Tiles That Have Slipped Out of Position: Check the Building Paper for Damage When Repairing
Lots of roofs have tiles that have shifted or slipped. Generally these tiles just need to be moved back into position and secured. One of the more common places for this to happen is where the tiles are next to a higher area / wall of the home. Roofers generally consider this a simple maintenance issue.
High winds, earthquakes and storms
Roofs may incur tiles that shift or move when bad weather hits. Even small earthquake trimmers or sonic booms from jets can cause tiles to shift. It is not a bad idea to check your roof tiles after an earthquake or a bad windy storm.
Remember, maintenance of a roof should be considered part of home ownership.
Check the building paper under tiles that have slipped out of position
When placing tiles back into the position they were in before slipping, the building felt or paper under the tiles should be checked for damage. The reason for this is that it is basically the building paper under the tile that provides the majority of water proofing of the roof, not the tile. The tile serves to protect the building paper or felt from UV rays or physical damage from wind and other weather elements.
If the building paper under the tile gets ripped or damaged when the roof tile shifted or moved, then the roof may leak, even if the tile are placed back into position.
Who to consult? Roofers and qualified handymen.
Home owners and handymen often do limited maintenance and repairs on their roof. Roofers do the same as well as "Tune-ups."