A flashing is lead folded over the meeting line of a roof covering and anything solid beside it: a chimney stack, a gable end, a dormer cheek, a wall shared by terraced houses. Roof timbers and masonry settle and warm at different speeds, so the line between them cannot be filled solid. Lead is draped across it instead, because it flexes without breaking.
Three shapes do most of the work: stepped flashings up a sloping wall, cover flashings along a horizontal line, and aprons at the foot of a stack. Each fails in its own way and is mended in its own way. This guide takes each in turn and says where a repair will do and where the lead should be renewed. The top edge, where the lead is sealed to the masonry, has its own answer on pointing lead flashing. For the whole service, start at lead roofing.
Three flashings, three jobs
It helps to know the names, because they tell you what has gone wrong and what a roofer means when a quote lists one of them.
Stepped flashing
Where a roof slope runs up against a wall that rises above it, such as a gable end or the side of a chimney, the lead steps up the wall in line with the slope. Each step is turned into a slot cut along a mortar joint (the chase) and fixed there. Underneath the stepped lead sit small folded pieces called soakers, one for each course of tile or slate, which carry the water out over the covering.
Cover flashing
A cover flashing is a flat strip that hangs down over a joint to shed water across it. You find it along the head of a lean-to roof where it meets the house wall, over a back gutter, or at the junction of a porch roof and the wall behind.
Apron flashing
An apron is the piece laid at the downhill face of a chimney stack, the side that faces the eaves. It sits over the tiles or slates below and rises up the brickwork or stone above. The uphill face of a stack gets a back gutter, a small channel that moves water round the stack.
| Flashing | Where it sits | Usual weak point |
|---|---|---|
| Stepped | Up a sloping wall or stack side | The chase and the mortar around the steps |
| Cover | Horizontal joint below a wall or beneath a window sill | A lifted edge that lets wind-blown rain behind |
| Apron | Downhill face of a chimney stack | The turn at the corners and the lower edge over the covering |
How lead flashings fail
A handful of causes account for nearly every leak we trace to a wall or stack, and we work through them in this order on site.
Pulled out of the chase
The top edge of the lead sits in a groove in the wall. If the mortar behind it perishes, the lead can drop out and hang loose, which lets rain run behind it. Old stone and soft lime mortar crumble at the edge of a chase, and the lead follows.
Lifted by wind
A cover flashing with no clips along its bottom edge can be lifted by gusts, then flapped about until it creases, work-hardens and tears. Wind is a quiet cause: it loosens a flashing for years before the first stain appears.
Cracked from movement
Lead expands and contracts with temperature. A piece cut too long, or held too firmly, tears along a fold. MyJobQuote refers to fitting the correct code in 1.5 metre lengths for this reason, and our answer on lead sheet lengths explains the thinking.
Wrong code, wrong repair
According to Leadworx, Code 4 has become the usual pick for general flashing, and Code 3 suits soakers. A flashing in a thinner sheet than the job needs wears sooner. A past repair made with bitumen tape, mastic or a smear of sealant can hide the real fault for a season and leave rot behind it.
Theft and damage
Lead is valuable scrap, and flashings at the back of a house are an easy target. Our guide to lead theft from roofs covers prevention and what to do when it happens.
Reading the signs: from the ceiling to the stack
Flashing faults show up as damp in predictable places, and knowing the pattern helps when you describe the problem to a roofer.
- A brown mark on a chimney breast, or on the ceiling next to it, often means water is entering round the stack.
- A line of damp down a party wall, in the loft or in a first-floor room, can come from a stepped flashing that has pulled away.
- Damp at the head of an extension, along the wall where it joins the house, points to a cover flashing or an abutment fault.
- Dark drips on the stack itself after rain, with efflorescence (white salts) on the brick, show that water is tracking into the masonry.
What can be seen safely
From a window or the garden, with binoculars, you can check that the lead is still tight to the wall, that no strip hangs loose, and that the mortar line above it is intact. Look for bright, clean metal where lead has recently moved, and for white streaks below it. You should not need to climb to find out whether something looks wrong.
