Kick-out flashing, which directs roof runoff away from a sidewall and into the gutter, is one of the most important and most ignored pieces of flashing on houses. The rotted sheathing shown in this photo (1) extended all the way to the foundation—the result of one missing kick-out at the roof-wall intersection above. In new construction, it's typically the roofer's job to install the kick-out with the step flashing, and the sider's job not to screw it up. However, when a roof gets replaced, there's only one trade on the job, and it remains a detail that some roofers don't want to deal with. It's a pain.
What makes kick-out flashing particularly difficult to retrofit is the diverter needs to be large enough to redirect the water. The diverter crosses the siding at an angle, and often there's no easy or particularly handsome way of cutting into the siding at an angle. Some sidings work better than others (2). Wide-panel vinyl is one that is particularly troublesome, as the cut will take a bit out of only part of the panel and it's easy to crack the remain part. There's a tendency to "go small" with the diverter (3), but wimpy won't work. Water will just spill over a small diverter and soak the wall, rendering all efforts useless.
Mark Parlee, a siding-replacement contractor and building inspector in Urbandale, Iowa, devised a nice technique that uses a trim board along the rake of the roof (4) with performed Dryfleckt kick-outs. While Parlee adds this detail to his siding-replacement jobs, it can be done by the replacement roofer, too, by snapping a line parallel to the rake and cutting out the siding. This detail has the benefit of making the step flashing a lot easier to replace as well.
