01
Define the work clearly
A proposal should distinguish replacing damaged slates from repairing flashing or masonry. Ask which roof slopes are included and whether the work covers only marked defects or a wider inspection. Replacement pieces should be described well enough to compare size, thickness, and appearance. A vague promise to patch the roof leaves too much uncertainty about the finished repair.
02
Decide how surprises will be handled
Hidden conditions may become visible only when pieces are removed. Agree on a notification process before extra work proceeds, with photographs and an explanation of the proposed change. Ask for completion pictures and a short record of materials used. Keep the contractor's contact details with the repair record so a later inspector can understand what changed and where to look first.