Terracotta roofs can be effectively cleaned making them look brand new. It can be safely done without doing damage to the roof. Much like slate roofs, terracotta roofs are durable and can provide decades of reliable service.
Cleaning Terracotta roofs can be very tricky for a number of reasons. One is that the surface of the tile is pourous, giving mold and mildew a good hiding spot from the cleaning solution. Another reason is that the tiles are easily cracked if too much weight is placed on them. Pressure washing is not required in order to clean terracotta roofs. Since terracotta often has a multi tone coloration, the results vary, but the roof goes back to the original color prior to the staining.