Living in the Pacific Northwest grants us access to amazing landscapes, lush green forests, beautiful mountains and gorgeous coastlines. For our roofs, though, it comes with a price. Moss. Proud of that 30-40+ year asphalt roof you paid top dollar for? You should be, it’s a beautiful product and adds value to your home. But, do you know how to care for it when it comes to moss growth? Moss grows slowly and therefore we don’t really notice it as readily as say… a leaky faucet in the bathroom you use daily.
There are many ways to retard the growth of moss on your roof; zinc detergents, zinc strips, baking soda, bleach, power washing, etc. I’m not here to talk to you about the different ways to keep off moss. I’m here to talk to you about the two items listed above that do more harm than good.
Lets begin with Zinc. An element. Something that is already in it’s purest form and does not break down. The zinc is toxic to moss and thus, works brilliantly. However, an Oregon State University study found zinc is also toxic to fish and other aquatic life downstream. Going as far as to say “Though this product is supposedly safe for surrounding plants, it is toxic to fishes and aquatic invertebrates. Do not apply this product to water or let the product come into contact with water sources.” which is kind of hard to do when you put it all over your roof and allow rain to wash it down the drain.
One of the most common forms of moss retardant is power washing. While the immediateness of the results and the profound visual difference power washing can have could cause a person to think it’s a good idea… it’s not. Time and time again I find myself on the roof of a house that has been put-up for sale, snapping picture after picture of pressure-washer damage. Your roof, while able to resist the constant impact of the elements, can not resist a hard, directed, pressurized jet of water pointed directly at it. Bundle this with the fact that moss has been compromising the roofs integrity for years as it was allowed to develop and you’ve got a recipe for disaster.
In conclusion, when considering moss remediation and removal, it’s important to take into consideration the which types align with your desired result. There are zinc strip products that claim they are non-toxic to aquatic life. There are roof-power-washing companies that say they won’t damage your roof. My advice to you? I personally chose to treat with non-toxic products that have literally zero negative side effects, like baking soda. Oh and I never, never recommend power washing, ever, seriously, ever, they’ll wreck your shi-ingles.