I have always commented in my inspection reports on the termination of upper roof drains at lower roof surfaces. The theory is that directing a heavy flow of water in a concentrated area will produce more wear than the rest of the roof will see.
This is in fact what will happen.
The fast moving water will not only wear the roof faster, but as the roof granules go away it leaves the asphalt more vulnerable to exposure to the sun. The sun further hastens the localized damage. The areas tend to stay wet longer too. This promotes the growth of moss which further damages the surface.
Because the vast majority of roofs are black, or very dark in color, this granular loss does not show up very well. It might even go un-noticed by the inspector--especially if the roof is wet. It is better to assume there is granular loss and then look very closely. This condition certainly cannot be seen from the ground.
At a recent inspection the roof was light in color and I got a picture of a great example of what can happen to a roof in 10 years. The “black” area (that “looks” wet) is where there are NO granules left.
The solution is to extend the downspouts across the roof to the lower gutter.
Some people would rather see the roof destroyed than have the look of the downspouts crossing the roof. However, if the section that crosses the roof is changed to a color of pipe similar to the roof covering they will be barely noticeable.
Another solution that I like a lot is to install a tray across the roof to carry the water to the lower gutter.
They look pretty good and don’t clog up.
This roof will now need to be repaired—well before its 25 to 30 year life expectancy.
Charles Buell, Real Estate Inspections in Seattle
* * * * * * * * * * * * * * * * * * * * * * * * *
PS, for those of you that are new to my blog (or for some other "unexplained" reason have never noticed)all pictures and smiley-face inserts (emoticons) (when I use them) have messages that show up when you point at them with your cursor.
WA State, Home Inspector Advisory Licensing Board