Why is the flashing at a roof-to-wall junction checked at its lower termination in particular?

Flashing along a roof-to-wall junction gathers water for the whole length of the run and delivers it to the bottom, so the lower termination handles the accumulated volume of everything above it. That makes it the point of greatest hydraulic load and the point where a detailing error has the greatest consequence. It is also the point most often done wrong: the last step flashing left short, no kickout to turn the water into the gutter, the counterflashing stopped before the end, or the water simply released against the cladding. The visible consequence is not on the roof at all but on the wall directly below, where staining, blistered finish, soft sheathing and eventually framing decay accumulate over years without any interior sign. That is why an inspector reads the junction from the top but examines the bottom closely, and probes the wall beneath it.

Water collected along the whole junction is discharged at the lower termination, so it carries the greatest volume and a detailing failure there does the most damage.

Step flashing along a roof-to-wall junction conveys water downslope to its lower termination, where a kickout diverts it into the gutter. Failure at that point drives water into the wall assembly, causing concealed decay.

It All Arrives at the Bottom. Everything the junction collected shows up at that last piece of flashing.

The missing kickout is the specific defect to look for at that point, and stained or soft cladding below is the confirming evidence.

• •Checking the flashing run without examining its termination
• •Not probing the wall below the lower end
• •Assuming no interior evidence means no damage