Sodium Hydroxide based cleaners are sold and marketed as being safer for the landscaping, but sodium hydroxide is caustic and very toxic. Sodium Hydroxide is used in stripping stains and sealers off of wood surfaces such as decks and fences. Sodium hydroxide is also a very effective degreaser and is used in the cleaning of commercial kitchen hoods. Asphalt shingles are a petroleum product (i.e. grease, oil). So high levels of sodium hydroxide in a cleaning product can cause permanent irreversible damage to an asphalt shingle roof. These products generally require much more rinsing and pressure than the sodium hypochlorite cleaning solutions used by ARCA Certified Roof Cleaners and the recommended cleaning method of the Asphalt Roofing Manufacturers Association (ARMA). The rinsing process is not only time consuming, but it can also be potentially damaging to the roof if not done correctly. A sodium hydroxide based cleaning product requires more than normal garden hose pressure to effectively rinse an asphalt shingle roof and some granule loss should be expected.
Be sure to ask your roof cleaner what the main active ingredient is in their cleaning solution before you hire them.
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