Roof leadwork
In short
Lead is the traditional material for every awkward junction on a roof and, correctly detailed, it outlasts almost everything around it. Almost all failed lead failed for the same reason: pieces run too long, so thermal movement fatigued and split them.
Also called: Lead roofing · Lead flashing · Leadwork repair · Lead valley and gutter
Signs you need this
- A split or crack in lead, usually across the middle of a long piece
- Lead flashing lifted, rolled or pulled out of its joint
- Flashing tape or bituminous paint over lead
- White powdery corrosion on the lead surface
- Lead visibly thinned or torn at a fixing or an edge
- A leak at a junction where the lead looks intact from the ground
Lead has been used on roofs for centuries because nothing else does the same job. It can be dressed by hand into any shape, it is completely impervious, it does not degrade in UV, and it develops a protective patina that stops further corrosion. Properly detailed lead on a roof will run for a hundred years.
The catch is that lead moves. It has a high coefficient of thermal expansion and it is soft, so a piece that is restrained at both ends and heated and cooled through the seasons will work-harden and eventually crack. That single fact explains the overwhelming majority of failed leadwork, and it is why maximum piece sizes exist.
The rule in practice is that pieces are kept short and lapped rather than run continuously. For code 4 flashings that means lengths in the order of 1.5 metres, with a lap at each joint so the sheet can move. A long unbroken run looks tidier and costs less in labour, and it splits — always across the middle, usually within ten to fifteen years. When a roofer says the lead was 'done properly' a decade ago and it has cracked, this is almost always why.
Code — the thickness — is the other specification that matters. Lead sheet is sold by code number, and the right code depends on the position and the exposure: code 4 is a normal minimum for flashings and soakers, while back gutters, valleys and anything taking real water volume usually want code 5 or heavier. Undersized lead fatigues faster and tears at the fixings.
Fixing and support are the third element. Lead should be laid on a sound, smooth substrate with no sharp arrises to cut into it, fixed at the head and left free to move at the tail, and held with fixings of a compatible metal — copper or stainless, never something that will set up a galvanic reaction. Lead dressed over a sharp edge thins at that point and fails there first.
Where lead genuinely is at the end of its life, the repairs worth having are lead-welded rather than patched with tape or paint. A properly welded lead repair is permanent and invisible; a strip of self-adhesive flashing tape over a split is a two-year measure that makes the eventual proper repair harder. The same goes for bituminous paint, which is the traditional way to hide failed lead and the reason so many leaks are found late.
What the job covers
- Lead specified by code appropriate to its position
- Pieces sized and lapped correctly for thermal movement
- Chases raked, wedged and pointed rather than sealed
- Sound substrate and no sharp arrises under the lead
- Compatible fixings — copper or stainless, never ferrous
- Lead-welded repairs where a sound sheet has localised damage
What it costs
We don't publish a price for this yet, because a number pulled out of the air is worse than no number at all — your roofer has to honour it. On roofing it would also be close to meaningless: access is often the biggest single factor, and it varies enormously house to house. You'll get a firm price for your actual job when they ring you back, before any work starts. The quote itself is free and there's no obligation either way.
Common questions
How long should lead last?
Correctly specified and correctly sized, a very long time — a century is realistic on a well-detailed roof. Lead that fails in ten or fifteen years has nearly always been laid in pieces that were too long, so thermal movement fatigued it. It is a workmanship failure rather than a material one.
Why does lead split in the middle?
Because it is restrained at both ends and moves a great deal with temperature. Every warm day it expands, every cold night it contracts, and if it cannot move freely the stress concentrates in the middle of the run until it work-hardens and cracks. Keeping pieces short with laps between them lets it move without stressing.
Can lead be repaired or does it need replacing?
A sound sheet with localised damage can be lead-welded, which is a permanent, proper repair. What is not a repair is flashing tape, mastic or bituminous paint — those hide the split, hold water against the lead and make the eventual replacement harder. If the sheet is fatigued along its length, welding one crack just moves the failure.
Is lead being replaced by modern alternatives?
Sometimes, and there are good proprietary flashing materials that suit particular situations, especially where lead theft is a concern. But for chimney weatherings, valleys and complex junctions on a traditional roof, correctly detailed lead is still the benchmark — and on a listed or conservation-area building it may be what is required.
Need this doing in Macclesfield?
Tell us the job and it goes straight to our local roofer — one call back, usually the same day. Free quote, no obligation.