What causes the ugly black streaks that run down a shingled roof?

Question

How can you get rid of these black streaks on a shingled roof? How do you redeem the warranty on shingles which are usually 20 yrs.?

Answer 1

Black streaks may also be coming from exposed nail heads if the shingles were improperly nailed.  As said above, this would not be covered under the shingle warranty.  It would be a warranty issue for the roofers.  Look and see if you can trace the streaks back to an identifiable source.  If it is nail heads or some other penetration of the shingles you will need to get them repaired before your roof starts leaking.

Answer 2

That is what is known as acid rain.  Call the manufacturer, I'll bet it isn't covered since they have no control over the smog in the sky.

Answer 3

The back marks you talk about are growth and can be removed easily with the right process, call the manufacture and they will explain. Keeping the roof clean is your responsibly.