Moss Control is the best way to keep moss from growing on your composition roofing material. Moss control can be applied in various ways to pretty much year around in the Northwest. Many times we are called out when the moss has already established and growing out of control on the roof. We hear lots of stories of homeowners trying different products with varied success rates. More often than not, the product did not take care of the moss problem. This could be partly due to improper application rates or methods or simply product failure.
One product available is zinc strips theoretically the rain flows over the zinc strip releasing a small amount of zinc down the roof and repelling any moss that might try to grow. There are a couple issues with zinc strips that consumers should be aware of, firstly the roof needs to be free of moss prior to installation. The typical life of a zinc strip is 3-5 years and it will protect approximately 1-3 ft below the strip. As you can plainly see in the photo to the left this zinc strip has failed. Not only is moss growing right underneath the zinc strip, but there are many nail holes along the ridge line. In our experience for zinc strips to be effective they need to be placed every 3-5 ft down the roof and replaced every 5 years. This of course would look obscene, and more importantly create many holes in the roofing material giving water a chance of entering the home. Composition roofs have a small thin tar strip on the backside when warmed up will melt to the next layer creating an impenetrable layer of protection. Any puncture into the roofing material is a invitation for a roof leak. If you would like more information just give us a call (503) 844-6500 or fill out the Contact Us form in the upper right hand corner.
What about Chlorine Bleach for moss control?
What about chlorine or bleach for moss control? Bleach will kill moss, in fact ARMA (asphalt roofing manufactures association) does state that cleaning 
with a mild bleach solution will work to clean composition roofs. You can read the ARMA Technical Bulletin here. More importantly, this can be used to clean mold and mildew in the proper proportions. But bleach is corrosive, bleach does stain things very quickly and will kill anything it touches unless plenty of water is used to dilute it. Bleach can ruin siding, decks and any sort of cloth material. I have yet to see one gutter system that doesn’t have some leak in the corner. Bleach is a poor moss control agent because it doesn’t last very long, 4-6 months before moss starts growing again.
In many parts of the United States black roof stains or Gloeocapsa Magma is more prevalent than moss. In most cases, moss is really the bigger problem in the Northwest. While roof cleaning with bleach will work, there are better options out there if moss control is the main concern. Mixing bleach and a moss control agent such as zinc is a very bad idea and gives off poisonous fumes. Please keep that in mind if you are attempting to try and clean a roof, or are performing routine moss control maintenance. Also, please keep in mind ladder safety, many moss control professionals fall off ladders each year. If you would like more information just give us a call (503) 844-6500 or fill out the Contact Us form in the upper right hand corner.
Would you like more information on moss control?
If you would like more information on moss control, or would like a free evaluation just give us a call (503) 844-6500 or fill out the Contact Us form in the upper right hand corner. In most cases we can give you an estimate right over the phone and provide you with any information needed to help in your research process.