Yes, you should clean your terracotta roof routinely. One of terracotta roofs' chief appeals is that they are aesthetically pleasing. However, they are perfect for moss and algae growth, and these growths can greatly reduce the appeal of your terracotta roof. Terracotta roofs are perfect for moss growth because they are porous, and there are several damp, dark nooks and crannies between overlapping tiles that favor moss growth.