Extend EPDM Roof Life
Remarkable as the original EPDM rubber membrane roofs were, they have evolved to address changes in application techniques and systems over time. Most of these upgrades relate to seaming, attachment, flashing, and edging. Could your roof benefit from an upgrade? These four issues with existing aged membranes offer the greatest potential benefit.
1) Seaming and T-joints. Early systems for joining side and end laps of sheets required several steps, each of which required skilled workmanship. These included wiping the membrane to remove surface talc (a release agent needed during the vulcanization step) and accumulated dust and dirt so that wet-applied adhesives would adhere to the membrane. The solvent-based adhesive was applied to the surface of the membrane and the intended overlying EPDM, then checked with a knuckle to make sure the adhesive was tacky but not wet. A steel roller was used to insure proper embedment of the membranes into the adhesive.
Today, solvent-free tape is usually either field or factory-applied to laps, replacing the wet adhesives of previous generations and insuring a more uniform adhesive thickness. With the adhesively bound seams, a pumping grade of seam caulk was applied to the exposed edge of the seam so that moisture would not infiltrate and degrade the adhesive layer seams.
In the case of rehabilitating an existing EPDM roof membrane, it is impractical to examine every inch of suspect or delaminated seams. Instead, it is recommended that weathered surfaces are cleaned for several inches on each side of all field seams and that a cover strip of fresh EPDM membrane is applied.
A T-joint, where three layers of membrane come together, is especially vulnerable to moisture penetration. For older EPDM roof systems, a target piece of self-adhering membrane can be centered over the T void during renovations to the EPDM membrane.
2) Shrinkage of EPDM roof membranes. While fully adhered and mechanically attached EPDM roofs generally resist to shrinkage over time, ballasted membranes sometimes demonstrate shrinkage at penetrations and roof perimeters.
The Midwest Roofing Contractors Association (MRCA) and later the National Roofing Contractors (NRCA) offer a step by step guide to repairing and re-attaching EPDM membranes and flashings, which will be valuable if you notice shrinkage during an inspection.
3) Restoring displaced ballast or reattaching EPDM membranes. Where roof perimeter ballast has been displaced by wind scour, add additional larger diameter ballast (assuming the additional weight is allowed). Many codes require 10 psf of #3 or #4 (nominally 1.5 in diameter) stone for the field of the roof, but you can upgrade to 17-20 psf of larger stone (2-.5 in diameter) in perimeters and corners. Alternatively, you can use pavers in these critical areas. A comprehensive document on designing ballasted roofs for wind resistance is available on the SPRI website as ANSI/SPRI RP-4.
Where adhered systems have become detached, such as delamination at the interface of the membrane and thermal insulation/coverboard, it may be possible to re-anchor everything by using a mechanically fastened system installed in an approved pattern. Fasteners or battens would then be covered with a fresh strip of membrane.
4) Repair of flashings, edgings and penetrations. Of all the changes made in EPDM systems over the years, upgrading or replacement of vertical flashings is the most dramatic. First generation materials consisted of uncured neoprene (chloroprene). It turned out that the neoprene would not only cure with weather exposure as intended, but it would also embrittle, especially on south-facing exposures.