Step flashing can be and should be used on any part of the roof where a vertical wall meets a slope. Flashing is made of metal and prevents water run off from going under the shingles and damaging the roof decking. This means the most essential places to have flashing is where water would have the strongest downflow onto another portion of the roof.
Installing Step Flashing
Proper Flashing at Gutters
There are several different types of flashing depending on the area they are being used in. Step flashing for example is an “L” shaped metal usually made from aluminum that is fastened to the wall on one side and placed under the shingles on the roof side. The counter flashing goes on top of the shingles and over the Step flashing and can also be called Cap or Cover flashing. It is also metal but more typically made from copper, galvanized steel, tin, aluminum or even sometimes plastic.
Step flashing keeps water out of the seams of the roof where two areas meet by directing it down the roof and away from susceptible areas. But what happens when the water hits the bottom of the roof? Without proper kickout flashing at the bottom of the roof the water would simply run up behind the gutter and even under the siding.
The purpose of the curved edge at the end of the flashing called kickout is to drive the water past the roofline and into the gutter below, protecting the roof from damages. This is a very minor expense compared to the long term risk of roof and siding rot without this piece.
No Gutter Flashing
The most likely place for water to get behind gutters from lack of kickout flashing would be near the end caps of the gutters. This is because flashing runs along a point where two spots meet at a 90 degree angle (which is usually a wall), and gutters tend to run from wall to wall with the end cap piece protecting the end of the gutter. While it is possible for water to get behind a gutter in other parts of the roof, that would not be the fault of the flashing. That would instead be caused by lack of drip edge. The drip edge runs the length of the gutter between the roof and gutter line, unlike flashing which runs the length of things like walls and chimneys.