Most roof leaks do not start in the middle of a slope. They start where the slope stops: against a gable wall, round a chimney stack, or at the side of a dormer. These are abutments, and at each the two structures meeting will expand, settle and weather at different rates. Lead is the traditional answer because it can be folded, dressed and fixed into almost any shape, and when it is built properly an abutment can stay dry for a very long time. When it is built badly it leaks within a few winters, however good the metal. This guide explains the parts of a lead abutment, namely the soaker, the step flashing and the cover flashing, and the order in which they go on. It looks at how the lead is held to the wall, where chimney leadwork differs, what typical UK costs look like, and the signs that a flashing is on its way out. The aim is to help you follow what a roofer is doing and to ask the right questions.
What happens where a roof meets a wall
A pitched roof is made of many small units, each one lapped over the one below. Rain runs off the slates or tiles and drops into the gutter. At a wall, that system stops working. The wall is a vertical face, rainwater runs down it and arrives at the junction in a sheet, and the gap between roof and wall, however narrow, is a direct way into the building.
The solution has two layers, and both are needed. The first layer is made of soakers, which are small pieces of lead folded to an angle and placed one under each slate or tile along the roof edge. Half of each soaker lies flat beneath the covering and the other half turns up the wall. The slates sit on top of the flat part and shed water onto it, and the soaker carries that water down to the next course and eventually onto the roof below.
The second layer is the flashing, a strip of lead that covers the upturned edge of the soakers and the junction with the wall. Its top edge goes into a joint or chase cut in the masonry above, and the lead is dressed down over the soakers, so that rain running down the wall is turned outward onto the roof and cannot slip behind the lead. In a stepped version, where the wall meets a sloping roof, the flashing is cut in a staircase pattern so that each step follows a course of brickwork or stone.
Neither layer works alone. Soakers without a cover flashing leave the top edge open to wind-driven rain, and a flashing without soakers leaves the lap beneath it dependent on the roof covering. When we are called to a damp patch beside a chimney or gable wall, one of the first questions is whether both layers are still there.
Step flashings, cover flashings and the other shapes
The words get used loosely, so it helps to be precise about the main types you will meet on a house.
Step flashing
A step flashing is the lead that follows a sloping edge up a wall, cut so that it steps with the courses. It is used wherever a sloping roof runs against a vertical face, for example along a gable wall or against the side of a dormer. Each step is tucked into the mortar joint and the lower part dressed down over the soakers.
Cover flashing
A cover flashing runs on the level, across the top of an upstand such as a parapet, a flat roof edge or the foot of a chimney. It covers the top of a lead or felt upturn so that water running down the wall falls clear. Cover flashings are fixed into a chase or a joint in the wall and held there by wedges.
Apron and back gutter
At a chimney, the front face gets an apron, one wide sheet of lead that rests on the roof ahead of the stack and climbs its front face. The back, where the roof slopes down into the chimney, needs a back gutter that channels water round the stack to either side. The sides get stepped flashings, which are lapped with the apron and back gutter at the corners.
Soakers on the slope
Soakers are not flashings, though they are often described together. They go in as the roof is covered and are hidden once the course above is laid. This is one reason replacing a flashing without lifting the covering beside it only does half the job. If the soakers are missing, split or too short, the flashing alone cannot hold the line.
Our wider page on lead bay roofs shows how the same shapes are used on a small period roof.
How a flashing is held in the wall
Lead does not stick to masonry and should not be asked to. It has to be held in place mechanically, and the way it is held decides whether the flashing lifts in a gale or stays down through many winters.
The traditional method is to cut a groove, called a chase, along the line of the flashing, or to use an open mortar joint, and tuck the top edge of the lead into it. The lead is then secured by lead wedges tapped in at intervals. The Lead Sheet Association gives a maximum distance of about 500 mm between wedges for a cover flashing. The joint is then pointed with mortar, and on an older building the mortar should be a lime mix. On a chimney at 7 Walcot Buildings, the Bath Preservation Trust urged lime for the flaunching and repointing and noted that cement may have worsened damage to the stone.
The length of each piece is limited too. One lead manufacturer sets 1,500 mm as the longest piece in codes 4 and 5 for these flashings. In practice that means a long abutment is laid in several overlapping lengths, each one lapped over the next, so that the lead can move with the temperature and not rip itself along the fixing line. A single very long strip looks tidy at first and ripples within a few seasons.
The code of lead matters here as well. Code 3 is listed for soakers only. Code 4 suits both soakers and flashings, and code 5 is the more general choice above the roof line. Our guide to lead codes sets out the thickness and weight of each.
