Are cork panel sizes random or carefully designed?

 

At first, it might appear that larger cork boards—as with many other products—automatically mean higher quality: fewer seams, faster installation, and a more striking appearance. In truth, however, the board’s size has little to do with aesthetics or a manufacturer’s whim. It is dictated by specific technological and physical constraints that stem from the natural characteristics of the material and how it is processed.

In this article, we’ll explore what causes these limitations, how cork boards are made, and why certain dimensions have become the accepted industry standard.

 

Table of Contents
1. Introduction
2. Cork boards
3. Expanded natural cork
4. Decorative cork panels
5. Summary
6. FAQ

 

Cork boards

Where natural cork originates

The key raw material comes from the bark of the cork oak tree (Quercus suber), which grows mainly in Portugal, Spain, and southern France. The trunk itself is never cut down—only the bark is removed, making natural cork production both renewable and environmentally sustainable. After harvesting, the bark is seasoned, dried, and ground into granules of various sizes.

These granules are used to produce agglomerated natural cork—a material made by fusing cork particles under heat and pressure, with the help of either natural or synthetic binders depending on the type. The process used to make expanded natural cork differs in several important ways, which we’ll explain later in the article.

Agglomeration and the creation of blocks

Cork granules are poured into molds and pressed at high temperatures. This step, known as agglomeration, produces production blocks—large, compact cork masses with precisely defined measurements. These blocks determine the maximum possible dimensions of the boards that are later cut from them.

The block size depends on the design of the mold and the capacity of the machinery—especially the presses, which must ensure consistent temperature and pressure across the entire volume. If the mold is too large, bonding becomes uneven, resulting in deformations, air pockets, or delamination in the finished board.

Production blocks and how they define board size

A production block can be compared to a “loaf of cork bread”: it has a specific volume determined by the mold size and press performance. Each cork board is essentially a “slice” cut from that loaf. This means that the maximum size of a board is directly dependent on the mold dimensions, which are restricted by both equipment capabilities and the physics of the heating process.

If the mold were made any larger, the core wouldn’t heat evenly, preventing the material from reaching the desired density—the center could end up soft, porous, or brittle.

Why the standard board size is 640 × 940 mm

The standard size for agglomerated natural cork boards is 640 × 940 mm. This dimension directly reflects the size of the production blocks created in molds with specific depth and width parameters.
This size wasn’t chosen at random—it offers an ideal balance between production efficiency, dimensional stability, and ease of transport and installation.

Larger boards come with higher risks, such as:

• warping during the cooling process,

• uneven compression,

• cracking during cutting or handling.

That’s why the 640 × 940 mm format became the industry benchmark—not due to an arbitrary decision but because current technology cannot produce larger sizes without sacrificing quality.

What happens when we try to “scale up”

Efforts to manufacture larger boards almost always fail—the material tends to bend, crack, or lose dimensional stability.
Often, the board appears stable right after being removed from the mold, but within a few days—as temperature and humidity even out—deformations and fine cracks begin to appear.

For this reason, manufacturers adhere to dimensions that ensure the highest quality and consistency. When it comes to cork, “bigger” doesn’t always mean “better.”

 

Expanded natural cork

Different technology, different limitations

Expanded natural cork differs significantly from conventional agglomerated cork. Though both are produced from cork granules, their manufacturing processes are fundamentally distinct.
In the case of expanded natural cork, the granules are not joined with any binders but fused entirely through heat and steam. The high temperature activates the cork’s natural resin—suberin—which serves as a natural adhesive, bonding the particles into a compact structure.

This process is clean and environmentally friendly—yet far more complex to regulate. Without synthetic binders, any fluctuation in temperature, density, or steam flow can lead to internal stresses, which limit the maximum size of the blocks and boards.

Differences in density, expansion, and cooling

During expansion, cork increases its volume by several dozen percent due to the gases trapped inside its cellular structure. In practice, this means that temperature and pressure within a large block are distributed unevenly.

The center heats up more slowly, while the outer layers heat faster, creating variations in density and hardness. As the block begins to cool, these differences cause it to “move”:

• the core may stay slightly foamy and soft,

• while the edges harden and shrink more quickly.

As a consequence, internal stresses develop, causing the board to fracture or bulge either immediately after demolding or later during the drying phase.

