Leadwork methods
How lead flashing is fitted on a pitched roof
Lead flashing seals the joints where a pitched roof meets a wall, a chimney or a dormer. Fitting it well is a sequence of small, exact steps, and knowing them helps you judge a quote.
A tiled or slated roof sheds rain well on its own slopes. The trouble starts where the slope stops, at a chimney stack, a gable wall, a dormer cheek or a bay roof, because the covering cannot simply run into the masonry. Something has to bridge the joint, stay flexible as the building moves and shed water onto the roof, and lead is a metal that can do that job.
Fitting it is skilled work, and this post is a plain description of how it is done, not a call to climb up and try it. The roof edge, a chimney stack and a wall junction all mean working at height, and a mistake with lead does not show until the next heavy rain. What you gain from reading on is the ability to follow what a roofer is doing and to ask the right questions.
The sections run from the pieces and their names, through the lead codes, the sequence for a step flashing and the cover flashing above it, to lengths, movement and party walls, and finally lifespan and cost.
01Flashings
The pieces: step flashing, cover flashing, soakers and aprons
Lead flashing is not one item but a family of pieces, each made for a particular junction. The names matter, because a quote that says "flashings" can mean several of them.
| Piece | Where it goes | What it does |
|---|---|---|
| Step flashing | Up the slope against a wall or stack side | Follows the pitch in a staircase of steps |
| Cover flashing | Across the top of a joint | Hangs over the covering and sheds water onto it |
| Soaker | Under each course of tiles or slates | Carries water from under the covering to the surface |
| Apron | Across the low face of a chimney | Throws water out over the covering below |
| Back gutter | Behind a chimney on the upslope side | Channels water round the stack |
On a wall that runs up the roof slope, the job is usually a step flashing with soakers. On a stack, the apron, the sides and the back gutter work as a set, so the stack is wrapped from bottom to top. A dormer cheek, where the little wall meets the main slope, calls for the same stepped treatment as a gable wall.
Roofers pick lead for junctions like these since it bends to awkward shapes by hand and then stays put. A piece is formed to its junction, not cut off a roll and nailed down, and that forming is the skill. Our page on what lead soakers are explains the hidden pieces that sit beneath the visible steps.
Before any of this starts, the old flashing comes off, the joint is cleaned and the condition of the covering and the timber behind is checked. There is no point fitting new lead over a rotten batten or a loose tile.
02Leadwork
Which lead code goes where
Lead sheet is sold in codes, each a thickness and a colour band marked on the roll. A heavier code is thicker and stiffer, and the right one depends on the job. Royston Lead's cast-lead brochure gives the thickness of each code and the uses it recommends.
Lead flashing questions
Can lead flashing be fixed with sealant alone?
Sealant on its own is a stopgap, not a fitting method. Lead is held by being tucked into a chase or raggle, wedged and then pointed or sealed, so rain cannot get behind it. A bead of sealant over a lifted edge may hold for a spell, but the fixing underneath is what keeps it there.
| Code | Thickness | Colour | Used for |
|---|---|---|---|
| Code 3 | 1.32 mm | Green | Soakers only |
| Code 4 | 1.80 mm | Blue | Soakers, flashings, pitched valleys, dormers |
| Code 5 | 2.24 mm | Red | Flashings, pitched valleys, parapets, box gutters, dormers |
| Code 6 | 2.65 mm | Black | Flashings, pitched valleys, parapets, box gutters, dormers |
Royston recommends Code 3 for lead soakers only. Codes 4, 5 and 6 are all listed for flashings, with the heavier ones also listed for parapets and box gutters. Codes 7 and 8 appear in the brochure for the heavier gutter and parapet work and not for flashings.
Each detail has its code written into the specification. The roofer chooses by junction, exposure and the width of the piece, so two flashings on one house can differ. A quote that names the code is giving you something to check, and a quote that does not is worth a question.
The colour bands are a handy check on site. A roll marked with the wrong colour for the specified code is a mistake caught before the lead goes on the roof. Our post on lead codes explained goes through why Code 4 and Code 5 go in different places.
03In order
Fitting a step flashing against a wall
A step flashing runs up the roof slope where it meets a wall, such as the side of a chimney stack or a gable end. The sequence follows the order the water travels, working from the bottom of the slope upwards, so that each piece laps over the one below.
- Strip the old flashing, rake out the joint it sat in and check the wall face and the batten line.
- Cut a chase, a shallow slot, into a mortar joint at the right height above the covering. The stepped chase follows the line of the brickwork.
- Lay a soaker under each course of tiles or slates and fold its upstand up the face of the wall.
- Dress the step flashing over the soakers and fold its top edge into the chase.
- Wedge the lead into the chase with small lead wedges, spaced along the length, so it stays tight.
- Point the chase with mortar, or seal it with a suitable sealant, so rain cannot get behind the lead.
