How chimney flashing works
A typical detail combines pieces of lead dressed with the roof covering and lead chased into the stack. The arrangement varies with whether the chimney sits at a ridge, slope or party wall.
Common flashing defects
- Lead has lifted, slipped or split
- Mortar securing a chase has failed
- Water is trapped behind an incorrect detail
- Temporary sealants have separated
- Nearby slates or tiles are broken or displaced
Repair or renew?
A small local defect may permit a targeted repair. Widespread fatigue, inadequate laps or incorrect detailing may justify renewal. Leadwork should be detailed to accommodate movement rather than fixed as one rigid sheet.
Look beyond the visible stain
Water can travel along rafters or underlay before appearing indoors. That is why the stack, flashings and adjacent roof covering should be assessed together. See our guide to finding chimney leaks or learn about mortar repointing.
What a flashing quotation should include
A useful quotation identifies which lead elements are being repaired or renewed, how the lead will be secured to the chimney, and whether nearby slates or tiles are included. It should also state the assumed access method. Descriptions such as “seal around chimney” are too vague to compare unless the exact defect and material are recorded.
After the repair
Photographs of the completed apron, side details and back gutter help document concealed roof-level work. Internal plaster may take time to dry after the water route is corrected, so immediate staining does not necessarily prove that new leadwork has failed.
Request a flashing inspection