The lower edge of a cover flashing is left free so it can move, and a good fitter dresses it tight but never glues it down. A sealant bead along the bottom edge of a flashing can look like a repair and can trap water behind the lead. It is a symptom of a joint that needed proper attention.
Chimneys: the hardest flashing on the roof
A chimney stack sits in the middle of the roof and sheds water on four sides. It has to be flashed on all four, which makes it the most difficult abutment on most houses and the one that leaks most often. MyBuilder's chimney repair cost guide (2026) gives a typical range of £250 to £1,200 for a flashing repair in the UK. It is a mid-range repair because the work involves getting to the stack safely as well as dressing the metal.
The lead round a chimney typically comprises an apron at the front, a back gutter behind, and stepped flashings along the sides, all tucked into the stack. Where the old lead has failed, the usual causes are cracked or missing pointing round the chase, lead that has split along a fold, or cement fillets that were used in place of lead and have cracked. A cement fillet is a sloping band of mortar between the roof and the stack. It may look sound from the ground, but it cracks once roof and stack drift apart, and water gets in behind it.
The top of the stack is a separate matter. The flaunching is the mortar dressed round the base of the pots, sloped so rain runs off. If it is cracked, water goes down the flue and into the house. A roofer looking at chimney leadwork should look at the flaunching, the pointing and the pots at the same visit.
On costs, MyJobQuote's chimney leadwork guide (22 September 2026) gives a typical patch repair at £150 to £250 and a full replacement at about £570 on average, which falls to £350 to £460 without scaffold and rises to £700 to £920 with it. Those are typical UK ranges and not our prices. After the survey, the quote in writing states what is renewed, what stays and how the stack is reached.
Signs a flashing is failing
Many flashing faults are visible from the ground if you know where to look, and others only appear from the loft. Here are the signs that justify a closer look.
- Damp or a brown stain on the ceiling or the wall beside a chimney or gable. This is the commonest sign of water getting in at an abutment.
- Lead that has lifted or dropped away from the wall, leaving a gap you can see light or sky through.
- Splits and holes in the lead, especially along fold lines and at corners.
- Stained or crumbling pointing above the line of the flashing, where the chase has opened.
- A bead of sealant or a strip of tape along the junction. Someone has already tried to fix it, and the underlying fault is still there.
- Slipped slates or tiles at the verge side, which suggests the soakers beneath have moved.
Lead flashings are meant to last. MyJobQuote's leadwork guide (2026) gives a correctly installed flashing as lasting over 80 years, and over 100 for higher codes, as a typical figure that depends on exposure and workmanship. When a flashing fails much sooner, it points to installation: wedges missing, lengths too long, soakers absent, or pointing in the wrong mortar. The longer view is on our page about lead lifespan.
One more thing to check is what has been used in place of lead. Self-adhesive flashing tapes, bitumen-backed strips and mortar fillets are all sold as quick repairs. They can hold for a while, but they are not equal to lead, and on a period roof they stand out. If your roof has a mix of repairs, a survey can tell you which are sound and which will need replacing together.
Repair, renew and what to expect on a period house
Whether a flashing can be repaired or must be renewed depends on how much of it is still sound. A single split in a long piece can sometimes be patched, but a patch on a flashing that has lifted for its whole length is a short-term fix. If the lead is thin, creased and cracked at many points, or the pointing has gone along the whole abutment, renewing the flashing is the better course. Where a repair will hold, we repair; where it will not, you hear it from us before any lead is cut.
The best time to renew an abutment is when the roof beside it is being worked on, since the soakers can be inspected and replaced at the same time. If a slate or tile course is lifted anyway, the extra cost of proper soakers is small compared with returning later with scaffolding.
On a house in Bath, the building often shapes the work. Where a period house has a stone parapet or a tall stack, the flashings often run into lime-mortared stone rather than brick. That means working with the stone, choosing lime mortar for the pointing, and matching the existing lead where it is sound. On a listed house, altering the lead can need consent from B&NES Council, so raise it with them before anyone starts. Our larger guide to a box gutter relining shows how these details are costed on a bigger scale, and our page on lead flat roofs covers the sheet work that often joins up with a flashing.
The survey comes first. We go up, look at the soakers and wedges, check the pointing and photograph your own roof. The fixed price follows in writing, naming the code and the length of lead, and it is worth asking whether the stepped flashing will be chased into the mortar joints rather than the brick face. Read more about the trade in our lead roofing service.