Removing the Moss and Grime can truly enhance your home
Over time, a significant enough portion of the airborne dust and debris that pollutes the atmosphere with find a home at your home.
This build-up provides the foundation for growth for moss and lichen growth.
Both moss and lichen like a slightly alkaline to an acidic surface, as the combination of acid rain and alkaline tile (concrete) produces a very weak salt solution which it likes. That is one of the reasons that you see a lot of moss and lichen on houses near the sea. Both of the organisms and plants like wet conditions, therefore they tend to grow better on north facing roof slopes.
Moss is a very simple plant form that does not have a root or means to suck up or move water around inside its form. It has to absorb the moisture directly and that is why it likes damp shady places, that’s why the edges and gaps between and around concrete roof tiles and fibre cement slates/sheets.
In time, once it gets a foothold it will spread exponentially and will not stop until it’s professionally removed.
Conclusion:
Moss and lichen will grow on all roofs given time and the rights conditions which is seemingly everywhere here in Ireland. Under roof aerials is a great starting point due to the nutrients provided by the bird droppings.
It’s up to you to decide whether it’s unsightly or not but if you do decide you want your roof to be free of this algae, help is available nowadays