Possible causes
- Lead pulled out of the mortar joint over time
- Cracking from thermal movement in over-long pieces
- Theft of lead
- Mortar or sealant used instead of proper lead details
Warning signs
- Lead visibly lifted or missing
- Damp where a roof meets a wall or chimney
- Mastic or tape patches that keep failing
Typical solutions
- Re-wedging and repointing loose lead
- Renewing flashings in correctly sized code lead