Once tiles have passed their life expectancy it is uneconomical to keep repairing them, it is time for a complete new roof.
This is a similar process.
The Slates go directly on to sarking board using copper nails in compliance with BS55342014. Also there is a big market variation in Slate to suit your individual needs. Whether that be reclaimed Scotch Slates or brand new Welsh slates or anything in between. We always use quality material and install to BS342014 specification for both Tiled and Slate roofs.