The short answer
By working with the roof that is there. Old timbers have moved, coverings have been patched, and the aim is to cure the fault with matching materials rather than strip more than necessary. A survey with photographs shows the true state of the slope and decides how much work is needed.
A village with a Norman church, a Hospitallers' gateway and Domesday mills has roofs that have outlived several owners and several rounds of repairs. The sensible approach on all of them is patient and specific, and it starts from the building, not from a product list.
Q1.1Why find the cause first?
Water often shows itself far from where it enters, running along a rafter or a felt lap before it drips. A stain in a bedroom may start at a slipped tile, a cracked valley, a failed chimney flashing or a gutter that has been overflowing against the wall. We trace the route before we propose anything, because treating the stain instead of the cause is the commonest way for a repair to fail within a season or two.
Q1.2How is the existing covering matched?
Tiles and slates are replaced to match the size, colour and texture of the existing covering. Where a roof is stone slate, the courses shrink in size from eaves to ridge, so replacement stones must be chosen to fit that pattern. Our Cotswold stone roofing page explains how those roofs are laid and why reclaimed stone is handled with care.
Q1.3Why do the fixings matter as much as the covering?
On many old roofs the covering outlasts whatever holds it up. Rusted nails, rotted pegs and softened battens let sound tiles slip. Replacing those, instead of the whole covering, is often the better answer and the cheaper one. It also keeps the weathered look of the roof, which matters in a village where so much is old. Pegs, nails and battens are cheap parts of a roof, but they decide how long the expensive parts stay up.
Each visit ends with photographs of your roof and a written quote, so the decision rests on evidence you can look at yourself at the kitchen table.