01
Document the location safely
Photograph the obstruction from the ground or another safe accessible location and note nearby trees or roof features. Tell the roofer if the accumulation is recurring. Do not walk onto slate or push tools across the roof to clear it. Debris removal should be planned so it does not damage the valley metal or surrounding pieces.
02
Ask why it keeps returning
After cleaning, request photographs of the exposed area and any defects found. Discuss whether surrounding vegetation or an adjoining roof contributes to the buildup. A clean valley may still need assessment if corrosion, displaced slate, or damaged details are visible. Keep cleaning and repair records together so future visits can distinguish routine maintenance from a recurring drainage problem.