Copper on the roof: roof covering sheathing and building preservation

Take a walk through an old town and look up: the green roofs, spires and domes are copper. The metal has been used for roof covering for centuries, because it combines durability with formability and over time forms a tight, protective patina that can keep the building dry for generations. The coppersmith — in building often akin to the roofer — is the craftsman who lays, falls and maintains these roofs.

Copper corrodes very slowly in the open because the patina formed on the surface protects the metal underneath. A well-laid copper roof can last a very long time — far longer than most other roofing materials — and it is a major reason why churches and monumental buildings are traditionally thatched with copper. The material is also so malleable that it can be laid over curved surfaces spires and complex details where rigid plates cannot follow the shape.

Copper roofs are laid in strips that are joined with standing double folds. The fold is not just a tight joint — it is deliberately designed to absorb copper's movement when it expands in heat and contracts in cold. The strips are held with hidden clips (haft) that allow this movement instead of nailing the metal fast. That is precisely why you cannot just solder an entire roof together: a rigid joint would crack from the thermal movements.

Much of the work is in the details: flashings around chimneys, roof ties, spires and penetrations where water would otherwise penetrate. Here the copper is shaped by hand so it seals tightly around complex geometries. It is often in the details that a roof's durability is determined — poor flashing causes leaks, no matter how well the surface is laid. Gutters and downpipes are also made of copper, so the entire drainage is of the same metal.

On protected and conservation-worthy buildings, the coppersmith's work is also preservation work. Here it is about repairing and renewing with respect for the original craft: same material thickness, same false type, same details. Often an old patina must be preserved or matched, and new copper, which is shiny, will stand out until it has aged itself. Restoration work therefore requires both craft and understanding of the building's history.

This is what a copper worker must master

• 01Laying sheets with tight, movable standing double pleats
• 02Form coverings in hand around complex details
• 03Avoid galvanic corrosion against other metals.
• 04Produce gutters and downpipes in copper
• 05Repair and restore historic roofs responsibly

“A copper roof is not measured in years but in generations — if the seams are laid correctly.”