Corrugated board grades explained

Corrugated board, often referred to as corrugated cardboard or sheet board, is manufactured in a wide range of types giving different flexibility and capabilities for durability, print and more.

Manufactured from layers of flat and fluted paper, the unique combinations to form each board grade are vast. Under our expert guidance and manufacturing capabilities, we work with our customers to specify the correct board grade to deliver the strength, design capabilities and finish required.

But before we explain some of the most common board grades we use and how they support businesses, perhaps it’s important to understand how corrugated board is manufactured.

How is corrugated board manufactured?
All board grades are made using a combination of sheets of paper, referred to as liners, that are glued together with adhesive to a corrugated inner, referred to as fluting.
Corrugators process either three or five reels of paper simultaneously to produce either single wall (two liners and one fluting) or double wall (three liners and two fluting)

What difference does the outer liner of corrugated board make?

The outer liner of corrugated board plays a crucial role in determining the board’s overall performance and aesthetic appeal.

Two of the most common paper types, referred to in board grades are Kraft paper (chemically processed) which is typically is used for the outer liner of the board. This paper type is made from softwood and gives a smooth finish, ideal for printing. Test paper has a less smooth finish as it is made from hardwood or recycled paper which has shorter fibres. This is typically used for the inner liner or fluting.

What benefit does fluting add?

Fluting, the wavy layer sandwiched between the liners of corrugated board, serves several key purposes that significantly enhance the board’s functionality and performance.
This fluted liner gives strength and rigidity to the board providing cushioning and helping with stacking strength. This is why double wall is stronger than single etc. although the type of fluting, such as micro flutes in single wall can still deliver amazing strength and product protection.

By carefully selecting the flute size and combining it with appropriate liner materials, manufacturers can produce corrugated boards that meet specific performance criteria and are tailored to different applications, from heavy-duty industrial packaging to lightweight consumer goods.

Our most popular board grades and why we use them

Single Wall Board – Single wall board is composed of one layer of fluting sandwiched between two liners. It is widely used for packaging lightweight to medium-weight products. The combination of strength and flexibility makes it suitable for a diverse range of applications, including shipping boxes and retail packaging.

Double Wall Board – Double wall board consists of two layers of fluting separated by an additional liner, providing superior strength and durability. It is ideal for heavy-duty applications where extra protection is required, such as industrial packaging and large, bulky items. The dual fluted structure enhances its cushioning and load-bearing capabilities, making it highly resistant to crushing and punctures.

The most common board grades tend to be 125Kraft Test B Flute for a single walled box, and 125Kraft Test BC Flute for a double walled box. There are however dozens of different permutations of board grades available for many different customer requirements, whether that be a strengthened fluting for heavy products, or a white kraft outer layer with 3 colours of print for a presentation style appearance.

By selecting the appropriate corrugated board grade, businesses can ensure that their packaging solutions are optimised for the specific needs of their products, offering the best combination of strength, protection, and cost-efficiency.