Consortium to Evaluate Performance of Tape-Bonded Seams for Sealing EPDM Roofing Membranes

Five companies and two trade associations have joined the National Institute of Standards and Technology in a cooperative research consortium to evaluate the performance of pre-formed tape for bonding seams in EPDM membranes, a system commonly used to make low-sloped roofs watertight.

The EPDM Seam Consortium was established to provide neutral- party, peer-reviewed performance data on tape-bonded seams needed by roofing contractors, consultants and manufacturers. Data gathered by the consortium will be used to develop a test protocol and recommended criteria for evaluating the performance of pre-formed tape systems in EPDM membranes.

Members of the consortium are ADCO Products Inc., Ashland Chemical Co., Carlisle SynTec Systems, Firestone Building Products Co., Genflex Roofing Systems, the National Roofing Contractors Association and the Roof Consultants Institute. A supporting sponsor of the consortium's work is the U.S. Army Construction Engineering Research Laboratories.

EPDM, a synthetic rubber (a terpolymer of ethylene, propylene and a diene) material, is placed in overlapping sheets to form a membrane atop a roof. EPDM roofing systems were introduced in the mid-1970s and, today, account for about 30 percent of the low-sloped roofing systems installed annually.

Overlapping sheets of EPDM installed on a roof must be bonded together to ensure a watertight surface. Solvent (liquid)-based adhesives formulated with volatile organic compounds have been the most commonly used bonding agents, although solvent-free, pre-formed tapes have been available for a decade. The current move from liquid-based to tape-based bonding has resulted from concerns over the effect of VOCs on the environment. Other advantages are that tape seams are quicker to install than liquid adhesive ones, and as a factory-manufactured product, tape has a uniform thickness. The trend toward tape is expected to continue.

To meet the need for performance data on tape-bonded systems, the study conducted by the EPDM Seam Consortium will center on laboratory experimentation complemented by field inspections. The former is scheduled to be conducted in three phases at NIST's Building and Fire Research Laboratory in Gaithersburg, Md., focusing on creep-rupture testing of tape- bonded seams. In a creep-rupture experiment, a seam specimen of fixed length is stressed under a constant load over time until it separates. Better performing seams are those with longer "time- to-failure" values.

Phase I of the consortium study will determine and compare the creep-rupture responses of tape-bonded and liquid-adhesive bonded seam specimens as a function of load at ambient temperatures. Phase II will seek to understand the effect of factors associated with sample preparation (such as presence of primer, rubber surface cleanness, pressure, temperature and tape thickness) on the creep-rupture performance of tape-bonded seams (with comparisons to data on liquid-adhesive bonded seams). Finally, Phase III will be an investigation of the effect of elevated (and possibly, lower-than-ambient) temperature on creep-rupture performance.

Concurrent with the laboratory experimentation, field inspections of EPDM roofing systems having tape-bonded seams will be conducted. The roofs selected will be located in a variety of climates and have considerable age. Samples of tape-bonded seams will be taken from these roofs so that their mechanical properties can be compared to those of liquid-adhesive bonded seams.

Each of the first two phases of the study is expected to last one year. Based on data obtained, the consortium will decide whether or not to conduct Phase III. The completed study will provide the roofing and construction industry with recommendations on the general use of tape-bonded seams. It also will provide a test method and criteria for evaluating tape/primer systems, current and future.

For more information on the EPDM Seam Consortium, contact Walter Rossiter, B348 Building Research Building, NIST, Gaithersburg, Md. 20899-0001, (301) 975-6719.

An agency of the Commerce Department's Technology Administration, NIST promotes economic growth by working with industry to develop and apply technology, measurements and standards.