Tile roofs need gutters to collect the cascading rain water and lead it away from walls, foundations and fittings. Gutters are usually made of metal or vinyl and installed along the edge of the roof to lead the water to the ground through a downspout.
Building codes and regulations do not specifically require gutters to be installed, but demand buildings have some system of water disposal from roofs that will lead drainage away to, or below, the ground surface. They also state drainage disposal must happen at a minimum of five feet from foundation walls.
Water damage on exterior walls can lead to rot, decay and damp interior of the building. Gutters catch the water before it can settle on the walls and cause spoilage. By leading the water away from the building and its immediate surrounding, gutters prevent soil erosion that could destabilize the building's foundations. Gutters can catch sliding roof tiles and prevent them from falling on unsuspecting passers-by.
Gutters are only purposeful if properly installed and regularly maintained. Blocked or broken gutters can cause more damage than good as they will spill large amounts of water on particular spots on the wall or the ground below. Installation should include gutter guards to prevent tiles and vegetation to block the system.