Distinguish a broken slate from a wider problem
Ask the roofer whether the affected slate is cracked, displaced or associated with deteriorated fixings. Repeated slipping deserves an explanation of the wider roof condition. If more extensive work is recommended, request photographs and a clear account of why a smaller repair would be insufficient.
Specify a suitable replacement
Colour is only one part of matching a slate. Ask how the proposed material compares in size, thickness and profile, and how it will fit the existing arrangement. Where reclaimed slates are suggested, ask how their condition will be assessed. The quotation should identify the intended material rather than simply saying ‘replacement slate’.
Include the adjoining roof details
A slate repair beside a chimney or wall should consider the adjoining flashing as well as the slate itself. Ask whether those junctions have been assessed and whether any related work is included. This makes it easier to understand which defects the quoted repair is intended to resolve.
Check the approach for an older property
Before agreeing changes to an older roof, establish the existing materials and any known heritage designation. Lancaster City Council provides conservation information and a way to check conservation-area boundaries. Take property-specific questions about materials, repair methods and permissions to the council; do not assume the same approach applies to every house. See the council’s conservation guidance.