Rolled Lead Sheet Codes (3–8) Explained: Thickness, Uses & Best Practice
Choosing the right lead code is essential for durability and appearance. This practical guide covers thicknesses, weights and typical applications for Codes 3–8—aligned to our
Leadwork Standards.
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Quick Reference: Lead Codes, Thickness & Weight
| Code | Nominal Thickness (mm) | Approx. Weight (kg/m²) | Typical Uses (Guide) |
|---|---|---|---|
| 3 | 1.32 | 14.97 | Soakers (especially for tiled roofs), light-duty flashings where appropriate. |
| 4 | 1.80 | 20.41 | Most flashings (step, cover & chimney), soakers for slate roofs, tray linings with limited exposure. |
| 5 | 2.24 | 25.40 | Valleys, wider flashings, dormer cheeks/roofs, gutters with moderate spans. |
| 6 | 2.65 | 30.05 | Parapet/box gutters, flat/low-pitch coverings (in bays), large valleys and weatherings. |
| 7 | 3.15 | 35.72 | High-exposure gutters and flat coverings, wide weatherings, heritage details. |
| 8 | 3.55 | 40.26 | Heavy-duty/heritage coverings, parapets and large gutters in severe exposure zones. |
Note: Always size bays, laps and fixings to accommodate thermal movement. See our Leadwork Standards for limits on bay width/length and for correct underlay, fixings and joints.
How to Choose the Right Code (in 90 Seconds)
- Start with exposure & span. The wider the span or the harsher the exposure, the higher the code.
- Consider the detail. Flashings are typically Code 4; valleys and dormer roofs are often Code 5–6; larger flat coverings and parapet gutters lean to Code 6–8.
- Control movement. Keep bays modest, use wood-cored rolls/expansion joints, and never over-fix.
- Finish right. Use patination oil on visible weatherings and compatible sealants/clips to avoid staining and wind lift.
Best Practice Essentials (Aligned to Leadwork Standards)
1) Bay sizes & joints
Lead expands and contracts. To prevent fatigue cracking, keep bays within recommended limits and introduce
wood-cored rolls or expansion joints on larger areas. Specific limits and jointing details are in our
Leadwork Standards.
2) Underlay & substrate
Use a suitable underlay (e.g., geotextile or felt underlay designed for lead) on clean, ventilated substrates. Avoid sharp edges and ensure falls on gutters.
3) Fixings & clips
Fix at the top edges and allow the sheet to move. Use correct length copper/stainless fixings and compatible lead clips (heavier codes may need thicker clips).
4) Surface finish
Apply patination oil to new leadwork to reduce carbonate staining on adjacent materials and even out the patina as it forms.
Common Use Cases (What We Typically Specify)
- Chimney/abutment flashings: Usually Code 4, with correct laps and chase depths.
- Soakers: Code 3–4 depending on covering (tile/slate) and exposure.
- Valleys: Code 5 for typical spans; Code 6 for wider/high-exposure valleys.
- Dormer cheeks & roofs: Code 5–6 depending on size and exposure.
- Parapet/box gutters & flat coverings: Code 6–8 in well-detailed bays with expansion provision.
Need a project-specific spec? Review our Leadwork Standards and browse similar projects, then get in touch.
FAQs
What do lead “codes” actually mean?
They are standard thickness/weight grades for rolled lead sheet. Higher codes are thicker and heavier, suitable for wider spans and harsher exposure. See the table above for quick reference.
Which code is best for chimney flashings?
Code 4 is commonly used for most flashings. Always follow correct chase depth, laps and fixings, and confirm against our Leadwork Standards.
Do I need patination oil on new leadwork?
Yes—especially on visible weatherings next to stone, render or timber. It reduces staining and helps an even patina to form. You can source patination oil via The Lead Shop.
How long can a lead bay be?
Bay size depends on code, exposure and detail. Keep bays modest (narrow widths, conservative lengths) and incorporate rolls/expansion. See limits in our Leadwork Standards.
Is rolled lead sheet sustainable?
Lead is durable, repairable and recyclable. Correct detailing maximises service life and minimises waste.
