Lead Flashing: The Complete Guide

Lead flashing is one of those roofing components most homeowners never think about — until it fails and water starts getting in. Here's a comprehensive guide.

What Is Lead Flashing?

• **Chimney stacks** — lead seals all four sides where the chimney meets the roof
• **Dormer cheeks and tops** — where a dormer window protrudes from the roof slope
• **Velux and roof windows** — factory-made flashing kits seal around the frame
• **Abutment walls** — where a lean-to, extension, or outbuilding roof meets a wall
• **Valleys** — in some roofing systems, lead valley liners are used

Why Lead?

• **Malleable** — lead can be shaped precisely to any profile
• **Self-annealing** — it can be worked multiple times without cracking
• **Durable** — correctly installed lead can last 50–100 years
• **Proven** — no modern substitute has matched its track record

What Is Code 4 and Code 5 Lead?

• **Code 4** (1.80mm thick) — used for step flashings, cover flashings, and soakers
• **Code 5** (2.24mm thick) — used for more exposed applications like chimney back gutters and valley liners
• **Code 6+** — used in very demanding applications like flat roof weathering

Signs of Failed Flashing

• Water stains on ceilings near chimneys, dormers, or skylights
• Visible lifting, cracking or gaps in the lead
• Lead that has slipped out of the mortar joint
• Mortar around flashings that is crumbling or missing

Repair vs Replacement

• The lead has significantly moved out of position
• It is very old and showing widespread cracking
• The mortar joints holding it in place have failed across a significant length

...full replacement is usually the more economical choice.

Alternatives to Lead

In some situations, lead-free flashings such as leadwork tape, GRP flashings, or butyl rubber flashings are used. These are appropriate for some applications but rarely match the lifespan of traditional lead. We will always advise on the best solution for your specific situation.

For lead flashing repair or replacement across Coventry and surrounding areas, contact Reliable Roofing Services.