Can Chimney Flashing Be Repaired?

The Question Behind the Question

People asking this usually want to know whether they are being sold a bigger job than they need. Fair enough, so here is the honest split.

A flashing that has lifted, slipped or come out of its chase is usually a repair. Nothing has failed as a material; a fixing has let go and the lead needs re-dressing, re-wedging and repointing.

A flashing that has split can be repaired, but only after establishing why it split, because the reason usually predicts what happens next.

A flashing that has failed because somebody used a cement fillet instead of lead is not a repair at all. There is nothing there to repair.

Lead Welding Is a Real Thing

Lead can be joined and repaired by lead welding - traditionally called lead burning - where the parent metal is fused with a lead filler rod using an oxy-gas torch. It is a proper structural repair rather than a filler, and the joint is lead all the way through.

It is worth doing on a large or valuable sheet, on historic work, and where a split is local and the rest of the piece is sound and correctly sized.

It needs somebody with the equipment and the skill, and it needs to be done off the roof or with proper hot-work precautions, which on a chimney means access and time. On a small, ordinary house flashing that split because the piece was too long, replacing it correctly is usually the better value.

What it is not is a bodge, and if somebody proposes it on a good sheet, that is a sign they know what they are doing rather than the reverse.

When a Patch Is Legitimate

When the failure is local and the cause is external - something struck it, a wedge came out, a section was disturbed by other work.

When the rest of that piece is correctly sized, correctly lapped and in good condition.

When the other three pieces of lead around the stack are of a different, newer age so you are not simply queueing up the next visit.

And when the building is one where retaining original fabric matters.

When It Is Not

When the piece split because it was too long. Lead expands and contracts a great deal, and guidance puts sensible maximum lengths for cover flashings at around a metre and a half with lapped joints between pieces. A single continuous run down a stack fatigues along a fold, and repairing that fold puts you back where you started with a piece that still cannot move.

When all four pieces are the same age. Getting safe access to a chimney is a large part of the cost and it is the same whether you renew one piece or all of them.

When the underlying problem is the masonry rather than the lead. New or repaired lead on a stack that is soaking through eroded pointing changes nothing, and on the Dee estuary that is a common finding - salt-laden wind erodes mortar joints on the weather face considerably faster than inland.

What Is Never a Repair

Sealant over a split. Bituminous paint over a split. Self-adhesive flashing tape over a split. All three shed water for a season, then shrink, crack or lift at the edges and hold water against the defect rather than letting it drain.

They also have to be removed before anything proper can be done, so the eventual correct repair costs more than it would have.

There is one exception, and it is genuinely legitimate: a temporary make-safe in bad weather, described to you as a make-safe, with the permanent repair arranged. Stopping water entering tonight is worth doing. Being told that is the repair is not.

One Flint-Specific Point

Lead has scrap value and stolen leadwork is a real problem, particularly on buildings that are empty, out of sight or set back from a road.

If lead has disappeared from your chimney rather than failed, that is worth knowing when you report it and when you claim, and it changes what a sensible replacement looks like - terne-coated stainless steel or a proprietary lead alternative is sometimes the right answer on a property that has been targeted before.

On an ordinary occupied house, lead remains the right material and the risk is low.