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Low-Slope Reroof with EPDM, continued

Wall Flashing and Corner Treatments

At roof-to-sidewall intersections, the manufacturer recommends lapping the membrane as high up the wall as possible. I was somewhat restricted in this aspect because of the tight space under the existing flashing and siding. I slit the vertical membrane to fold it around the outside wall corners and used a putty knife to tuck it as high as I could behind the wall flashing and the flashing of the stone chimney penetrating the roof (Figure 6). I wrapped a reinforcing patch of rubber around the outside corner of the chimney to provide a base for the proprietary corner seals, to be applied next.

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Figure 6. The membrane should self-flash as high up an abutting wall as possible. In this case, existing metal flashing at the chimney and sidewall restricted the vertical return. The author used a putty knife to coax the membrane into place under the metal (top). The membrane folds into inside corners; outside corners are slit to make the transition, then reinforced with a small patch of roofing material bonded over a primed surface (bottom).

Sealing corners. To seal corners and penetrations, the system uses more pliable, semi-cured EPDM. The round-cornered, rectangular corner seal is readily stretched and worked into transitional contours. Corner seals come with release strips on both sides: blue poly on the outside face and paper on the adhesive side. The poly cuts friction, making the rubber easier to smooth onto the surface. Outside corners. To apply an outside corner cover, first you fold it in half and remove one half of the release paper. Once the sticky half is folded around the wall corner and pressed into place, you remove the rest of the release paper and, working from the corner out, press the cover into contact with the roof surface. You finish up with the roller and apply a bead of WeatherBond sealant to all edges of the corner seal (Figure 7).

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Figure 7. A proprietary corner cover, made of a more pliable EPDM rubber, can be readily stretched and formed to protect inside and outside corner transitions from roof to wall (top). As with all rubber-to-rubber bonds, it's necessary to prime the surface of the bonding area first. All cover edges receive a continuous bead of system sealant, feathered while wet to knock down the ridges (bottom).

Inside corners are a little trickier. First, you remove and replace the blue poly (which makes it easier to remove later). Fold the corner cover along the slit in the release paper and remove half the paper. Then fold the corner again into quarters, sticky side out, and fit the package tightly into the corner, bonding to the roof. Then work the corner up one side of the wall, remove the rest of the paper, and work the corner onto the roof and the other wall (Figure 8). Some extra material results, which you fold back onto itself against the wall. Follow up with the roller and an application of WeatherBond sealant on all the exposed edges. It sounds harder than it is, but the available installation video shows all the details.

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Figure 8. An outside corner is fairly simple to install; trickier inside corners follow a prescribed sequence of folds to install properly. Leftover material is folded onto itself and all edges are caulked with proprietary sealant.

Cover Strips and Sealant

With all of the rolls bonded to the roof deck and all the overlaps glued, things look pretty well protected. However, for the system to be covered under warranty, proprietary cover strips must be applied to every last lap in the membrane (the roof must also have a minimum 1/2-inch slope per foot). All edges of the cover strip must also be treated with WeatherBond sealant. The 6-inch-wide cover strip is made of the same pliable material as the corner seals and is easily worked into indentations and irregularities in the roof surface and overlaps. After outlining and priming for the strips, I rolled out the cover, simultaneously pulling back the clear poly release liner, and gave the strip a vigorous roller treatment (Figure 9). I left the bottom 1/4 inch of the aluminum drip edge uncovered to allow for an application of sealant to the cover edge later, to prevent water from backing up under the membrane. Working from the bottom of the roof to the top helps to keep overlaps in the proper sequence. You can snap a line to follow, but I just kept the cover strips centered on the overlap by eye with good results. Overlap splices in the cover strip by at least a couple of inches.

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Figure 9. Perimeter drip edge and all membrane seams are covered with a cover strip, made of the same pliable material as the corner seal (above). Sealant, applied to all exposed edges of the cover strip, completes the job (right).

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To seal the old continuous aluminum wall flashing to the roof membrane, I first applied a heavy bead of the proprietary sealant, following under the long edge. I bedded the flashing in the sealant and nailed the edge to prevent it from lifting. There was some residual tar on the flashing, the worst of which I had already scraped off, but the cover strip will adhere to hardened tar. I prepped the flashing with primer and installed a cover strip over it, rolling it firmly into place. At the chimney, I applied a liberal bead of sealant behind the flashing, then pressed and shaped the existing lead flashing back into it. To finish the job, I caulked all edges and overlaps of the cover strip with WeatherBond sealant. While the sealant was still wet, I feathered it out, using a scrap of the membrane. With EPDM in my bag of tricks, you won't catch me mopping tar on a half-lap roll again, or fighting the losing battle of trying to keep the sticky black stuff off my hands, hammer, and light-colored roof surface. Rick Stacyis a builder and remodeler in Bergen, N.Y.