Apart from the obvious aesthetic benefits to a clean roof, there are many more serious reasons why you should remove build up from your roof:-

• Moss, algae and lichens on your roof absorb and retain water.
• Weight on the roof is increased as water weighs 1 tonne per metre cube (m3). This stresses the roof and supporting structure.
• Damp battens and roof structures under increased load will eventually buckle and warp. This can be clearly seen on some buildings.
• Roof tiles constantly wet eventually become porous
• Wet tiles splinter and break when subjected to frost
• Wet sand and cement mortar will splinter and break
• Roof tiles, ridge, hip and bonnet tiles can become dislodged.
• Damp battens and roof structures start to deteriorate through damp rot, dry rot etc.

This all means water penetrates the roof space and causes damage!