What stops it being washed off the roof?Also have a look at treating the roof to properla fungicide sealer. Works a treat. And it won’t grow back.
I'm not convinced. Have you got any 10 year old examples?The product penetrates the tile and seals it. Nothing can then attach its self to it not even rain. Go to there web page properla, German engineering at its best.
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local