What is the weight of a square metre of Code 4 lead?

In the UK, Code 4 rolled lead sheet has a nominal weight of 20.41 kg per square metre ($kg/m^2$). It is the standard thickness used for most roof flashings.

Which lead code should I use for chimney flashing?

Code 4 is the most common choice for chimney flashings and vertical step flashings. Code 5 is often used for chimney 'backs' or 'aprons' where the lead is subjected to more water flow or movement.

How long should a piece of lead flashing be?

Individual pieces of lead flashing should never exceed 1.5 metres in length. Lead expands and contracts significantly with temperature; longer pieces will eventually buckle or crack under thermal stress.

What is patination oil and why is it used?

Patination oil is applied to new lead to prevent white carbonate stains (lead oxidation) from forming and washing down onto tiles or brickwork. It ensures the lead develops a uniform, grey, protective patina.

What is the weight of a square metre of Code 4 lead?

In the UK, Code 4 rolled lead sheet has a nominal weight of 20.41 kg per square metre ($kg/m^2$). It is the standard thickness used for most roof flashings.

Which lead code should I use for chimney flashing?

Code 4 is the most common choice for chimney flashings and vertical step flashings. Code 5 is often used for chimney 'backs' or 'aprons' where the lead is subjected to more water flow or movement.

How long should a piece of lead flashing be?

Individual pieces of lead flashing should never exceed 1.5 metres in length. Lead expands and contracts significantly with temperature; longer pieces will eventually buckle or crack under thermal stress.

What is patination oil and why is it used?

Patination oil is applied to new lead to prevent white carbonate stains (lead oxidation) from forming and washing down onto tiles or brickwork. It ensures the lead develops a uniform, grey, protective patina.

Lead Sheet & Flashing Calculator

Precision weight and roll estimation for UK roofing projects.

Total Flashing Length (m)

Roll Width (mm)

Lead Code

Lead Estimation

UK Lead Usage:
- **Code 3:** Light work, soakers.
- **Code 4:** General roof flashings (Standard).
- **Code 5:** Flat roofs, dormers, and large valleys.

Leadwork Masterclass: Codes, Weights & Expansion

The Gold Standard of Waterproofing

Rolled lead sheet has been used in the UK for centuries. It is unparalleled for its longevity and ability to be 'bossed' or dressed into complex shapes around chimneys, valleys, and roof intersections.

Our **lead calculator** simplifies the buying process by converting your measurements into the total weight (kg), which is how most UK merchants sell rolled lead.

UK Lead Code Chart

Code 3 (Soakers)1.32mm / 14.97kg/m²

Code 4 (Flashing)1.80mm / 20.41kg/m²

Code 5 (Valley)2.24mm / 25.40kg/m²

Managing Expansion

Lead is a soft metal with a high coefficient of thermal expansion. If you fit lead in long, continuous runs without 'laps', it will move, buckle, and eventually crack. Always follow the **Lead Sheet Association (LSA)** guidelines:

Max length for Code 4: 1.5 Metres
Minimum lap between pieces: 100mm to 150mm

Step Flashing

Used where a pitched roof meets a brick wall (like a chimney or gable). The lead is cut into 'steps' to follow the mortar lines of the brickwork, providing a watertight seal.

Hallclips & Wedges

Never use mortar alone to hold lead into a brick joint. Use lead wedges or 'Hallclips' to mechanically lock the lead into the wall before pointing with mortar or specialist lead sealant.

Pro Tip: Patination Oil

Always apply patination oil to new lead flashings immediately after installation. This prevents the formation of white carbonate, which can wash off and ruin the appearance of your tiles or new brickwork.

Roof Leadwork FAQ

Technical Disclaimer

Lead is a heavy and hazardous material. Always wash your hands after handling lead and follow appropriate manual handling procedures. All leadwork should be installed in accordance with BS EN 12588.