Metal wall cladding and feature panels

At a glance

Weights are computed as density times thickness; real sheet varies a little. 1.5 and 3 mm figures are in the weights table below. Dense metals get heavy fast: check what the wall and fixings will carry.

How thick, and why flatness is the real question

People ask how thick a metal wall panel should be. The honest answer is that thickness is one of several levers on flatness, and flatness is what the eye notices. A large, thin, highly reflective sheet under raking light will show every ripple. A thicker sheet, a backed or bonded panel, a folded stiffener or a textured face will hide them.

The visible effect is called oil canning. The Metal Construction Association, a US trade body, defines it as visible waviness in the flat areas of metal roof and wall panels, and treats oil canning, waviness, elastic buckling and stress wrinkling as the same thing. Its bulletin says the tendency can be reduced through attention to production, material selection, panel design and installation practice, and that no manufacturer, fabricator or installer can assure the total prevention of oil canning on a given project. That sentence belongs in a brief: it means the designer and the partner agree an acceptable appearance on a sample, rather than assume perfection.

What the bulletin does not give, and this sheet does not invent, is a thickness for a given panel size. Ranges depend on the metal, the finish, the size of the field and the backing, and are for the partner workshop to propose and prove on a large sample.

Three ways to fix a panel

The fixing decides whether the face is clean, whether the metal can move, and whether a damaged panel can be replaced. The table is a practice summary of the common methods; the partner workshop confirms which it uses and tests.

Whichever method is used, the metal moves with temperature (see thermal expansion of metals), so a long panel that is pinned rigidly at every point can distort. Dissimilar metals in contact can also corrode: see galvanic corrosion and dissimilar metals. Fixings should be chosen with fixings and fasteners for metalwork in mind.

Joints and weight

A joint between metal panels is a decision about tolerance. A tight butt joint shows every misalignment; a shadow gap or a recessed joint hides it and gives the metal room to move. Our tolerances for visible metalwork sheet covers what to ask for, and the gauge conversion sheet covers thickness language. Match the finish across panels with an approved sample: see metal finish sample approval.

Weight follows density. The table gives kilograms per square metre for three common thicknesses; multiply by area for a panel, and add the backing and rail. It is arithmetic, not a catalogue value: confirm the actual sheet with the partner.

Fire and safety on interior walls

For England, Approved Document B Volume 2 asks the surface of walls and ceilings in buildings other than dwellings to meet Table 6.1 classes of BS EN 13501-1. In the edition read: small rooms up to 30 m2 in non-residential accommodation, D-s3, d2; other rooms, C-s3, d2; other circulation spaces such as corridors, B-s3, d2. Paragraph 6.4 allows parts of walls in a room to be of lower performance, no worse than D-s3, d2, up to half the floor area and 60 m2 in non-residential accommodation.

If the panel is a composite with a core, the core decides the class, and paragraph 6.11 adds conditions for insulating core panels used inside: seal joints and service penetrations, use only class A1 cored panels in high fire-risk areas such as kitchens, and design the fixing for the chance that the panel delaminates. A solid metal sheet does not raise those questions, but the supplier should still state the class of what is quoted. See also our real metal, laminate and metal-effect finishes sheet and fire performance of wall panelling.

External walls are different. Regulation 7(2) requires materials in the external wall of a relevant building (a storey at least 18 m above ground containing dwellings, an institution or a room for residential purposes, hotels included) to be class A2-s1, d0 or A1, with exemptions. A metal panel on the outside of such a building is a question for the project's fire engineer.

Finally, a heavy panel on a wall is a falling-hazard question as much as a fire one. Fixing to the structure behind it, and to the right backing in a stud wall, is for the partner workshop and, for a heavy or high panel, a structural engineer.

Wall panels [ref]: [brass / stainless 304 / aluminium] sheet [2] mm, [finish], overall panel size [ ] × [ ] mm, joints [shadow gap [ ] mm / recessed butt]. Flatness of the face to be judged on the approved full-size sample under [raking light at [ ] degrees], dated [date]. The supplier states in writing that oil canning cannot be wholly excluded and proposes the measures taken (thickness, backing, stiffeners, finish) before quotation.

Panels to be fixed by [concealed hook-on rail / bonding to a [ ] mm backing board / pins in slotted holes], designed and checked by [supplier] for the substrate [wall type], the panel weight [ ] kg and likely impact. Fixing drawings are submitted for approval. Dissimilar metals in contact are isolated. Panels are replaceable without damage to adjacent panels.

Wall surface class of the panel build-up to be not worse than [C-s3, d2] to BS EN 13501-1 in [room], as required by the project fire strategy. The supplier submits the classification report for the exact build-up, including any core and adhesive, before ordering. Cored panels are sealed at joints and penetrations and are not used in high fire-risk areas unless A1 cored.

Panel weight [ ] kg including backing, confirmed in writing by [supplier]. Handling and installation method to be agreed with [contractor] before delivery.

Standards and sources

• Approved Document B, Volume 2 (England): 2019 edition incorporating 2020 and 2022 amendments, collated with 2025, 2026 and 2029 amendments; Table 6.1, paras 6.4, 6.11, 12.15 read 7 Nov 2026. Check which amendments apply to your project.
• BS EN 13501-1:2018: BSI Knowledge, 7 Nov 2026: Current, published 31 January 2019. Not read.
• Metal Construction Association: oil canning bulletin: web summary read 7 Nov 2026; the full report was not opened. US trade body; written for roof and wall systems.

Questions we are asked

How thick should a metal wall panel be?

There is no single figure. Thickness is one of several levers on flatness, with backing, stiffening folds, finish and fixing. The partner workshop should propose a build-up for your panel size and finish and prove it on a full-size sample.

What is oil canning and can it be avoided?

Visible waviness in the flat areas of metal panels. A US trade body's bulletin says careful production, material selection, panel design and installation reduce it, but that no one can guarantee total prevention. Agree an acceptable appearance on a sample.

Can a metal feature panel be fixed without visible fixings?

Yes: concealed hook-on rails or bonding to a backing board. Each has trade-offs for movement and replacement, summarised in the table.

What fire class does a metal wall panel need?

In England, Approved Document B asks for D-s3, d2 in small non-residential rooms up to 30 m2, C-s3, d2 in other rooms and B-s3, d2 in other circulation spaces, with limited lower-performance areas allowed. The panel's own classification report decides whether it meets that; cored panels have extra conditions.

How heavy is a brass or stainless wall panel?

Density times thickness: 2 mm brass is about 16.9 kg per square metre, 2 mm stainless 304 about 15.8, 2 mm aluminium about 5.4, before backing and rails.