Quick answer: An ACP sheet’s grade is defined by four things: total thickness (3 mm or 4 mm), aluminium skin thickness (0.5, 0.3 or 0.21 mm), core (PE or fire-retardant) and coating (PVDF or polyester). For exterior facades in Tamil Nadu and Kerala, the safe default is 4 mm with 0.5 mm skins and PVDF coating, with FR core for taller or public buildings. For interiors and signage, 3 mm with lighter skins and polyester coating is often enough.
What an aluminium composite panel is made of
An aluminium composite panel (ACP) is a sandwich:
- Top aluminium skin, coated with paint (PVDF or polyester) and covered with a peel-off protective film.
- Core, either polyethylene (PE) or a mineral-filled fire-retardant (FR) compound.
- Bottom aluminium skin, usually with a simple service coat.
The standard sheet size is 1220 x 2440 mm, often called the “8x4” sheet. Longer lengths are offered by many manufacturers for tall panels.
When people say “ACP grade”, they usually mean a mix of all four specifications below. A sheet is only as good as its weakest one.
Thickness: 3 mm vs 4 mm
| 3 mm ACP | 4 mm ACP | |
|---|---|---|
| Typical use | Interiors, signage, column cladding, sheltered areas | Exterior facades, building elevations |
| Flatness on large panels | Can show waviness (“oil canning”) | Stays flatter |
| Resistance to dents | Lower | Higher |
| Wind load on height | Limited | Better suited |
| Cost | Lower | Higher |
Thicker sheets exist (6 mm and above) for special uses, but for most facade work in our region the choice is between 3 mm and 4 mm.
Skin thickness: the part people forget
The aluminium skin carries most of the strength and all of the weather protection. Two sheets can both be “4 mm” and behave very differently.
- 0.5 mm skin: the usual specification for exterior facades. Stiffer, more dent-resistant, better for large panels and routed trays.
- 0.3 mm skin: common for signage, interiors and some exterior fascia in sheltered spots.
- 0.21 mm skin and thinner: budget interior grade. Not suited for exposed exterior panels.
Tip: if a quote says only “4 mm ACP”, ask “what skin thickness?” The answer tells you a lot about the product being offered.
Core: PE vs FR
PE (polyethylene) core
Light, easy to route and fold, and lower in cost. Widely used for interiors, signage and low-rise exterior work.
FR (fire-retardant) core
A mineral-filled core that burns far less readily than plain PE. It costs more and is slightly heavier. It is the responsible choice for multi-storey buildings, hospitals, schools, malls and other public buildings, and wherever the approving authority requires it. Always confirm the requirement with your architect or fire consultant before ordering, and ask for the manufacturer’s fire test documents for the exact product.
Coating: PVDF vs polyester
| PVDF coating | Polyester coating | |
|---|---|---|
| UV and colour stability | Very good | Moderate |
| Chalking and fading outdoors | Slow | Faster on sun-facing walls |
| Best use | Exterior facades | Interiors, signage, shaded areas |
| Cost | Higher | Lower |
In Coimbatore, Madurai or Kochi, a west-facing wall gets intense afternoon sun for most of the year. Polyester-coated dark colours on that wall can look tired well before PVDF would. If the ACP faces the sun or the sea, specify PVDF.
Matching grade to the job
| Application | Suggested starting specification |
|---|---|
| House front elevation, exterior | 4 mm, 0.5 mm skins, PVDF, PE or FR as required |
| Multi-storey commercial facade | 4 mm, 0.5 mm skins, PVDF, FR core |
| Shop fascia and signage band | 3 mm or 4 mm, 0.3–0.5 mm skins, PVDF if sun-facing |
| Interior column or wall cladding | 3 mm, 0.21–0.3 mm skins, polyester |
| Soffit and ceiling panels | 3 mm or 4 mm depending on span and exposure |
| Coastal sites (Kerala coast, Chennai, Thoothukudi) | 4 mm, 0.5 mm skins, PVDF, with a corrosion-protected sub-frame |
These are starting points. Panel size, wind exposure and building height can change the answer, which is why we specify after seeing the site.
Things that matter as much as grade
- Sub-frame: a premium sheet on a rusting frame will still fail. Use aluminium or properly galvanised steel sections.
- Fabrication: routed and folded trays (cassettes) need correct routing depth so the skin does not crack at the fold.
- Installation direction: metallic and some special finishes can look slightly different depending on direction. Panels should all be fixed following the arrows on the protective film.
- Film removal: the protective film should be removed soon after installation. Film left baking in the sun becomes hard to remove and can leave residue.
- Joints: sealed joints need good-quality weather sealant with backer rod; open-groove designs need a proper drainage plan behind.
How to verify what you are buying
- Ask for the brand, product name, thickness, skin, core and coating written on the quote.
- Ask to see the product data sheet.
- Check printing on the back of the sheets on delivery, where the manufacturer provides it.
- Keep an offcut. Skin thickness can be measured on it.
A quick buyer’s checklist
Before you approve an ACP order, confirm in writing:
- Total thickness: 3 mm or 4 mm
- Skin thickness on both faces
- Core: PE or FR, with test documents for FR
- Coating: PVDF or polyester, and the colour or finish code
- Brand and product name
- Sheet length, to reduce joints and wastage on tall panels
- That all sheets for one elevation come from the same batch, so the colour matches
How Cladex helps
At Cladex Elevations, Er. Sanjay M. and Er. Aravind M. specify the ACP grade for each part of your building separately, so you do not overpay for interior areas or under-specify the sun-facing facade. We write the full specification into the quote and explain each choice in plain language.
Send us a photo or drawing on WhatsApp for a free, site-measured quote with the right ACP grade for each surface.