A table of the six lead codes with their thickness, weight and colour mark, the one pairing that is fixed (soakers), and the questions to put to a quote that says only 'lead flashings' without naming a code.
Open a quote for leadwork and somewhere you will see a number: Code 4, Code 5, sometimes just 'code 5 lead'. It looks like a grade, as if a higher number meant a better product. It does not. A lead code is a way of naming how thick a sheet of lead is, and therefore how much it weighs, and the right sheet for a job depends on the detail it is protecting.
Lead is the metal that seals the awkward junctions of a pitched roof, such as the foot of a chimney, a valley between two slopes or the joint against a party wall. It is cut, folded and dressed to the shape of each junction, so the thickness matters for how it moves and how long it lasts. This post sets out the six codes in a single table, explains the colour marks that tell the sheets apart, and is plain about the one pairing that is settled: Code 3 is for soakers. For every other flashing, valley or flat area, the code is something the specification fixes for that roof. If your leadwork is the problem, our lead roofing page shows how the work is done.
What a lead code actually measures
Sheet lead is sold in codes numbered 3 to 8. Each code stands for a nominal thickness in millimetres and a weight per square metre. A higher number means a thicker, heavier sheet, nothing more. There is no quality ladder in it: a Code 5 sheet is not a better metal than a Code 4, it is simply a thicker piece of the same metal.
Thickness matters because lead is soft and moves with the weather. It expands in warm spells and contracts in cold ones, and a thin sheet laid across too wide a run can crease and eventually crack. A thicker sheet resists that for longer, but it is also heavier, harder to dress into a tight fold and dearer to buy. The art is in matching the sheet to the job.
Here are the six codes as Royston Lead publishes them for its cast lead sheet:
| Code | Sheet thickness (mm) | Mass (kg/m²) | Colour mark |
|---|---|---|---|
| 3 | 1.32 | 14.97 | Green |
| 4 | 1.80 | 20.41 | Blue |
| 5 | 2.24 | 25.40 | Red |
| 6 | 2.65 | 30.05 | Black |
| 7 | 3.15 | 35.72 | White |
| 8 | 3.55 | 40.26 | Orange |
Read across a row and you have the whole identity of a sheet. The steps between codes are not even: Code 3 to Code 4 adds 0.48 mm, Code 7 to Code 8 adds 0.40 mm. That is why two neighbouring codes can feel alike in the hand yet carry a clearly different weight when a full roll is lifted onto a scaffold.
Reading the colour marks
The colour mark is a shorthand. Each code has its own colour, so a roofer or a buyer can tell a Code 4 sheet from a Code 5 sheet at a glance without reaching for a micrometer. On the table above the sequence runs green, blue, red, black, white, orange as the codes climb from 3 to 8.
Useful as that is on a delivery, it comes with limits you should know about:
- The mark identifies the code of the sheet when it is new. It tells you what was bought, not what has happened to the lead since.
- Lead that has been on a roof for a few seasons weathers to a dull grey, so the colour of an installed flashing is no guide to its code.
- Two codes can look close in the hand. Code 4 and Code 5 differ by less than half a millimetre, which you will not see on a folded edge.
- A quote that names a colour but no code leaves you with a guess. Ask for the code, the thickness or both.
If you want to confirm what is going onto your roof, ask to see the roll before it is cut, with its mark on it. That is a perfectly ordinary request for the person paying for the work. On a re-lead where the old sheet is coming off, the thickness of the sheet you are replacing can be measured with callipers on a cut edge, which is more reliable than any guess made from the ground.
Code 3 and the soaker rule
Of all the questions about lead codes, this has the firmest answer. Royston Lead's own table of uses says Code 3 is "Recommended for lead soakers only". A soaker is a small, folded piece of lead, usually rectangular and bent to an L, that is slid beneath the tiles or slates beside a chimney or wall. It is a hidden part, set in beside the stepped flashing, and it never carries a large expanse of water on its own. Each soaker is tiny next to the flashing that covers it, and a run of them is laid one per course.
