Case 2: CSPE Roofing Membrane Installation

We investigated the failure of a chlorosulfonated polyethylene (CSPE) roofing membrane at three roof surfaces of a facility. Approximately one year after roof­ing membrane installation was completed, building facilities personnel observed inflated and detached roofing membrane and an irregular roofing sur­face from displaced insulation below the membrane.

During our field work, we determined that the typical roofing assembly consisted of, from exterior to interior, white CSPE roofing membrane, reportedly adhered with a one-component bonding adhesive; multiple layers of paper-faced polyisocyanurate insulation that varied from 2.5 to 7.5 in. (6.35 to

19.5 cm) in total thickness, reportedly adhered with a one-component foamed adhesive or a two-component polyurethane foamed adhesive; an approximately 3 in. (7.62 cm) thick composite cast-in-place concrete roof deck; and a steel roof deck with 3 in. (7.62 cm) deep flutes. We observed notable insulation board de­formation reflected through the CSPE membrane prior to our making any sam­ple openings. We made 30 sample openings in the roofing assemblies and noted the following:

• As we peeled the membrane from the insulation, we noted cohesive fail­ure of the insulation board facer at 25 of 30 sample openings (83 %) and adhesive failure of the CSPE membrane at 17 (57 %) of the openings. Some openings exhibited both cohesive and adhesive failure.

• At 14 of 30 sample openings (47 %), we observed moisture on the insula­tion board facers; we verified dampness or moisture with moisture – sensitive paper.

• At 16 of 30 sample openings (53 %), we observed staining on the insula­tion board facers.

• At 15 of 30 sample openings (50 %), we observed apparent microbial growth on the insulation board facers.

• At six of 30 sample openings (20 %), the insulation boards were dis­placed below the CSPE membrane prior to our making our exploratory opening.

• At seven of 30 sample openings (23 %), the insulation boards were deformed (typically bowed or curled); at some openings, the edges of the insulation boards were curled up and no longer adhered to the insu­lation below.

We tested five insulation board samples in accordance with ASTM C1616 [4] and calculated that the insulation moisture content ranged from 3 % to 42 %, with an average of 10 % (i. e., the samples ranged from slightly wet to very wet).

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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), and after 4 to 48 h the average rel­ative humidity of the topping slab was 73 % (relative humidity ranged between 66 % and 85 %). We used these data to develop a hygrothermal model.