Lead flashings and lead-lined valleys and gutters are common on older houses across London and the South East. Lead is a good material. It’s easy to shape, it lasts a long time when it’s fitted properly, and it copes with the movement between a roof and a wall.
When it does fail, though, the water it was keeping out tends to travel. This guide explains why lead fails, what theft looks like and how flashing faults show up inside the house.
Where lead is used on a roof
- Flashings: where a roof meets a wall, a chimney or a party-wall upstand. The top edge is tucked into a mortar joint.
- Soakers: small pieces of lead under each slate or tile along an abutment, working with the flashing above.
- Valleys: where two slopes meet in an internal corner.
- Gutters: parapet gutters, box gutters and the central valley of a butterfly roof.
- Dormers and bays: cheeks, small roofs and bay window tops.
Why lead fails
Lead moves as it warms and cools. If it was laid in pieces that are too long, or fixed too tightly, it can crack as it moves. Other common causes are:
- the mortar holding the top edge in the wall weathering away, so the flashing lifts or drops out
- wind lifting a flashing that wasn’t properly secured
- lead that was too thin for the job
- old patches of bitumen or sealant that have broken down and trap water
- valleys and gutters blocked by debris so water sits on the joints.
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Lead theft
Lead is a target for theft, particularly on houses with easy access from flat roofs, scaffolding or neighbouring buildings. Signs include bare strips along walls or chimneys where lead used to be, missing sections in valleys, and sudden leaks after a period of dry weather. Some owners replace stolen lead with other materials. A survey notes what’s there now and whether it looks complete.
If you think lead has been taken, report it to the police and tell your insurer. Temporary cover may be needed quickly, because a missing flashing can let a lot of water in during the next spell of rain.
How flashing faults show inside
A failed flashing doesn’t always leak directly below. Water can run behind the flashing and down the inside of a wall, or along a rafter, before it shows. Typical signs are:
- damp on a chimney breast in the loft or a top-floor room
- staining where a ceiling meets a party wall or gable
- damp below a dormer or around a bay window
- wet timbers along one side of the roof space.
Our guide to finding a roof leak explains why the stain is rarely under the hole.
What a survey looks at
A roof survey checks the flashings, soakers where they can be seen, valleys and gutters, and records lifted, cracked, patched or missing lead. If you have an active leak, a roof leak investigation focuses on tracing the route the water is taking. Moisture detection, and thermal imaging where useful, can help narrow it down. We inspect what can be seen safely, from the ground, windows, loft and, where applicable, by drone.
Quick answers
Can sealant fix a cracked lead flashing?
It may slow a leak for a short time, but it often breaks down and can trap water. A survey report notes where patches have been used and how they look.
How can I tell if lead has been stolen?
Look for clean lines of mortar or bare brick where lead used to sit, especially around chimneys and along walls. A sudden leak after dry weather is another sign.
Do flashings on newer roofs use lead?
Many still do. Some newer roofs use other flashing materials. A survey describes what is fitted and its condition.
Related services
More advice
- Chimney Stack Defects: Flaunching, Pots, Leans
- Butterfly Roofs and Valley Gutters Explained
- Why Roof Leaks Are So Hard to Find
- Victorian Terrace Roofs in London: Common Defects
- All advice
This guide is general information about roofs and roof surveys. It isn’t legal, insurance or structural engineering advice; for those, speak to a suitably qualified professional.