Bonus on deck: a pressure-wash rainbow (Photo: Flickr/Patrick Shusta)
Q: We have green mossy stuff growing on our aluminum siding and deck. Should I power wash it?
A: You can power wash the deck, but you have to be careful about the siding.
For the siding, the best option would be to use the pressure washer on the lowest setting and be SURE the nozzle is angled down. You don't want to angle it up, where it could get water under the siding. If that isn't enough, then use a scrub brush with a long handle.
To get rid of the algae, I'd try just water first. The washer pressure on medium will take it right off the deck. You may need to scrub the siding. If it doesn't come right off, then use a weak household bleach solution.
-- Answer from Rick S., a construction supervisor on JustAnswer.
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