The damp weather in the UK can have an adverse effect on roof tiles as they become more porous with age. Over time this can create the perfect conditions for moss, algae, and lichen to grow on the tiles. The worst thing that can happen hear is moisture is absorbed by the tile overlaps, leading to weak points that could result in water penetrating into your loft space. Being proactive with roof cleaning services can be significantly less expensive that roof repairs or replacements.