01
Map the work boundary
Ask the window contractor which trim, siding, or flashing must be removed. Have the slater review any connection that meets the roof. Identify how tools and materials will reach the dormer without using unprotected slate as a work platform. Photograph the window and adjacent roof before the project begins.
02
Coordinate the concealed details
Agree who restores each part of the opening and who verifies the interfaces before finishes are replaced. If the dormer dimensions change, the slate layout may need additional review. Keep progress photographs along with the final exterior view. This gives future investigators a better record if water later appears near the dormer and the entry point is not obvious from inside.