Lead Flashing Coming Away From the Wall

A flashing against a wall does not stick to it. Its top edge is turned into a groove cut in the brickwork, the chase, and wedged with small lead folds every few hundred millimetres. The chase is then filled with mortar or a flexible sealant, which keeps the wedges still and rain out. The sheet itself hangs down over the roof covering and is held at the bottom by its weight and clips.

Every part of that holding system can fail. Mortar shrinks and crumbles after years of frost. Sealant dries, cracks and pulls away from the brick. Wedges fall out when the mortar goes. The chase may also have been cut too shallow in the first place, or on a soft brick that has since weathered back. Once the edge is loose, wind pulls the lead away from the wall and it starts to flap and tear.

You usually see it from outside first, as a lifting edge or a gap with daylight behind, long before a stain shows indoors. A strip hanging clear of the brickwork has already stopped doing its job, and each shower tests the gap.

Before anything is fixed, the cause has to be found. A roofer looks at the chase to see how much mortar remains and whether the brick behind has crumbled, at the wedges to see whether they are present and tight, and at the lead along its length for cracks, folds that have opened, thin patches and holes from old nails. They will also check whether the wall itself is moving, since a flashing cannot hold to a wall that is cracking.

Photos of each of these are part of our survey, so you can see the chase and the strip yourself. We also check the roof covering below the flashing, since tiles that have slipped let water in at the same spot and are often mistaken for a flashing fault.

It is worth asking whether the sheet is long enough. A flashing cut short has no spare length to be re-dressed, and a patch of a different age beside old lead often fails at the join. The aim is to decide between repair and replacement on evidence, not on guesswork.

Where the lead is sound, the repair is straightforward. The old mortar or sealant is raked out of the chase, the dust is cleared, and the lead is pushed back into the groove and wedged with fresh lead wedges at close intervals. The chase is then repointed with mortar, or a flexible sealant where the brickwork calls for it. The lower edge is checked for clips so wind cannot lift it again.

The order matters. Pointing a chase before the lead is properly wedged just hides a loose strip behind new mortar, and the flashing will lift again at the first gale. Leaving the mortar to cure also matters, and so does a dry day, because fresh pointing washed out by rain has to be done twice. Ask the roofer when the weather window suits.

If the brick has broken away, the chase may need a short run cut afresh in good brick above it. Where the lead is cracked, thin or has holes, we would sooner fit a new strip than patch an old one. Our pages on repointing lead flashing and how lead flashing is fixed go through the detail.

As a national guide, In Checkatrade's June 2026 table, mending lead flashing runs from £50 to £70 per metre and Code 5 stepped flashing from £80 to £120. A second guide, MyJobQuote, updated on 22 September 2026, puts a full chimney leadwork replacement at £350 to £460 without scaffold and £700 to £920 with it. Those are yardsticks. What you pay turns on the run of wall, how sound the brick is and the working height.

Access is the swing factor. A single-storey flashing can often be reached from a ladder. A gable wall or chimney two floors up needs a tower or scaffold, and that can cost as much as the lead work. Check that the total states whether VAT and scaffold are included, and what has been assumed about the chase.

Our survey leads to one total, written down, with the photos behind it. Lead is long-lived, with one national cost guide saying lead flashing can last for over 80 years, so a failing strip is usually a fault in how it is held rather than the metal. See whether lead flashing can be repaired or visit our lead work page.