Zenith Roofing Services repaired a recurring leak on an Encinitas clay S tile roof where water was showing on a stucco wall below a valley. The leak developed at a roof transition where thicker shiplap decking met thinner plywood decking, creating a vulnerable area beneath the tile as water repeatedly moved through the valley over time. We opened the affected tile and valley area, removed deteriorated wood, installed new underlayment, and repaired the decking before reinstalling the one-piece clay S tile. We also corrected the valley channel. On many tile roofs, valley tiles are staggered tightly for appearance. Over time, that can restrict the water path and allow debris or heavy flow to push water sideways beneath the tile. For this repair, we trimmed an appropriate open channel so water can move efficiently down the valley instead of backing up toward the wall transition.