Metal Thickness in Design: What Looks the Same on Paper but Changes Everything in Fabrication

At first glance, metal thickness often appears to be a minor detail on architectural drawings. A panel shown as 3 mm thick can look nearly identical on paper to one drawn at 5 mm. However, in real fabrication, metal thickness changes everything — from rigidity and weight to cost, finishing quality, and installation complexity.

Over the years, we’ve seen how gauge selection, when underestimated during design, leads to warping, visible oil-canning, unexpected weight issues, and avoidable rework on site. Conversely, we’ve also seen projects where over-specifying thickness added unnecessary cost without improving the final result.

Understanding how thickness affects fabrication is essential for designers who want predictable, high-end outcomes.

 

Why Thickness Matters More Than It Seems

Metal does not behave like a flat graphic element. Instead, it reacts to:

• ✔ Heat from welding and forming

• ✔ Its own weight over large spans

• ✔ Fastening methods and support conditions

• ✔ Finishing processes such as polishing or brushing

As a result, two panels that look identical in drawings can behave completely differently in real life simply because of a small change in thickness.

Rigidity: Preventing Oil-Canning and Warping

One of the most common issues we encounter is oil-canning — the visible waviness that appears on large flat metal surfaces.

This typically happens when:

• ✔ The metal is too thin for the panel size

• ✔ The panel is insufficiently supported

• ✔ Heat from welding or forming distorts the surface

Designers often specify thinner material to reduce weight or cost. However, if the thickness is insufficient, the surface will never appear perfectly flat regardless of fabrication skill.

A useful engineering reference for how material thickness affects stiffness can be found in standard sheet metal design principles from sources like The Fabricator:

👉 https://www.thefabricator.com/thefabricator/article/shopmanagement/sheet-metal-design-the-basics

Even small increases in thickness dramatically increase rigidity and reduce the risk of distortion.

Weight: When Panels Become Difficult to Handle

While thicker metal improves rigidity, it also increases weight quickly. This has a direct impact on:

• ✔ Handling during fabrication

• ✔ Transportation logistics

• ✔ Installation difficulty on site

• ✔ Structural support requirements

We have seen cases where panels were specified too thick, making them extremely difficult for installers to maneuver safely. In some instances, additional structural backing had to be added because the wall system was not designed to carry the weight.

Therefore, thickness must be balanced between rigidity and practical handling.

Cost: The Hidden Multiplier

Material cost increases linearly with thickness. However, fabrication cost does not.

Thicker material means:

• ✔ Longer cutting times

• ✔ More tool wear

• ✔ More labor during forming and welding

• ✔ Increased finishing time

As a result, increasing thickness from 3 mm to 5 mm may seem minor in drawings but can noticeably increase overall project cost.

On the other hand, going too thin often leads to rework, remakes, or visual rejection — which is even more expensive.

Finishing Quality: Why Thickness Affects Appearance

This is often overlooked.

During polishing, brushing, or patina application:

• ✔ Thin metal flexes under pressure

• ✔ Inconsistent pressure leads to inconsistent grain or reflection

• ✔ Surface imperfections become more visible

Thicker material remains stable during finishing, allowing for a more consistent architectural appearance.

This is particularly critical for:

• ✔ Brushed stainless steel

• ✔ Bronze and brass with directional grain

• ✔ Large decorative panels

Installation: Where Thickness Mistakes Show Up

Problems caused by incorrect thickness rarely show up in the shop. They show up during installation.

Common issues include:

• ✔ Panels that bend during fastening

• ✔ Visible waves after installation

• ✔ Fasteners pulling surfaces inward

• ✔ Difficulty aligning panels perfectly

By the time this happens, fabrication is complete and corrections are costly.

Lessons Learned from Real Projects

From experience, most thickness mistakes fall into two categories:

1. Under-specifying thickness

This leads to:

• ✔ Oil-canning

• ✔ Surface distortion

• ✔ Poor visual quality

• ✔ Installation struggles

2. Over-specifying thickness

This leads to:

• ✔ Excess weight

• ✔ Higher cost

• ✔ Unnecessary structural demands

• ✔ Handling difficulties

Both problems come from treating thickness as a minor detail instead of a design decision.

Best Practice for Designers

Instead of selecting thickness based on appearance alone, designers should consider:

• ✔ Panel size and span

• ✔ Support conditions

• ✔ Desired finish quality

• ✔ Installation method

• ✔ Weight limitations

Early discussion with the metal fabricator can often optimize thickness — improving results while controlling cost.

Metal thickness is not just a number on a drawing. It directly influences how metal behaves, how it looks, how it looks after installation, and how much it costs to produce.

What appears identical on paper can perform completely differently in reality. By understanding how gauge choice affects rigidity, weight, finishing, and installation, designers can avoid common pitfalls and achieve far more predictable architectural outcomes.

In architectural metal fabrication, thickness is a design decision — not a drafting detail.