Two things make the difference between a lasting job and one that fails. The first is the lap: each step must overlap the one below it so that water runs onto the roof and never behind the metal. The second is the fixing at the top edge. Lead is soft, and if it is only nailed through its face, it will tear or lift in a gale.
The covering is cut and set to suit. Tiles or slates at the wall edge lie over the soakers, and a loose or cracked one is replaced before the lead goes on. A neat result shows steps of even size and no gaps at the wall.
On a roof that has settled, the wall and the slope no longer meet at the angle they were built at. Lead is dressed to the real line, not the drawing, which is one reason it is chosen.
04Key points
Cover flashings, chases and what holds them
A cover flashing is a single strip that hangs down over the top of another detail, such as the upstand of a flat section or the head of a roof light. It is the lead you see running horizontally across a wall above the covering.
The way it is held decides whether it lasts. There are two common fixings, and each has its place.
- A chase: a slot cut into a mortar joint, or into the wall face, so the top edge of the lead tucks in and is wedged.
- A raggle: a groove cut into masonry or formed in a pre-cast section to receive a lead edge, a form found on chimneys and stone details.
In each case the lead is turned into the slot, held with wedges and then sealed. Fixing through the face of the lead alone is avoided, because rain can follow the nail or the screw.
The slot itself is cut cleanly, not hacked, because a ragged chase damages the brickwork around it and gives rain a path. On older walls the mortar can be soft, and the roofer checks that the joint will hold the lead before wedging into it.
The face of the flashing must hang over the covering far enough to shed water onto it. If the lap is too short, wind-blown rain gets under the edge. If it is too loose, the metal lifts. Dressing it down onto the covering, without forcing it, gives a firm and watertight finish.
Our page on why lead cracks, why lead flashing cracks, covers the failures that come from poor fixing and from forming the metal too tightly, both of which are avoidable in the way it is fitted.
Which lead code is used for flashings?
Royston Lead lists Code 4, Code 5 and Code 6 for flashings and recommends Code 3 for soakers only. The code is written into the specification detail by detail, so two flashings on one house can differ. A quote naming the code gives you something concrete to check.
05In brief
Lengths, movement and party walls
Lead expands and contracts with temperature, and a long unbroken strip will creep and eventually crack along a fold. So a run of flashing is made up of shorter lengths, each overlapping the next, and each fixed so that it is free to move.
How long a length can be depends on the code, the detail and the exposure, and the specification gives the figure for the job. We do not quote a rule of thumb here, because the right number depends on those factors and not on a single measure. What matters on site is that the laps are generous, the fixings are in the right places and the joints between lengths are not sealed solid.
- A lap where one length overlaps the next lets the metal move without opening the joint.
- Clips hold the lower edge of a cover flashing without pinning it, so it can slide.
- A step flashing is made from individual pieces, one per course, so the movement is spread along the slope.
Flashings against a neighbour's wall bring in the Party Wall etc. Act 1996. Its section 2(2)(j) allows cutting into the adjoining owner's building to set in a flashing for a wall built against theirs. Notice is the building owner's job, and 14 days of silence from the neighbour counts as dissent, which calls in surveyors. Terraces and semis, where the flashing runs into a shared wall, are where this comes up.
A listed building adds a further check: listed building consent can be needed where the work changes the building's character, so ask the council before any flashing is altered, and read our page on leadwork on listed buildings.
06Leadwork · Lifespans
How long lead lasts and what it costs
Lead is chosen because it lasts, but a lifespan is never a promise, and we do not make one. MyJobQuote says correctly installed lead flashing can last for over 80 years, and over 100 years for higher codes, with minimal maintenance. The words that carry the weight are can and correctly installed: it describes a possibility under good fitting, not a guarantee for every roof.
MyJobQuote gives no VAT basis for its figures.
What moves a price is the length of flashing, the number of junctions, the lead code and above all the access, since MyJobQuote says its own range depends largely on whether scaffolding is required. Our written quote is one total after a survey, and scaffold is included in it; we arrange the licence with our scaffolder where it stands on the highway.
For repairs by length, Checkatrade lists lead flashing at £50 to £70 per metre (June 2026), a rate that cannot be multiplied into a total. Where one stretch has failed, a repair may be all that is needed, and we price a repair when the surrounding lead is sound. When it has all gone the same way, a whole new flashing is the better answer. For the full picture, see our lead work page.
Published costs vary, and they give a sense of scale and nothing more.
| Work | Figure | Source |
|---|---|---|
| Chimney lead flashing patch repair | Typically around £200 | MyJobQuote |
| Chimney lead flashing, full replacement | Averages around £570 | MyJobQuote |
| Full leadwork replacement | £350 to £920, depending largely on scaffolding | MyJobQuote |
Does lead flashing against a neighbour's wall need a party wall notice?
It can. Where the flashing needs a slot cut into the neighbour's building, section 2(2)(j) of the Party Wall etc. Act 1996 is the right involved, and serving notice falls to the building owner. Ask early, because notice periods run before the work can start.
Tell us what's wrong with the roof.
You'll get one written total price.