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Penetrations and Edge Details Weatherproofing roof penetrations is straightforward with EPDM as long as you work carefully and follow the rules. The secret is to use uncured EPDM, which comes in narrow rolls designed for patching and flashing applications. Cured EPDM has a memory; when you stretch it, it springs back to its original size. Uncured EPDM has no memory; when you stretch it and glue it around a vent pipe, for instance, it forms itself to the shape of the pipe (Figure 3).

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Figure 3. Uncured EPDM flashing membrane molds easily to roof penetrations like metal chimneys (top) and plumbing vent pipes. All flashing patches should be sealed with a fully glued double layer of EPDM (bottom).

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Patches require two layers of flashing membrane — a smaller first layer and a wider top layer that completely covers the bottom layer. For plumbing vents, you can use an EPDM rubber boot instead of the first layer of EPDM. Patches and flashing are glued with splicing adhesive. Where the roof meets an inside corner of a sidewall or parapet, you can either fold the corner or slit the membrane and patch (Figure 4).

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Figure 4. At outside corners, slit the membrane and apply a two-layer patch of uncured flashing membrane (top). Inside corners can either be slit and patched like an outside corner, or folded and secured with a termination bar (bottom). At outside corners, a patch is always necessary. Where a roof meets a brick wall, you glue the EPDM to the brick for 8 to 12 inches up the wall, then secure it with an aluminum termination bar (Figure 5). Figure 5. Use aluminum termination bars to secure the edges of an EPDM roof. A special lap caulk protects the top of the termination bar, while a water-block tape or mastic seals the bottom edge of the membrane. Where an EPDM roof meets a wood-sided wall, you can run the EPDM behind the bottom course of siding. There are a variety of ways to detail roof edges, depending on the look you want. Your EPDM supplier can provide detailed installation specs and drawings. Joe Bublick is a roofing contractor and builder in Toledo, Ohio. Photos by Carolyn Bates and courtesy of Evergreen Roofing.