On Sunday, 22 December 2019 17:29:27 UTC, Mr Pounder Esquire wrote:
Bungalow, back end south facing. I was unhappily on the roof about 5 years
ago scrapping and brushing the moss off. The tiles are very rough and are
like steel.
I'd read that stringing a length of copper wire over the ridge kills moss,
so I did it. The moss returned on the back end of the roof, never mind and
******** to it, I'm not going up there again. Since Autumn chunks of moss
have been falling down almost every day. Maybe the copper wire takes time to
work?

http://www.ibnature.com/copper-compo...lgaecides.html
https://homeguides.sfgate.com/copper...oss-33916.html