01
Survey the existing roof first
Record the original roof's dimensions, visible coursing, thickness, color range, and important details. Ask the designer and slater to review where old and new roof planes meet. The junction may influence the layout and drainage more than a sample match alone. Establish whether the existing roof is suitable to retain around the proposed work.
02
Choose continuity deliberately
The project may aim for a close match or an intentionally distinct but compatible roof. Either choice should be explicit. Review the transition through drawings and material samples, and clarify who owns the connection between new construction and retained roofing. Keep a record of both materials so future repairs do not treat the addition as though it were identical to the original building.