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).
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
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).
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
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).
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
Joe Bublick is a roofing contractor and builder in
Toledo, Ohio. Photos by Carolyn Bates and courtesy of Evergreen