How to Make a Kick-out Flashing Diverter for the Roof

​In the case that a shed or gable roof butts into a wall, one challenge is to ensure that water running down the roof at the roof-wall intersection ends up in the gutter. Otherwise, water can seep into the wall below the gutter.

The simplest solution is a kickout diverter flashing, which serves as the bottom piece of metal step flashing. It's placed over the membrane at the eave and bent to serve as a spout, directing water into the gutter. The minute or two it takes to create this detail has a pretty big return on investment. But it's often left out.

What happens if you forget the diverter?

If water is able to get behind the trim and siding below the gutter, the consequences can be disastrous.

"Water flowing down the wall from that intersection will rot out the sheathing in the shape of a cone, and the rot area will be six feet wide at the base of the wall," says Dan Burke, owner of White Wolf Construction and Home Inspection in Columbia, Missouri. He has found problems on homes just a few years old. "The last one we fixed was an 8-year-old house with about $50,000 worth of damage."

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Sometimes an architect will object to the way the kickout looks. An alternative suggested by Bill Rose, author of "Water in Buildings: An Architect's Guide to Moisture and Mold," is to install a pressure treated 2x4 at the roof-wall intersection before the roofing or siding goes on. Then bend flashing over the 2x4 and down onto the roof. When it's time to install the siding, the flashing will already be outboard from the cladding allowing water to drain straight into the gutter.