When and How Much Moss Is a Problem?

There is a consensus that growth of moss on most standard residential roofing materials (either composition shingles or cedar shingles and shakes) can damage the roof. However, there does not appear to be data showing exactly how much moss can be tolerated by a typical homeowner. NCAP recommends that you concentrate your moss control efforts on the parts of the roof most prone to moss problems. These will probably be on north-facing slopes and in the shade of trees or other buildings. Parts of the roof that get direct sun are unlikely to develop moss problems.

Prevention of Moss Problems

Prevention is roof cleaning. In western Oregon (and areas with similar climates), cleaning roofs once or twice a year, in the fall and possibly again in the spring, is recommended. Cleaning removes debris (leaves, needles, etc.) that slows drying of the roof and removes moss plants. Cleaning a roof is, at least conceptually, simple. “In most cases, anyone who’s willing to climb on the roof can wash off the material with a garden hose.” Wet sweeping will remove most of the moss, as long as plants have not gotten too well established. Getting up on a roof can clearly be dangerous and should not be taken lightly. If your roof slope is steeper than five inches of rise per horizontal foot, you will need either to hire a professional or to use professional equipment. You should start at the top of the roof and work down; otherwise you may damage your shingles. If the roof has lots of moss, you may need to use a pressure washer. Pressure washers are powerful; be sure not to damage the roofing material.

Conclusion

So what should an environmentally conscientious homeowner do about a mossy roof? Keep your roof clean and prune nearby trees. (Be careful up there!) If moss thrives on your roof, think about moss treatment after you’ve cleaned your roof, before it damages your roof, Hire a professional to help if you do not feel comfortable or safe on your roof.

6 Reasons to treat moss
• Does not look attractive
• Leads to water damage
• Home Insurance may be canceled if heavy moss growth is not removed
• Holds moisture on roof
• Lifts edges of shingles and may break tar seal
• Company and in-laws comment on mossy roof

—————————————————————

Author: Richard Lundstrom of Gutter Helmet of Oregon has provided Oregon residences with over 10 years of gutter replacements, roof cleaning, roof replacements and roof repair. He may be contacted at 503-639-7700 for more information.