Case 3: EPDM Roofing Membrane Installation

We investigated the failure of an ethylene-propylene-diene rubber (EPDM) (ASTM D4637-10 [6]) roofing membrane and assembly. Approximately 1.5 years after roofing membrane installation was completed, building maintenance per­sonnel observed detached roofing membrane.

During our field work, we determined that the typical roofing assembly con­sisted of, from exterior to interior, black EPDM roofing membrane adhered with an unidentified manufacturer’s bonding adhesive; paper-faced polyisocya – nurate insulation boards applied in one 2.5 in. (6.35 cm) thick layer, adhered with an unknown foamed adhesive; and a concrete roof deck of unknown thickness.

During our investigation, we made a total of ten sample openings. At five of ten sample openings (50 %), we noted moisture and apparent microbial growth within the roofing assembly. At several of these openings, we noted cohesive failure of the insulation board facer and adhesive failure of the EPDM mem­brane. Our investigation was focused on installing relative humidity probes to monitor the concrete roof deck moisture content. We measured the temperature and relative humidity of the concrete topping slab using a modified version of ASTM F2170 [5] (we had to limit the time between readings due to facility con­straints). After 3 h, the relative humidity of the concrete roof deck at the wettest location was 98.9 %.