I'm not sure if it was here or on uk.d-i-y but I seem to recall a recent
thread where it was suggested that a copper strip or wire along the top
of the roof would do the trick.
Apparently, the metallic salts that wash down the roof when it rains
gradually poison the moss and that's the end of it.
I doesn't sound as if you are in any hurry ...
... might be worth a try?
This as been taken off their website
"Your house is probably the largest single investment you will ever make, so
it makes sense that you should protect its value."
Listen to them and don't have it done. The worst thing you can do with
tiled/slated roofs is to coat them. At 50 years old it probably is up for a
new roof anyway, spend the extra and you won't have to worry for another
50-60 years. After 40 years in the game (and waiting for 2 new knees to
prove it) I have seen some horrendous sights. At the end of the day it's up
to you though.
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