This is why the manufacturing method for expanded natural cork can’t accommodate large-format blocks—the larger the mold, the greater the risk of inconsistency. In turn, this constrains the final board dimensions.

Why oversized expanded natural cork boards crack or distort

In theory, it’s possible to attempt a board larger than 500 × 1000 mm, but in practice it proves technologically inefficient and too risky in terms of quality.
During the cooling phase, large expanded natural cork boards:

• crack along paths of highest stress,

• warp due to uneven contraction,

• lose planarity, making them unsuitable for covering large surfaces.

For this reason, the 500 × 1000 mm size has become a natural upper limit—it’s the format at which thermal conditions remain controllable, density stays uniform, and dimensional stability is maintained.

As a result, expanded natural cork boards preserve their key advantages: excellent thermal and acoustic insulation, inherent elasticity, and full resistance to biological degradation—without sacrificing quality.

 

Decorative natural cork panels

Practical considerations: installation, weight, stability

For wall applications of natural cork, practical aspects are just as important as technology. The 300 × 600 mm board format isn’t arbitrary—it’s the outcome of extensive installation trials and real-world feedback.
This size is lightweight, manageable, and simple to install even for one person. It can be trimmed and positioned accurately without risking damage to the edges.

While larger boards may cover more surface per piece, they are harder to control during adhesion: the additional weight makes precise leveling more difficult, and even minor inconsistencies in pressure or adhesive application can lead to undulation and lifted corners.

Oversized formats = challenges during application and bonding

When mounting wall natural cork, aesthetics matter—but the priority is a reliable bond with the substrate. Natural cork is flexible and responds to changes in temperature and humidity, so adhesive forces must be distributed evenly.

With larger boards, achieving uniform adhesion across the entire surface is more difficult—small variations in adhesive thickness can cause:

• air pockets,

• lifting at the corners,

• stresses that eventually cause the panel to detach.

Larger pieces are also more susceptible to deformation under their own weight. So, although they may look appealing initially, their long-term durability and installation reliability are noticeably poorer.

Ergonomics and aesthetics—why smaller boards often look better

The 300 × 600 mm format is not only practical but also visually versatile. It enables regular, rhythmic layouts and lets you scale the pattern to a room’s proportions. With smaller modules, joints remain discreet yet visible—emphasizing the natural character and texture of the material.

Very large boards upset visual balance: they can appear bulky on the wall, and their edges draw attention instead of harmonizing with the texture of natural cork. Additionally, any minor unevenness in the wall becomes more apparent because larger boards don’t “conform” to the substrate as effectively as smaller ones.

This is why the 300 × 600 mm format is widely regarded as an optimal middle ground—balancing ease of installation, durability, dimensional stability, and the final appearance.
It’s not a coincidence but the result of experience and practice showing that with natural cork—as with many natural materials—smaller often proves better.

 

Summary

At first glance, cork board size may seem like a purely practical or stylistic choice. In fact, every dimension reflects clear technological reasoning and production know-how that define what’s both viable and durable.

Board dimensions aren’t arbitrary, nor are they chosen at random by manufacturers. They result from:

• the inherent nature of the raw material, with its cellular structure and thermal response,

• technological limits such as mold dimensions, press performance, and control of the fusing process,

• practical concerns involving installation, weight, stability, and the final look.

That’s why, despite their initial appeal, larger boards typically create more complications than advantages.
Natural cork is a “living” material that merits respect for its boundaries—and knowing why its dimensions are what they are is a strong sign of technical and quality awareness for both makers and users.

 

FAQ

1. Why can’t I get a natural cork board in any size I choose?

Because board size is tightly linked to production methods and the properties of natural cork. The blocks from which boards are cut have set dimensions based on press capacity, mold size, and the fusing process. Increasing the format would result in deformation and reduced quality.

2. Why are 640 × 940 mm and 500 × 1000 mm considered standard?

These measurements come from the size of production blocks. For agglomerated natural cork, 640 × 940 mm is the optimal format produced by standard molds. For expanded natural cork, the binder-free fusing method dictates different block limits—hence the 500 × 1000 mm maximum.

3. Do smaller boards mean more seams on the wall?

Yes, but that isn’t necessarily negative. With natural cork, those seams become part of the design—subtle and consistent with the material’s texture.