Checks before any lead is touched
Before we price, we look at what the lead is fixed to. Mortar that rakes out as dust, bricks that have spalled at the chase, or a stack with open joints will not hold new flashing for long. We also check that the roof covering beside the flashing is sound, because a slipped tile at a wall junction can leak while the lead is blamed for it.
What we record
At a survey we photograph each flashing close up: the top edge, the corners, the junctions between the steps and the condition of the soakers where they can be seen. You receive the pictures of your own roof, so the advice rests on evidence you can see. We also check the chimney or wall itself, since a flashing cannot hold on crumbling masonry. Should the stack lean, or the brickwork lie open, the work begins there, and our chimney repairs page covers it.
Repairing each flashing
How much work is needed depends on the extent of the damage. These are the options, lightest first.
Re-fixing and re-pointing
If the lead itself is sound but the top edge has dropped, we can re-seat it. That means raking out the failed mortar, tucking the lead back into the chase, securing it with lead wedges or clips, and sealing the joint. Whether the closing material is mortar or a flexible sealant depends on the wall, and our pointing answer sets out the choice.
Patching a small fault
A short crack or a puncture can be cut out and a patch lapped in beneath the old metal, then dressed flat. This works when the surrounding lead is healthy. If the strip is thin and cracked in several places, a patch moves the problem to the next fold.
Replacing a run of stepped flashing
Where individual steps have failed, a section can be stripped and replaced, with new soakers if the old ones are poor. This is often the case on a gable that has lost its steps to years of frost and wind.
Renewing a whole apron or cover flashing
A flashing that is split along its length, or made in a thin code, is better replaced in full. We cut the new lead in the right code and in short lengths, form the turns at each corner, secure the top edge and clip the bottom.
A bead of sealant along the top of an old flashing slows a leak for a while. It does not mend lead that has torn.
Prices from published sources
Published national guides show the scale of flashing work. They are not Supreme Roofing prices, and your own figures arrive in the written quote after the survey.
| Job | Typical range | Source |
|---|---|---|
| Chimney flashing patch | £150 to £250 | MyJobQuote, 2026 |
| Flashing repair on a chimney | £250 to £1,200 | MyBuilder, 2026 |
| Lead flashing repairs, per metre | £50 to £70 | Checkatrade, 2026, ex VAT |
| Stepped flashing, per metre (Code 5) | £80 to £120 | Checkatrade, 2026, ex VAT |
MyJobQuote's full replacement figures average £570. It gives £350 to £460 without scaffold and £700 to £920 with it. The gap is a reminder that access often costs as much as the lead.
What moves the price
The main drivers are scaffold, the length of flashing, the code, the state of the masonry behind it and how much covering must be lifted alongside. A flashing high on a gable with steep access costs more than one at a low porch. Our lead flashing cost guide goes through the numbers in detail.
Our quote covers scaffold, strip-out, the lead by code, labour, waste and making good, and shows VAT, since roof repairs are normally standard-rated.
Lead, or something else on the flashing
Lead became the traditional metal for flashings because it endures. MyJobQuote puts a correctly installed flashing at over 80 years, and over 100 years in higher codes. If an old flashing has failed early, the cause is usually one of those listed above rather than the material.
Where lead has been stolen more than once, or where a client asks for a different metal, there are alternatives, and they are not all equal. The properties of GRP, synthetic flashing strip and zinc are described in our guide to lead alternatives. On listed buildings the like-for-like rule matters, and a change of material needs the conservation officer's agreement before work starts.
Making the decision
Scale matters too. A short wall flashing over a rear extension is a quick job from a ladder or low scaffold. A long stepped run up a gable, or a stack on a steep ridge, needs access built first, and that is why the same fault can be priced very differently on two houses.
We would rather repair a flashing that is sound than renew it for the sake of it. When the lead is good and the fault is the fixing, a re-fix is the sensible job. When the sheet is thin, torn in several places or held on perished stonework, renewal gives a result that lasts. The survey photographs and the written quote show which one it is, and you can see the reasoning before anything is booked.
Work on a flashing is covered by our 10-year workmanship guarantee, in writing. Offcuts and old lead leave with us when the job ends.