09/12/2022
https://www.facebook.com/reel/3283724468621676?fs=e&s=TIeQ9V
My first thought is why carry your mug up on the roof?
My second thought is, it seems way more probable that this was first caused by a flashing issue at either the apron flashing or step flashing or both.
When a roof plane meets a vertical wall, flashing is required to prevent water from dripping down the wall and behind/under the shingles. From this video, flashing appears to be installed incorrectly or missing completely at both the headwall and the sidewall where they meet the roof.
A gutter discharging on a lower roof surface is acceptable and generally should not cause a roof to fail prematurely. But incorrectly installed flashing or missing flashing can cause premature failure of the roof.
If the roof was left in service longer than it’s typical life expectancy, the water from the downspout could speed up the deterioration of the shingles and erode the granules, but at that point it’s a moot point and the gutter downspout is not the defect.