EPDM Roofing Solution for High Square Footage

By Rick Brown • February 20th, 2012

Since the 1960’s, an increasing number of manufacturers, building owners and contractors have searched for an alternative to the fumes, flame and expense of conventional “hot applied” roof systems. One of the original single-ply systems to provide that alternate is a synthetic rubber known as EPDM.

Ethylene Propylene Diene Monomer or EPDM, is a compound whose principal components are ethylene and propylene. This form becomes a flexible rubber when diene is added. EPDM is classified as a thermoset membrane, meaning it is cured prior to installation. The uncured form is used as flashing material and cures during the natural weathering process. Seams are chemically welded with solvent borne adhesives or specialty seam tapes with adhesive primers.

One of the early appeals of EPDM was the relatively low materials cost. The membrane is typically 25 per cent-30 percent less expensive than modified bitumen and half the cost of built-up roofs. The uncured flashing materials and lap adhesives tend to drive the price higher, however the overall cost can be considerably less than conventional roofs and this is especially attractive for large scale distribution centers or manufacturing plants.

Three choices are available in EPDM system design:

  1. A mechanically attached system with fasteners through the laps and into the substrate;
  2. A fully adhered system glued to either suitable insulation or substrate and
  3. A loose laid or ballasted system, fastened only at the perimeters and penetrations with either pavers or stone holding the system in place. As of the revised 2004 Florida Building Code, system 3 is no longer applicable in the state, but is used extensively in large facilities requiring less stringent wind uplift standards due to its extremely low installation costs.

As the early EPDM systems aged, several issues became apparent. First and foremost is shrinkage. Most notable is ballasted systems, shrinking membranes displace gravel, can distort wall or edge flashings and will ultimately tear the membrane itself allowing water intrusion. There are no universal methods of addressing shrinkage as the repairs required range from minor tension relief cuts to complete re-roofing. The second problem is lap failure, often due to shrinkage or improper adhesive installation. The latter problems have been addressed with the advent of seam tapes providing more uniform lap strength.

If your property is currently covered with an EPDM system, please contact All Area Roofing & Waterproofing for a free evaluation with maintenance recommendations..

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