Zinc Cladding — Patina, Systems and Service Life

What it is

Titanium zinc sheet — zinc alloyed with small amounts of titanium and copper — formed into standing seam, cassette or shingle cladding. It develops a protective patina in service and is one of the longest-lived facade metals.

Specification at a glance

Why it gets specified

Very long service life in normal atmospheres, with a self-healing patina that protects the metal rather than degrading it.

No coating to maintain. Unlike painted metal there is no film to chalk, fade or recoat, which removes a whole category of facade maintenance.

Formability. Zinc takes complex curves, seams and shingle patterns that stiffer metals resist.

The rear-face rule

This is the single thing that determines whether a zinc facade lasts:

• Continuous ventilation behind the panel, open at the bottom and top
• A separating layer where zinc meets timber, concrete or plaster
• No standing water anywhere against the rear face
• No copper upstream. Run-off from copper flashings or pipes destroys zinc downstream of it

Where projects go wrong

• Sealed cavity behind the panel. The facade then corrodes from the back, invisibly, until it perforates.
• Copper and zinc on the same elevation with run-off from one onto the other.
• Fixed rigidly. Zinc has high thermal movement; clips must allow the panel to slide.
• Handled with bare hands in hot weather. Fingerprints can mark pre-weathered surfaces.
• Working the metal below about 10°C without warming, where zinc becomes brittle and cracks on folding.

Standards referenced

Rolled zinc for building under EN 988. Reaction-to-fire classification to EN 13501-1. Wind loading on cladding under IS 875 (Part 3).