Clay Brick Classes: A Guide to Brick Types and Uses

Clay bricks are one of the most essential building materials, playing a crucial role in construction projects, renovations, and even kitchen improvement endeavors. With around 2 billion bricks produced in the UK each year, understanding the different brick types and classifications can help in making informed decisions for various construction needs.

Why Are There Different Brick Types?

Not all bricks are made the same. Some bricks are cheaper to produce due to a simpler manufacturing process, while others undergo more refined processes, making them more expensive but higher in quality. To ensure the right brick is used for the right application, a grading system is introduced, particularly for burnt clay bricks. Additionally, there are unburnt clay bricks, which are different in durability and application.

Unburnt Clay Bricks

Unburnt clay bricks, also known as sun-dried bricks, do not undergo high-temperature firing. Instead, they are left under sunlight or artificial conditions that mimic sunlight to dry naturally. Due to this process, unburnt bricks lack stability and offer minimal water or fire resistance. As a result, they are mainly used for temporary structures and are prone to quicker deterioration compared to burnt clay bricks.

Burnt Clay Bricks

For higher stability and uniform appearance, modern burnt clay bricks are manufactured to standard sizes and fired at high temperatures. However, due to the vast quantity produced, the quality varies, leading to different classifications. The brick classes are essential for determining where and how these bricks should be used in construction.

What Are the Different Classes of Burnt Clay Bricks?

There are four main classes of burnt clay bricks, ranked from highest to lowest quality. The higher the class, the more durable and expensive the brick. However, choosing a lower-grade brick can help manage construction costs effectively. Below is a breakdown of the different brick classes and their applications.

Class One Bricks

As the highest-quality burnt clay bricks, class one bricks must have no visible flaws, such as stray stones, cracks, or bumps. They are characterized by:

• Sharp, straight edges and smooth surfaces.

• Uniform color throughout the brick.

• Water absorption rate of 12% - 15%.

A lower water absorption rate enhances mortar bonding, while a rate that is too high can cause excessive moisture loss, affecting the mortar's stability.

Uses of Class One Bricks:

• Facing bricks for external walls.

• Reinforcement in load-bearing structures.

• Paving for walkways and pathways.

Class Two Bricks

Class two bricks are similar to class one but may have minor surface imperfections such as slight cracks or bumps. They also have a higher water absorption rate of 16% - 20%.

Uses of Class Two Bricks:

• Hidden masonry work.

• Exterior walls, provided they are not load-bearing.

• Cost-effective alternative for non-decorative brickwork.

Class Three Bricks

Unlike class one and two, class three bricks are under-burnt, meaning they lack the same level of strength. They have a 25% water absorption rate, making them less durable.

Uses of Class Three Bricks:

• Temporary structures.

• Non-load-bearing applications.

• Short-term construction projects.

Class Four Bricks

Class four bricks are considered the lowest quality due to their irregular shape, inconsistent size, and structural weaknesses. They are often over-burnt, making them fragile and prone to cracking.

Uses of Class Four Bricks:

• Broken down for road construction.

• Used as filler in concrete flooring.

• Recycled for secondary construction purposes.

Choosing the Right Brick Type for Your Project

Understanding brick types, including burnt clay bricks and unburnt clay bricks, is crucial for selecting the appropriate building material. Whether you’re undertaking a large-scale construction project or a kitchen improvement, choosing the right class of brick can impact durability, cost, and overall efficiency. By working with the right materials, you can ensure a long-lasting and stable structure while keeping your budget in check.