Some things are inevitable.
Every time I watch a movie called Titanic, the ship always sinks. Just the other day, I caught the 1997 version of “Titanic” about midway through the movie. Even though I’ve watched this same film about five times, albeit in portions, I still held hope that maybe the ship wouldn’t sink this time. But it did. You would have thought Captain E.J. Smith could have avoided that darn iceberg, since it hadn’t moved in 20 years, while Leonardo DiCaprio still managed to slip into the frigid ocean waters and die, after once again failing to find a half decent floatation device to support both he and Kate Winslet.
Spring and fall in our part of the world means our local weather reporters need only to remember three words when describing what atmospheric conditions we all have to look forward to in the morning, them being “wet and cloudy”.
If you own an asphalt or cedar shake roof, then persistent wet and cloudy conditions will lead to moss and algae growth, it’s inevitable. Moss and algae are basically plants. As a result, they require everything a plant needs to survive, including plenty of water, relative shade, a sprinkle of sunshine, and a reliable food source, or basically, the exact environment provided by the average roof in any one of our three united counties. Moss and algae differ from regular plant life in that they have no roots. However, they stick really well to practically any non-metallic surface, and once established, will do what plants and all living organisms do, and that’s multiply. Moss and algae are basically esthetic issues, whereby in mild cases, their appearance is worse than their bite. However, if allowed to persist, moss will grow in between the shingle tabs, loosening the necessary bond between these tabs, creating a path in which water could infiltrate into the plywood below.
When that happens, you get a roof leak, with the only solution to this problem being total roof shingle replacement. Unfortunately, knowing why moss exists on our roofs, doesn’t make avoiding or preventing it from happening any easier. The problem is the huge iceberg, which in this case represents our very accommodating environment. Temporary solutions to eliminating moss are those related to either cleaning or scrubbing the moss off the roof. The same type of bleach, ammonia, or regular home cleaning soaps that would be effective in cleaning mold, would be effective in removing moss. Roof, siding, and deck cleaners are also available on the shelves of your local building supply centers. The only issue of course is that your moss problem is situated on a roof, which is not only sloped, but has a granular surface that could become loose with basic foot traffic. Slope plus loose granular surface plus a 16-24 foot drop that leads to a sudden stop equals not having to worry about your moss problem anymore.
So, unless you own the same type of roof harness worn by professional roofers, I recommend avoiding that climb up the extension ladder. Besides, cleansers can be a little harsh on your plant and garden beds below.
What about pressure washing? Bad idea. Pressure washing from ground level will separate your shingle tabs and drive water underneath, basically achieving in minutes what will take your moss years to accomplish. Pressure washing from above is also not recommended because you’ll loosen the granular surface, again, aging your roof unnecessarily. Essentially, you’ve got to melt the iceberg, which means changing the environment. This can be accomplished by installing a strip of zinc banding just under the roof capping, or first row of shingles near the peak of the roof. Perform this task in warm weather, enabling you to more easily bend back the shingle tab. When it rains, tiny particles of zinc get washed down over the shingles. Zinc is poisonous to moss and algae, so in time, the moss will loosen up and fall off. Good moss fighting.