Gordon, the roofers who were originally tasked to take on my roof spoke of a treatment applied with a watering can that they would apply when the moss had been removed and guarantee the roof to be moss free for four years...! Whether that chemical might have been Hypochlorite or not I have no idea.
Given the amount of effort involved in the moss removal I did think that some sort of sealer would be beneficial for sure. I have also seen roofs painted, though whither the paint has any direct chemical qualities relative to algae or moss prevention.. I have no idea.. but if Graham1s neighbours have enjoyed 8 moss free years so far ...hmm..?
