Cleaning Pacific Northwest Moss From Your Roof

Cleaning Pacific Northwest Moss From Your Roof

Moss is beautiful here in the Pacific Northwest.  It clings to rocks, creeps up decaying logs, and gives an earthy, magical quality to trees in the forest.  However, moss is not beautiful clinging to the asphalt shingles on my roof.  At first the damage from moss on the roof is minimal, but it does eventually break down the fibers of the shingles and limits the lifespan of the roof.  So, a little maintenance goes a long way.  There are many different methods online for getting rid of the moss and keeping it away, but the bottom line is that moss is acidic; it cannot live in an alkaline environment.  It also cannot live in direct sun.  After doing a little research of my own, I have compiled a few options for the do-it-yourself home owner wanting to tackle that green roof problem over winter break - which is the very best time of the year to manage mossy outbreaks. 

Trim it Up/ Clean it Out:

Take out trees and branches that overshadow your roof during the cool rainy season.  Also, keep debris cleaned out of your gutters and from the roof itself.  Debris encourages moisture and eventual moss growth.

Pros:  there are no costly chemical treatments involved, and this process is important no matter what method you use.

Cons:  some roofs accumulate moss because of directional shading rather than from tree shade, so this would not always be a complete solution.

Bleach and Water:

Spray a 50/50 mixture of bleach and water on the moss affected areas on a dry day.  When the moss dies off, scrape with a wire brush or stiff broom.

Pros:  immediate remedy, inexpensive.

Cons:  not a permanent solution as the mold will probably grow back again the next year.  Yearly maintenance required.  Bleach water can also kill bedding plants near the roof runoff area.  To minimize the plant damage, you must cover your plants or spray them down with water prior to treatment. 

High Pressure Hose:

Use a high pressure hose to spray the roof in a downward motion loosening the moss and other debris from you roof.

Pros:  no harsh chemicals to damage bedding plants.  Revitalizes your existing shingles

Cons:  can loosen or damage the shingles if not done properly.  Not a permanent solution - yearly maintenance is required.

Zinc Sulfate/Zinc Chloride Washes :

A number of chemical products are available on the market to destroy moss and discourage future growth.  These chemicals can be bought through building supply stores in your area. 

Pros:  highly effective at killing off moss growth and sometimes protecting for more than a year.

Cons:  highly toxic to the environment and measures should be taken to protect runoff areas, especially bedding plants and ponds.

Fatty Acid Soaps:

Spray fatty acid soaps such as Safer Brand Moss and Algae Killer onto affected surfaces on a dry day when rain is not expected.  Scrape remains of moss from the roof with a wire brush or stiff broom.

Pros:  organic solution that is safe for the environment - can be used for lawn moss as well.

Cons:  not a long term solution, yearly maintenance required,  and it is expensive.

Zinc or Copper Strips:

After you get the moss off your roof you can keep it off for many years by placing either a zinc or copper strip on your roof that leaches the metal up to 15 feet onto the rest of your roof discouraging moss growth.  Watch this video from a This Old House episode on how to install it.

Pros:  long term solution that prevents future moss build up, a fairly inexpensive solution.

Cons:  while the zinc or copper stripping remains fairly local on the roof, over time it can cause problems for wildlife and plant life in the runoff area.   *This is a preventative and will not kill moss already on the roof.

Baking Soda:

Sprinkle baking soda on the moss just before a light, drizzly rain.  Scrape off dead moss debris with a wire brush or stiff broom in a few weeks.

Pros:  inexpensive, safe for the environment

Cons:  not tested, therefore not an approved solution, though many locals tell me it works.  not a permanent solution.

Whatever method you use, be careful up on that roof!  If you are unsure of your balance or you have multiple stories, perhaps it would be best to hire in a professional.  These guys harness in and have the proper equipment to get the job done safely and effectively.  Be sure to ask about environmentally safe solutions.

Cari Schwisow Headshot
Phone: 360-878-5401
Dated: December 21st 2011
Views: 11,168
About Cari: I am pleased to be with RE/MAX Northwest, a highly respected and innovative real estate firm in Olym...

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