Possible causes
- High winds lifting loose or poorly fixed tiles
- Corroded nails ('nail sickness') on older slate roofs
- Frost damage to porous or ageing tiles
- Foot traffic from aerial or satellite installers
Warning signs
- Tiles or pieces of slate in the garden or gutter
- Visible gaps or misaligned rows on the roof
- Daylight showing in the loft
Typical solutions
- Replacing individual tiles or slates with a matching type
- Refixing slipped slates with clips
- Re-roofing where many slates are slipping due to nail sickness
When to call a roofer
Soon after you notice it. A single gap lets rain onto the underlay and battens, and neighbouring tiles can loosen in the next storm.
This is general guidance. The cause of any roof problem can only be confirmed by inspecting the roof.