With both methods of cleaning we will not cause direct damage to your roof, we follow strict methods and procedures to ensure this. However, if there are any compromised tiles i.e. spooled tiles, cracked or missing tiles, weak or loose flashing and mortar etc then these will be exaggerated in the clean. It is very common on a moss-covered roof to have some sort of damage caused by the moss build up which then becomes evident once the clean is occurring because up until then the moss was acting like “glue” holding the tiles in position.