Can borax be used to remove roof moss?

Borax, sodium borate, can be used to remove roof moss and is sometimes recommended as a low-cost DIY alternative to commercial moss killers, but it must be used carefully to avoid damaging shingles and plants. Borax works as a desiccant and herbicide that can kill moss when applied as a solution. A typical DIY recipe involves dissolving one cup of borax in one gallon of water and spraying it onto moss-affected areas. The solution needs to dwell for a period and then be rinsed, and dead moss can be gently swept off after it dies over weeks. However, there are drawbacks. Borax is not specifically formulated or tested for asphalt shingles, and shingle manufacturers do not recommend it, so using it could potentially affect warranty coverage if damage occurs. Borax can also be harmful to surrounding plants, grass, and landscaping if runoff is not heavily diluted, as it is toxic to vegetation in concentrated amounts. It can also corrode metal flashing and gutters if not rinsed thoroughly. More effective and shingle-safe options include potassium salts of fatty acids, zinc sulfate based products like Moss B Ware, or commercial products like Spray and Forget that are specifically labeled safe for roofs and require no pressure washing. If you do use borax, apply on a cool overcast day, avoid scrubbing shingles, rinse thoroughly with low-pressure water, and protect plants by soaking them with water before and after application.