Rotten eaves and damp roofline

Here we found the tile head lap too short and along with an execessive moss buildup (retains moisture and blocks egress of rain water) combined to speed up the rot of the under tile felt (some times called sarking). The tile lap was rectified, continuous vents fitted along eaves and eaves support trays fitted under the old felt (in most cases cutting back of felt would be best and an insert of new material fitted would be best). The tiles refitted after a good clean.