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Installing Drip Edge on a Humpy Old Roof

November 20, 2015

Dealing with dips and making clean overlaps

Metal drip edge flashing is installed on the perimeter of a roof to direct water away from the fascia, into the gutters, and to keep wind-blown rain out of the assembly. Even though it is a flashing, it is also finish work, so details matter.


Installing drip edge flashing on a humpy old roof is just like installing it on a new roof. Only different.

There’s no telling what carpenters 75 years ago were thinking.

In this case they didn’t think it was too important to fill in the rest of the roof sheathing.

As Lynn was doing that, he discovered that they also didn’t worry too much about humpy rafters.

The shingles will ride over the hump, but the edge metal will buckle.

To fix it, Lynn cuts the top flange of the flashing allowing it to overlap and smooth out the bump.

The drip edge will be covered with a strip of peel and stick roofing membrane, so the overlap is not a leak concern.

The more common seam with drip edge is the overlapping individual pieces. If you overlap them the wrong way, the seam will be visible.

And overlapping the flashing pieces can build up the profile attracting more attention to the seam . To get a cleaner overlap, Lynn cuts the leading edge off the outer piece for the distance of the overlap.

The overlap direction should be opposite the direction of view.

Now, when the two overlap the joint is clean.

The last piece extends to the end of the eave and is covered by the drip edge running up the roof slope.

With the eaves and rakes covered, Lynn adds a strip of roofing membrane to seal the drip edge against water leaks from wind-blown rain and ice dams.

—Lynn Hayward is a builder and remodeler in Northport, Maine

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