# Solid Aluminium Panel — Specification and Use

> A solid aluminium panel is a single sheet of aluminium alloy folded into a cassette and hung on a sub-frame, with no polymer core or bonding line. Being one non-combustible material through its thickness, it is specified over ACP where fire performance, deep folds, complex geometry or absolute flatness govern.

## What it is

A **single sheet of aluminium alloy**, folded into a cassette and hung on a
sub-frame. Unlike ACP there is no polymer core and no bonding line — the panel
is one material through its whole thickness.

That single fact drives most of the specification decisions around it.

## Specification at a glance

| Property | Typical specification |
| --- | --- |
| Alloy | 3003, 3105 or 5005 to IS 737 |
| Thickness | 2mm — 4mm for cassette cladding |
| Finish | PVDF coil coating, or anodised |
| Coating standard | AAMA 2605 for the highest weathering class |
| Fire classification | A1 / non-combustible to EN 13501-1 |
| Panel format | Cassette with folded returns, rear stiffeners as required |

## Why it gets specified

**Fire performance is not a discussion.** The panel is metal through its
section, so there is no core grade to argue about, no test certificate to
match against a delivered batch, and no substitution risk at supply stage. On
high-rise, healthcare and high-occupancy buildings this removes the single
most contested item in a facade submission.

**It holds a fold.** Deep returns, sharp corners, tapered panels and curved
geometry are achievable in solid sheet in ways a composite panel resists,
because there is no core to delaminate at a tight radius.

**Flatness.** On a prestige elevation viewed in raking light, a well-detailed
solid aluminium cassette with rear stiffeners reads flatter than most
alternatives.

## What drives the cost

Sheet thickness · alloy · finish class, with PVDF and anodised costing more
than polyester · panel size and the number of folds · rear stiffener extent ·
whether panels are flat, curved or tapered · sub-frame complexity · building
height and access.

Solid aluminium typically lands **above ACP and below** most natural stone
per square metre, but the gap narrows once ACP is specified in A2 grade.

## Where projects go wrong

- **Thin sheet on a large panel.** The result is oil-canning — visible waviness
  that no amount of site adjustment removes. It is a design error, fixed at
  panel-size and stiffener stage, not on site.
- **Stiffeners bonded with the wrong adhesive.** A facade in Indian summer sun
  runs far hotter than ambient. The bond must be rated for that service
  temperature or stiffeners debond and the panel bellies out.
- **Assuming a non-combustible panel makes a compliant facade.** It does not.
  Cavity barriers and insulation grade still govern.
- **Leaving the finish class unnamed.** "Powder coated" spans products lasting
  five years and products lasting twenty-five. Name the resin class.

## Standards referenced

Sheet alloy and temper under **IS 737**. Reaction-to-fire classification to
**EN 13501-1**. High-performance organic coating performance to **AAMA 2605**.

## Frequently asked questions

### When is solid aluminium specified instead of ACP?

Where fire performance governs, where the panel must be folded into deep returns or complex geometry, and on prestige elevations where absolute flatness matters. Solid aluminium is a single metal sheet with no polymer core, so the core fire debate does not arise at all. It costs more per square metre than ACP and is heavier to handle, which is why ACP still dominates general areas.

### What thickness is used on a facade?

Commonly 2mm to 4mm for cassette panels. Thickness is driven by panel size, wind pressure and how flat the panel must stay: a large panel in thin sheet oil-cans, showing visible waviness across the face. Stiffeners bonded to the rear let a thinner sheet span further, but they must be bonded with a structural adhesive rated for the service temperature.

### Does solid aluminium avoid the cavity fire risk?

The panel does, but the assembly does not. Aluminium is non-combustible as a metal, yet a ventilated cavity behind any panel still behaves like a chimney. Cavity barriers at every compartment line and non-combustible insulation remain mandatory. Specifying solid aluminium and then omitting barriers produces a facade that is still non-compliant.

## Sources

- [IS 737](https://standards.bis.gov.in/website/published-standards/department-wise) — Wrought aluminium and aluminium alloy sheet and strip
- [EN 13501-1](https://standards.cencenelec.eu/ords/f?p=CEN:105) — Reaction to fire classification
- [AAMA 2605](https://fgiaonline.org/) — High-performance organic coatings on aluminium

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Source: https://hagerstone.com/materials/solid-aluminium-panel