Lead Code 5: When to Specify Heavier Gauge Lead for Roofing

Lead Code 5, correctly referred to as Code Red under BSEN 12588:2006, is one of the most versatile grades of lead available. While Code Blue (Code 4) covers most standard domestic flashing work, there are details where Code Red is the right specification. Getting this decision right matters for performance, longevity, and cost. This guide explains when Code Red is needed, what it covers, and how to order the correct thickness.

Code 5 and Code Red: Understanding the Terminology

The roofing trade still widely uses the old numeric code system, Code 3, Code 4, Code 5, but BSEN 12588:2006 replaced this with a colour code system. Code 5 maps directly to Code Red. Abbey Metals supplies lead to the colour code standard, so understanding both references helps when reading specifications or ordering from different sources.

• Code Red (Code 5): thickness 2.00mm to 2.24mm
• Code Blue (Code 4): thickness 1.75mm to 1.80mm
• Code Yellow (no numeric equivalent): thickness 1.50mm to 1.59mm

Abbey Metals stocks Code Red in two specific thicknesses: 2.00mm and 2.24mm. The 2.24mm thickness is the one traditionally referred to as Code 5 in the old numeric system. Both sit within the Code Red range under BSEN 12588:2006. For a full comparison of all colour codes and their numeric equivalents, see the Abbey Metals Lead Sizing Comparison guide.

The Over-Specification Case for Code Red

One of the less well-known aspects of the colour code system is the over-specification saving it makes visible. When roofers and specifiers default to the old numeric maximum, they often order heavier lead than the detail requires. For Code Red, the difference between the minimum usable thickness (2.00mm) and the traditional Code 5 maximum (2.24mm) represents a 12% over-specification saving.

In practical terms, if your detail calls for Code Red and the minimum thickness is sufficient, ordering 2.00mm rather than 2.24mm gives a material saving without any compromise on performance. For larger orders, that saving adds up. If you are not sure which thickness is correct for your detail, contact Abbey Metals before ordering.

For a broader look at how the colour code system compares to the numeric system across all grades, see our guide Understanding Lead Codes: Code 4 vs Code 5 for Roofing Applications.

When to Specify Code Red Instead of Code Blue

The decision to move from Code Blue to Code Red is driven by the detail, the exposure level, and the width of lead required. Code Blue handles most standard domestic flashing applications well. Code Red becomes the correct specification in the following situations.

Wider Details

As the width of a lead detail increases, a heavier grade provides better stability and resistance to thermal movement. Where a detail requires a wider piece of lead than Code Blue handles well in a single run, Code Red is the appropriate step up. Abbey Metals stocks Code Red in widths from 390mm to 1000mm to cover larger details that Code Blue widths do not suit.

Parapet and Box Gutters

Parapet gutters and box gutters collect and channel significant volumes of water. They are also difficult to access for repairs, so longevity matters more than on standard flashing details. Code Red is the standard specification for these details, where the additional thickness provides durability and better resistance to the mechanical stress of water movement and thermal cycling.

Valley Linings

Lead valleys collect water from two roof slopes and channel it to the eaves. The volume of water, combined with the length of the run and the thermal movement involved, makes Code Red a common specification for valley linings. The 2.0 metre maximum install length for Code Red also suits longer valley runs better than the 1.5 metre limit that applies to Code Blue.

Dormer Cheeks and Roofs

Dormer cheeks are vertical lead surfaces exposed to direct weather on three sides. The combination of exposure, the size of the lead sheet required, and the need for a long service life makes Code Red a common specification for dormer cheeks and dormer roofs. Vertical cladding details generally benefit from the additional thickness and stiffness that Code Red provides over Code Blue.

Back Gutters and Aprons

Back gutters behind chimney stacks and large apron flashings handle concentrated water loads at critical junctions. Where these details are wider than a standard flashing or sit in an exposed location, Code Red gives better durability. On larger chimneys or in exposed upland locations, upgrading to Code Red on the back gutter is a sound decision even if the step flashings remain Code Blue.

Hip and Ridge Flashings

Hip and ridge flashings sit at the highest points of the roof and are exposed to wind, rain, and temperature extremes from all directions. Code Red is appropriate for these details, particularly on exposed properties or where the hip or ridge run is longer than a standard domestic detail.

Heritage and Listed Buildings

On heritage properties and listed buildings, specifications often call for heavier gauge lead to match original materials and provide a service life in keeping with the building. Code Red is frequently specified for chimney flashings, back gutters, and other details on historic structures where longevity is the primary consideration.

Code Red Install Lengths and Area Limits

Code Red allows a longer maximum install length than Code Blue, which is one of the practical advantages of the heavier gauge on larger details.

• Code Red 2.00mm: maximum install length 2.0 metres, maximum fitted area 1.00m2
• Code Red 2.24mm: maximum install length 2.0 metres, maximum fitted area 1.20m2
• Code Blue (Code 4): maximum install length 1.5 metres

Install in line with BS6915 and BS5534. These limits must be observed regardless of the detail. Exceeding maximum lengths causes thermal stress, cracking, and eventual failure at fixing points.

Widths Available from Abbey Metals

Abbey Metals stocks Code Red in widths of 390mm, 450mm, 510mm, 600mm, 760mm, 900mm, and 1000mm. This range covers the full spectrum of details where Code Red is specified, from wider cover flashings and aprons through to large valley linings and dormer cladding. If your project requires a non-standard width or a specific cut length, contact the team to discuss your requirements before ordering.

Fixing and Finishing Code Red Lead

The fixing principles for Code Red are the same as for any lead grade. Never nail through the face of the sheet. Use lead clips to secure free edges, wedges to hold upstands in raked mortar joints, and wood roll to divide flat sheet areas into bays. Allow for thermal movement at every detail by keeping piece lengths within the limits above.

Apply patination oil to all exposed Code Red surfaces immediately after installation. Newly installed lead produces lead carbonate run-off that stains tiles, slates, and masonry. One application of patination oil at installation prevents this by accelerating the formation of a stable surface oxide. Abbey Metals stocks patination oil for use with all lead grades.

For full installation guidance covering fixing methods, thermal movement, and the full range of roof leadwork details, read our post Professional Roof Leadwork: Installation Guide for UK Roofers.

Frequently Asked Questions