I have green moss growing on my sidewalk, front wall, steps, and the house wall behind some plants.
A 50% dilution of regular household bleach kills the stuff on the sidewalk, steps, and front wall. Spray it on, wait half an hour, hose it off. The part that doesn't disappear (in the cracks) turns a shade of yellow which I presume means that it's dead and some sweeping and scratching will remove it.
I'm loathe to use such a powerful mixture on the house wall because the run-off will go all over the plants and even if I cover them it'll end up in the soil possibly killing them (I think). I've tried (gingerly) a 10% solution but that didn't do anything. The wall is porous limestone and is painted so it doesn't matter if the mode of killing causes a stain. I'll repaint it anyway. Does moss require oxygen to live? If so would painting it with shellac do the trick? Is there some other appropriate chemical that will kill the moss but not the plants? BTW the plants are a yew tree and an azalea if that makes a difference.