Individual tile replacement
Replacing one or two broken tiles is a straightforward job on any sound roof, carefully lift adjacent tiles, remove the broken tile, slide the replacement into place, and re-nail or clip where required. The trap is matching: modern replacements of a 40-year-old concrete tile rarely match visually, and on a period roof the wrong replacement stands out badly. We source matching where it matters. Where an exact match cannot be sourced (discontinued profiles), we recommend salvaged tiles from a reputable reclamation source, or advise a wider re-cover if aesthetics matter.
Batten replacement
Roofing battens are typically 25×50mm or 25×38mm treated softwood, fixed horizontally across the rafters at the correct gauge for the tile profile. Battens go soft when the underlay above them has failed and they've been repeatedly wetted, you can normally identify a rotten batten by pushing a screwdriver into it. A rotten batten cannot hold a nail, and any tile fixed to it is effectively loose. Localised sections of rotten batten can be replaced within a wider re-cover; if rot is widespread, the correct answer is to strip and re-batten the whole affected slope.
Underlay membrane replacement
The underlay membrane is the second line of defence against water, designed to shed any water that gets past the tile layer down and out at the eaves. Original 1960s–1970s bitumen felt underlay had an expected service life of 30–40 years; most has now reached or passed that. Modern breathable underlays (Type LR to BS 5250) are much longer-lived, don't trap condensation, and eliminate the need for separate loft ventilation in many cases. Replacing the underlay requires stripping the tiles above it, so it is normally done either as a full-slope re-cover or as part of a full re-roof rather than as a standalone job.
Nail sickness
'Nail sick' is the roofing term for a roof where the original ferrous fixing nails have corroded through, so tiles or slates that appear intact are actually being held in place only by gravity and friction. In wind, they lift and slide. Nail sickness is common in slate roofs over 80 years old with original iron nails. The fix is to strip the affected slope, re-nail with modern copper or stainless steel fixings, and, while access is there, usually to renew the underlay membrane at the same time.
When targeted repair vs full re-cover is right
For a sound roof with a few broken tiles: targeted replacement is correct. For a roof with rotten battens or failed underlay in one localised area: section repair is correct. For a roof where the underlay is at end of life across the whole surface, or nail sickness is widespread, or multiple slopes are affected: a full re-cover or re-roof is more economical than repeatedly returning for individual repairs. We tell you honestly which category your roof is in after inspection.
