors.
Another benefit of coating a roof is the possibility of increased reflectivity, which benefits facilities by lowering both the roof temperature and the building’s cooling load. If a coating is properly applied on a clean surface and to the specified application thickness, it can be a great benefit in prolonging the life of the roof system.
The many long-term benefits of the EPDM roofing system make it a viable roof application in various situations. In terms of installation cost, long-term warranties, life-cycle cost and overall system performance, EPDM is an attractive option that managers would be wise to consider.
EPDM Inspection InsightsWhen inspecting an existing EPDM roof system, roofing consultants, maintenance and engineering managers and other individuals responsible for a building’s maintenance and performance should look for these conditions:
Workers can repair many of these defects by cleaning the membrane thoroughly and using tape products recommended by the manufacturer. Workers using any adhesive product on an EPDM membrane should completely clean the area where the adhesion will occur. Dust and dirt reduce the ability of tape to adhere to the membrane, making it possible for the repair to peel up and allow water into the substrate or insulation. — Craig Dolgin |
Spotlight: ERA
The EPDM Roofing Association (ERA) was formed to address the need for current and accurate data documenting the benefits of EPDM roofing systems. EPDM single-ply rubber membrane roofing products have gained industry acceptance and respect by providing long-term, economically efficient, dependable roofing solutions for the construction community. |
Craig Dolgin is director of operations for Roof Resources Inc., a national roofing management company headquartered in Louisville, Ky.