Code 3 is the thinnest sheet in the range, which suits a small piece that is cut to size and folded many times. The recommendation stops at soakers. Nothing in it extends to a flashing, a valley or a flat area, and for those the code is set separately, detail by detail.
This is where a lazy quote shows itself. If a quote describes new soakers and flashings at a chimney and gives one thickness for the lot, it is worth asking why. A soaker can be Code 3 and the flashing over it a different code; they are different parts doing different work. Our short answer on what lead soakers are explains how they sit behind a flashing.
Every other detail: the specification sets the code
Beyond soakers, no single code is right for a whole house, and no two houses share quite the same set of junctions. Royston's brochure lists the details that sheet lead is used for, and the list is a long one, running from the smallest hidden piece to a whole roof:
- Soakers.
- Cover flashings, chimney flashings, hip flashings and ridge flashings.
- Pitched valley gutters and box valleys.
- Dormer roofs and dormer cheeks.
- Flat roofing.
- Parapet walls.
- Most work on historic or listed buildings.
For all of these apart from the soaker, the code comes from the specification for the roof: the document that sets out each detail, its materials and its dimensions. A quick code-for-each-job chart would mislead you, because a valley's thickness turns on how long the run is, the pitch, how exposed the roof sits and how the joints are formed, and a chart pretends to certainty that the roof itself has not given.
What you can reasonably expect, as a householder, is that the specification states the code against each detail, and that the quote uses the same wording, even though the price itself is one total. Lead roofing in England follows BS 6915, which Approved Document C points to. On a historic or listed building, an architect or conservation officer may set the specification, and your roofer then works to it, with the consent route settled first. Our page on what code of lead to use for flashing takes one of these details further.
Weight, thickness and what it does to the roof
Because the codes go up in weight as well as thickness, the choice has a physical side effect. A square metre of Code 3 weighs 14.97 kg and a square metre of Code 8 weighs 40.26 kg, so the heaviest sheet is close to 2.7 times the lightest. On a small flashing the difference is a few kilograms. Across a whole flat roof or a large parapet gutter it is a real load for the structure below to carry, which is one reason the specification, and not the sheet merchant, decides.
Weight matters in a second way when the covering on a pitched roof is being changed. Under the Planning Portal, a new covering weighing 15 per cent or more above the old one needs building control approval. Approved Document A treats loading increased by more than 15% as a significant change. Flashings are a small share of the whole roof, so that test is about the main covering rather than the leadwork. A flat lead roof swapped for a different system is a case where the weights deserve a look.
For a sense of how long lead lasts, the figures are broad. HomeBuilding gives lead on a flat roof 60 to 100 years, and MyJobQuote has lead flashing lasting over 80 years, which should be read as a minimum and never as a pledge. A correct code, well dressed and well fixed, is part of getting there; a lifespan is not a warranty and no figure on this page is one.
What to ask when a quote says only 'lead'
A dispute over leadwork can begin with a quote that was vague about the sheet. You can head one off with a handful of questions put in writing before the work starts.
- Which code is each detail to be made in? A single answer for the whole roof is a reason to ask again.
- Are the soakers in Code 3, and is the flashing that covers them in a different code?
- Is the code named for the sheet itself, with its thickness in millimetres, so that it can be checked on delivery?
- Where there is a long valley or a wide flat area, how are the joints and the lengths of each sheet set out?
- Will the old lead be taken away, and will the old thickness be measured and noted before it goes?
- Where the building is protected by listing or sits within a designated area, who set the specification, and is consent in hand?
The quote that follows should be one total written price after the survey, and it should name the codes. If you decide to compare with another tradesperson, Citizens Advice suggests asking at least 3 traders to quote in writing; the comparison is only fair if each one names the same codes for the same details.
When leadwork is cracked, split or has stopped sealing a junction, the question is often repair rather than replacement. Our page on whether lead can be repaired sets out when it can.
