Blocked Valley Flashing

Roof valleys are designed to catch storm water runoff from two adjacent slopes of the roof and direct this runoff over the roofs edge.  Far too often, the bottom of the valley is blocked by edge tiles.  I suppose these tiles are installed over the bottoms of the valleys in order to improve the cosmetic appearance of the roof. However, this appearance is soon diminished by the deterioration of the fascia board due to water penetration from every rain.  Properly installed valley flashing extends beyond the edge of the roof and the edge tiles.  This installation can be accomplished by cutting slots in the bottom edge tiles so the flashing can extend thru the tiles or holding the bottom tiles back to the edges of the flashing.  The metal flashing should be visible at the bottom of every tile roof valley; otherwise, it is improperly installed.