Roof cleaning is important because when left unattended, the build up of moss, algae, leaves and other debris can trap moisture and damage your shingles. This can lead to leaks and more significant damage as time goes on.
It partly depends on your environment, but a general rule is that you should have your roof cleaned once a year to avoid the build up of debris. If your roof is newer and you don’t live near many trees or other sources of debris, you may get away with once every two years.
Pressure washing is very likely to damage your asphalt or tile roof by causing shingle granules to become dislodged. Metal shingles, however, can take light pressure washing without incurring damage.
Having your roof cleaned once a year should be enough to remove the buildup of debris that causes damage, thereby extending the life of it.
Clogged gutters can cause a backup that flows onto your roof, accelerating the damage to both your roof and potentially your gutters if left alone.
If you’ve got trees hanging above your roof that drop debris, you can do your roof a favor and extend its life by trimming them.
The short answer is yes. Moss is very good at trapping moisture, which can lead to mold growth, then leading to leaks or roof damage, at minimum. Moss growth can also dislodge the shingles over time, making your roof more susceptible to leaks.