Roof tile repair across all 33 London boroughs

Failed lead flashing is the most common cause of chimney and valley leaks in London properties. Lead deteriorates gradually — it cracks along the fold lines, pulls away from the mortar chase, or simply thins with age until it no longer forms a watertight seal. On Victorian and Georgian properties, the original cast lead is often over 100 years old and has reached the end of its serviceable life.

There are several distinct types of lead flashing on a London roof:

• Step flashings — individual lead soakers interlocked with tiles at abutment walls, stepping up the slope of the roof.
• Soaker tiles — hidden lead pieces that sit beneath each tile course directly behind a chimney stack.
• Back gutter — a lead-lined horizontal gutter at the upslope face of a chimney, directing water around the stack.
• Parapet gutters — found on Georgian and Regency properties; original cast lead, often degraded, sometimes concealed under a stone coping.
• Valley lead — pressed or rolled lead lining the internal valley where two roof slopes meet.

London's climate — mild, damp winters with limited direct sunlight on north-facing slopes — is ideal for moss and lichen growth. While moss may appear harmless, it acts as a sponge retaining water against tile and mortar surfaces, accelerating freeze-thaw erosion of pointing and degrading the surface of concrete tiles over time. Thick moss growth also lifts tile edges, allowing wind-driven rain beneath the tile course.

Our moss treatment process begins with a biocidal wash applied to the entire roof surface. The biocide kills moss, algae, and lichen at the root. The dead growth is then soft-washed from the surface — we do not use high-pressure washing, which can damage tile surfaces and dislodge mortar. Finally, zinc or copper strips are fixed at the ridge: as rainwater washes over the metal strip, ions are released that prevent moss regrowth for 10–15 years.

Ridge tiles sit at the highest point of a pitched roof, bedded and pointed in mortar. They are exposed to the harshest weather conditions — wind, rain, and freeze-thaw cycles — on any part of the roof. On a London house, ridge mortar typically lasts 15–25 years before it begins to crack, erode, and eventually fail.

A failing ridge is one of the most common causes of a leak that is difficult to trace from inside the property. Water enters not through the ridge tile itself, but through the open joints between tiles once the mortar is gone. It then runs along the ridge board or down the inside of the tile course before appearing as a stain on the ceiling — often metres away from the actual point of entry.

Ridge re-bedding involves carefully lifting each ridge tile, removing all old mortar from the tile and from the underlying tile course, and re-bedding the ridge tile in a fresh mortar mix appropriate to the tile type. All bed and perpendicular joints are then pointed to a neat, weathertight finish. On older properties, we use a lime-based mortar rather than Portland cement — Portland cement is too rigid and causes cracking and spalling in the softer brickwork and tile surrounds common on Victorian and Edwardian roofs.