# Zinc Cladding — Patina, Systems and Service Life

> Zinc cladding is titanium zinc sheet formed into standing seam, cassette or shingle facade panels that develop a protective patina and need no coating maintenance. Its service life depends on the rear face: the panel must sit over a ventilated and drained cavity, because zinc held against damp, unventilated backing corrodes from behind.

## 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

| Property | Typical specification |
| --- | --- |
| Standard | EN 988 |
| Thickness | 0.7mm — 1.0mm typical |
| Finish | Mill, pre-weathered grey, or pigmented |
| System | Standing seam, cassette, interlocking shingle |
| Backing | **Ventilated and drained cavity, always** |
| Fire class | A1, non-combustible, to EN 13501-1 |

## 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)**.

## Frequently asked questions

### Why must the back of a zinc panel be ventilated?

Zinc corrodes from the rear far faster than the front when moisture is trapped against it. The front develops a protective patina in open air; the back, held against a damp substrate with no airflow, has no such protection and corrodes through. Every zinc system therefore needs a ventilated and drained cavity behind it, and that requirement is non-negotiable rather than a refinement.

### What is pre-weathered zinc?

Zinc that has been chemically treated at the factory to produce the grey patina immediately, rather than waiting years for it to develop naturally. Natural mill-finish zinc weathers unevenly depending on exposure and rain run-off patterns, which on a single elevation can look like a defect. Pre-weathered material gives a consistent appearance from handover.

### Is zinc suitable for Indian coastal projects?

With care. Zinc performs well in most atmospheres but chloride exposure accelerates corrosion, and its life near the sea will be shorter than inland. Detailing matters more there: full rear ventilation, avoidance of standing water, and no contact with copper run-off, which attacks zinc rapidly. In severe coastal exposure a coated aluminium system is often the safer specification.

## Sources

- [EN 988](https://standards.cencenelec.eu/ords/f?p=CEN:105) — Zinc and zinc alloys — rolled flat products for building
- [EN 13501-1](https://standards.cencenelec.eu/ords/f?p=CEN:105) — Reaction to fire classification
- [IS 875 (Part 3)](https://standards.bis.gov.in/website/published-standards/department-wise) — Wind loads on buildings

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Source: https://hagerstone.com/materials/zinc-cladding