01
Open a sufficient working width
Remove enough slate on both sides to expose the complete valley and sound substrate. Number reusable pieces and protect them from foot traffic and mixing.
02
Correct the underlying geometry
Repair deck damage, verify slope and install the specified underlayment and metal with suitable width, laps and movement provisions. Do not repeat an undersized or trapped detail.
03
Rebuild stable valley cuts
Cut replacement slate so corners remain strong and the drainage channel stays open. Maintain course lines and use matching thickness to prevent rocking.