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Low-Slope Reroof with EPDM, continuedMain course. We followed the same sequence to install successive rows of roofing: Snap a guideline at the center release mark, remove the lower release liner, broom the membrane into place, then slide the upper release liner out, leaving the 4-inch-wide release liner at the overlaps temporarily in place. For economy of motion, I chose to install the membrane horizontally, rolling it directly from one end of the roof to the other, despite the fact that once it passed over the hip, the membrane ran parallel to the watershed off the roof. Either orientation seemed okay to me, as the overlaps would all be glued and sealed. Arguably, the vertical direction has an advantage, in that water shedding off the roof won't puddle behind any horizontal laps. We applied a stock aluminum drip edge around the roof edge for aesthetics and to direct runoff into the gutter (Figure 3).


Figure 3. A standard 2 1/2-inch-wide aluminum drip edge is installed over the membrane to provide a clean-looking perimeter and direct water into the gutter. An EPDM cover strip will be applied later to seal the material transition.

Sealing overlaps. When a roll ends short of the end of the roof, an overlapping seam of at least 4 inches is required. Before bonding the seam, you have to apply proprietary adhesive primer to the overlap area, using a clean cotton rag, and allow it to dry completely, which takes 5 to 15 minutes. It's a good idea to outline the overlap area with a pencil first to guide the primer application. After the primer dries, remove the release liner and fold the lap over into place (Figure 4), removing just enough of the 4-inch release strip at the bottom edge to allow full-width adhesion of the lap joint. To ensure a solid bond and remove any air bubbles, all laps must be thoroughly worked with a hand roller across the joint, end to end. The best tool for the job is a heavy-duty, steel hand roller.


Figure 4. Splices in a course must be prepared with a proprietary primer before joining with a minimum 4-inch overlap. Peeling back a short length of the separate 4-inch-wide parting strip along the bottom edge allows full-width bonding of the splice.

Of course, the overlaps between courses have to be bonded together. Where the upper layer of roofing laps the lower, trace the overlap area with a pencil, apply primer, let it dry and press the lap into place, while progressively pulling the 4-inch-wide release liner away (Figure 5). When a course overlaps a splice in the course below it, I apply a bead of WeatherBond sealant to the edge of the splice and bed the upper lap into the uncured sealant.


Figure 5. With all of the courses installed, the author goes back and prepares the overlaps with primer before peeling off the 4-inch-wide protective strip and bonding the edge. A vigorous follow-up treatment with a wood or steel seam roller assures a good seal without bubbles or blisters.