In the UK, the thickness of lead codes is standardized mainly for applications like roofing, cladding, flashing, and weatherproofing. These are classified into “Lead Codes,” ranging from Code 3 to Code 8. Each lead code is linked to a specific thickness and weight per square meter.
These standards are set by the Lead Sheet Training Academy (LSTA) and comply with BS EN 12588, ensuring that the thickness and material quality remain consistent.
Lead codes play a crucial role because they help you select the right thickness for your project. Each lead code is linked to a specific thickness and weight. If you happen to use the wrong code—like opting for a thinner sheet when a thicker one is necessary—you could face some serious issues, such as:
Using the wrong code can leave the lead exposed to factors that cause it to break down much faster than it should.
British Standard Lead Sheet Codes
| Lead Code | Thickness (mm) | Weight (kg/m2) | Typical use |
| Code 3 | 1.32mm | 14.97 kg/m2 | Soakers / Light duty |
| Code 4 | 1.80mm | 20.41 kg/m2 | Light duty / general |
| Code 5 | 2.24mm | 25.40 kg/m2 | General / vertical / pitched |
| Code 6 | 2.65mm | 30.10 kg/m2 | Large roofs |
| Code 7 | 3.15mm | 35.72 kg/m2 | Heavy duty |
| Code 8 | 3.55mm | 40.26 kg/m2 | Heavy duty |
The way we classify lead sheets into standardized codes—like Code 3, Code 4, and so on—has a rich history tied to the use of lead in construction. However, the modern lead code system really took shape in the 20th century, particularly in the UK, as a way to ensure consistency in manufacturing and installation practices.
Each code corresponded to:
Code 4 has become the standard choice for general flashing work.
Lead coding is really important these days because it makes things easier for architects and contractors when it comes to specifications. It helps cut down on mistakes at the job site and promotes safe, proper installations that meet the required standards.
The main European standard for lead sheet is:
BS EN 12588: Rolled Lead Sheet for Building Purposes
Key Features of BS EN 12588:
The lead codes are standardized across the UK and much of Europe, adhering to BS EN 12588.
Different areas outside of Europe tend to follow their own standards, which are usually based on weight or thickness instead of the “code” system.
Lead sheets that meet the BS EN 12588 standards should be clearly labelled at regular intervals along their length.
Each sheet must display:
The British/European standard it complies with.
A typical marking might look something like this:
BS EN 12588 – CODE 5 – 2.24 mm – 25.40 kg/m² – Manufacturer Name – Batch No.
Choosing the right code really hinges on several factors, and if you’re feeling uncertain, it’s a good idea to reach out to a qualified professional for some guidance.
Factors to Consider are:
Common Mistakes to Avoid
Using the right lead code is crucial for guaranteeing durability, weather resistance, and adherence to building standards particularly in roofing and construction.
We always advise contacting a professional if you are unsure.
Here at Leadworx we stock a range of products here in code 4. We buy from leading brands such as ALM and Calder Lead. If you need something made up in a different code. Please don’t hesitate to contact our team for a quote.
