The short answer
Usually the weakest joints rather than the whole covering: lead around chimneys, the cement at verges, the pegs or nails holding stone and slate, and gutters left clogged season after season. Finding the one that is letting water in is the real work, and often a modest repair is enough.
People expect an old roof to wear out evenly, but they fail at specific points. The covering may be perfectly good across most of a slope while one joint admits water for years.
Q3.1Why do verges and gables crumble?
At a gable end the covering finishes against the wall, and a cement fillet or a row of bedded tiles keeps it in place. Rain and frost break that bond over time. Once it opens, wind drives water behind the verge and into the wall head. Re-bedding and refixing is a small job if caught early, and a much larger one when the timber behind has rotted.
Q3.2How can I tell if the nails or pegs have failed?
Slipped slates or stones lying lower than their neighbours are the clue, as are gaps of daylight seen from the loft on a bright day. On slate the nail rusts through, and on stone slate the peg decays. In both cases the surrounding stones are usually sound, so we refix them rather than renew them, and we use new fixings suited to the material. Stainless or copper nails are the usual choice for slate, and oak or a modern equivalent for stone.
Q3.3Do gutters really matter on a stone cottage?
They matter a great deal. When a clogged gutter spills over, the wall below stays wet, and soaked stone then draws damp inwards. Our roof repairs page explains how a gutter and a roof are examined together. Where a defect is small we fix only the defect, and the work carries our 10-year workmanship guarantee, in writing.
Photographs from the survey show each fault, so you can see why a given repair is proposed before you agree to it. If you would rather talk it through first, ring 01793 626096 or send a message on WhatsApp, and the enquiry form is on every page.