What makes code 4 lead different?

Code 4 lead (≈1.80 mm; ≈20.4 kg/m²) sits in the sweet spot between agility and stability. Within BS EN 12588 tolerances, it gives reliable thickness and weight—so laps, steps and arrises behave predictably across a job. Compared with lighter sheet, code 4 lead holds sharper lines on exposed edges; compared with heavier grades, it dresses without a fight on small geometry and tight step patterns.

9 essential uses for code 4 lead

1) Chimney step flashings

Code 4 lead is the default for step flashings on brick and stone. It holds crisp steps, tolerates daily temperature swing, and seats cleanly into chases. Keep rises consistent, avoid feathered edges at the drip, and maintain even cover across courses.

2) Chimney aprons

Front aprons want stiffness and a decisive arris. Code 4 lead lets you form a sharp drip line so water clears the face below. Where aprons widen or wind is severe, review spans and consider stepping to Code 5.

3) Soakers with step flashings above

When combining soakers and steps, many teams prefer soakers in a lighter gauge and use code 4 lead for the visible steps. This balances dressability under the covering with a crisp, stable line at the weathering.

4) Abutment flashings to pitched roofs

At wall-to-roof interfaces, code 4 lead forms reliable abutments that don’t oilcan. Keep laps generous, apply finishing oil after cleaning, and verify hose tests along the run—especially near corners.

5) Short aprons to dormers & roof windows

Short aprons benefit from the added mass and edge stability of code 4 lead. It keeps drips crisp without needing excessive working that thins the sheet.

6) Back gutters on modest chimneys

Where catchment is small and falls are good, code 4 lead can serve for back gutters. Keep beds smooth, laps disciplined, and outlets generous. If geometry grows or turbulence is high, move to Code 5 or 6.

7) Flashings to parapet abutments

Parapet interfaces demand clean lines across long views. Code 4 lead holds shape over time with correct restraint—clips or stainless strip set back from the edge, never rigid screws through movement zones.

8) Weatherings to small projections & upstands

Small service upstands, vent terminals and modest penetrations suit code 4 lead where a crisp finish matters and beds are short. Maintain falls and avoid ponding near seals.

9) Heritage repairs on delicate masonry

On sensitive façades, code 4 lead delivers crisp, repeatable detailing that photographs well and weathers gracefully when finished properly.

Where to step up a gauge

• Wide aprons in wind: consider Code 5 to reduce flutter and retain arrises.
• Valleys & box gutters: these are troughs—use Code 6 or 7. See valley gutters and box gutters.
• Parapet cappings: favor Code 6–7 with bay breaks and movement joints.
• Exposed coastal ridges: wind scouring and salt suggest heavier gauges plus careful restraint and underlay.

Sizing, laps & fixings that last

Step flashings: clean geometry & chase discipline

Chase discipline makes or breaks step flashings. Cut neat, consistent slots, clear dust before inserting the piece, and point or seal evenly to avoid point loads that telegraph through the sheet. With code 4 lead, you can form sharp arrises with minimal working—take advantage by pre-forming at the bench.

• Slot depth & pitch: consistent depth and angle improve seating and weathering.
• Sequencing: set out the first piece with absolute accuracy; subsequent steps will follow that reference.
• Edge hygiene: remove grit that would score the underside while dressing.

Chimney sets: aprons, soakers, step flashings & back gutters

Most domestic chimneys are delivered in four parts. Code 4 lead is ideal for the visible step flashings and the front apron; choose soaker gauge to suit the covering and consider stepping up at the back gutter if catchment is large.

1. Apron: decisive arris, even fall, generous lap to covering.
2. Soakers: consistent cover widths; coordinate with steps above.
3. Step flashings: neat chase work and uniform step geometry.
4. Back gutter: smooth bed, preserved free area at outlet; step to Code 5 or 6 as scope grows.

Safety: handling & COSHH essentials

Even at ≈20.4 kg/m², safe handling matters. Plan lift paths, avoid twisting while carrying, and store pieces flat. Wear gloves and observe hygiene to manage exposure risks. Dispose of rag waste responsibly and avoid contaminated run-off to gardens or drains.

• See: Manual Handling for Rolled Lead Sheet
• See: COSHH for Rolled Lead Sheet

Quick-buy basket: sheet + underlay + fixings + finish

FAQs — code 4 lead