Slipped and Cracked Roof Tiles

Slipped and cracked tiles are among the most common defects on clay and concrete tile roofs worldwide. A slipped tile has moved down out of its course, usually because its nail, clip or nib has failed. A cracked tile has fractured but may stay in place. Both can let wind-driven rain reach the underlay and battens, and a gap can let further tiles move.

Causes

• Failed fixings: corroded nails, missing clips, or nibs broken off the back of the tile.
• Rotting or broken battens that no longer hold the tile.
• Foot traffic: walking on tiles, especially unsupported parts of profiled tiles, is a frequent cause of cracks. Satellite, aerial and solar installers and other trades can damage roofs if they do not use roof ladders or boards.
• Impact from hail, falling branches or debris.
• Frost damage in porous tiles, causing spalling and lamination.
• Wind uplift, especially at verges, ridges and eaves where tiles are not mechanically fixed.
• Building or roof movement and thermal stress.

Spotting the problem

Tiles that sit out of line, gaps that show underlay or battens, debris in gutters, and damp patches in the loft after rain. Binoculars or a drone allow a safe check from the ground.

Repairs

Typical repairs include sliding a single tile back and refixing it, replacing broken tiles with matching ones (lifting the tiles above with wedges and using a slate ripper to cut old nails where necessary), and fitting tile clips or hooks. Minor hairline cracks are sometimes sealed as a temporary measure, but manufacturers generally recommend replacing cracked tiles. Matching older or discontinued tiles may require reclaimed stock.

Prevention

Minimise foot traffic, insist that other trades use roof ladders or crawl boards, and ensure tiles are fixed to current standards when reroofing. In the UK, BS 5534 sets fixing requirements for slating and tiling; other countries have their own codes and manufacturer installation guides, and in hurricane-prone regions tile fixing is tightly specified.