Updated: Jun 23, 2020
Going green is trendy, except when it's covering your roof. Moss can overgrow in areas that are shaded and north facing. Spreading moss quickly fills voids between shingles and tiles and can lift up roof materials. This allows rainwater and other moisture to damage the integrity of the roof.
The pros at Wilderland weigh in on popular moss killers and what to watch for to protect your wallet and your roof.
Many moss removal companies use zinc sulfate to kill moss on roofs, and it is even sold at home improvement stores under the brand name Moss Out.
While this chemical is cheap and effective, it is unregulated, and is considered a heavy metal that bioaccumulates. Since it is not regulated for roof moss removal, it is often misapplied or overapplied, adding to the toxic runoff from your roof and into the groundwater. You can tell zinc sulfate has been overused when a roof has white, powdery splotches since an effective amount shouldn’t even be able to be seen from the street.
Wilderland only uses the non-toxic and eco-friendly moss removal pH neutralizer sodium percarbonate, eliminating the problems that zinc sulfate poses to the environment and your property.
Copper sulfate is another commonly used chemical for treating roof moss. Because it is considered a heavy metal, it is not environmentally friendly, can bioaccumulate and is harmful to fish.
Some companies offer a zinc strip that they nail to the top of the roof. This solution is effective in the short term, but the strip will eventually oxidize and lose its effectiveness over time.
That leaves a strip that needs to be removed and the nail holes filled in after about three years. Wilderland techs will sometimes remove them if our clients ask, but only if we can do so without damaging the roof or leaving large nail holes.
The only treatment that works effectively in the long term is sodium silicate, which is applied as a coating to the roof, and acts as a barrier between moss and shingle. This treatment lasts for about three years with reapplication, but is cost prohibitive for most.