Red bricks are a widely used building material, known for their warm colors and natural appearance. They require no ongoing maintenance once built and have been used in construction for thousands of years. This guide will explore the history, manufacturing, quality, and best uses of red bricks, especially in the context of Bali’s construction landscape.

History and Global Use

Bricks have a long and rich history. Some believe that Arabs invented bricks, and the Middle East has a long history of using them. Ancient Greeks and Romans also used bricks in their buildings. In Britain, bricks are known for their strength and have been used for centuries in structural applications, including large buildings, churches, factories, and even sewer systems. The ground stability in Britain allows bricks to be used without reinforcement. Accrington bricks from Lancashire, are known as the hardest and densest in the world, even being used in the foundations of the Empire State Building.

In Australia, bricks are more often used for aesthetics rather than structural support. Most houses use a “brick veneer” method, where a lightweight wooden frame is lined with plasterboard and covered by an outer brick layer.

The Manufacturing Process

The strength of a brick is determined by the clay mixture, compaction, and firing process. Typically, manufactured bricks contain 50-60% silica (sand), 20-30% alumina (clay), 2-5% lime, up to 7% iron oxide, and some magnesia. Local materials are often used, with water added to create a soft mud, which is then formed into blocks and either sun-dried or fired in a kiln. Fine-grained clays produce denser and stronger bricks. Bricks may be pressed to remove air pockets before firing to increase their hardness.

Firing requires temperatures between 900°C and 1,000°C for the silica to fuse, providing strength. The color of the bricks depends on the chemical and mineral content of the clay and the firing temperature. Iron gives bricks their red color, while lime results in yellow bricks. Cooler temperatures produce red bricks, with hotter temperatures resulting in browns and greys. The shape of the brick, the strength of the mortar, and the brick placement affect the overall wall strength. A frog, an indent on the brick, helps with “keying” bricks together. Mortar should be a mix of four parts sand to one part cement.

Brick Dimensions and Structural Integrity

The size of bricks is important, balancing ease of handling with minimizing construction effort. A standard brick is approximately 9″ long, 4½” wide, and 3″ thick, including mortar. This ratio of 6:3:2 allows for varied placement combinations in structures. Traditional Balinese bricks are often thinner, around 2″ thick. In Indonesia, due to the risk of earthquakes, bricks must be used with concrete columns and beams for structural support. The 2006 Yogya earthquake caused the collapse of around half a million houses due to single-skin brick walls built with weak brick and no reinforced concrete support.

Selecting High-Quality Bricks

It’s essential to check the quality of bricks before they are used, as it’s difficult to assess their strength once they are built into a wall. Ensure your source provides strong bricks of consistent quality. The clay should be fine-grained with the right mix of clay and sand, dense, without air gaps, and fired at the correct temperature. Be cautious with rustic-looking bricks, as pressed bricks are stronger. In Bali, bricks are produced in various regions, and their quality varies depending on the clay and the skill of the brick makers. Some producers use “fillers” like rice chaff, which is not ideal.

In small operations, bricks are stacked in wood-fired kilns, with the bricks at the bottom being harder due to higher temperatures. Bricks from the middle are general-purpose, and those at the top are softer, often used in traditional buildings. The best Balinese bricks come from Tabanan and Tulikup, where numerous family-run kilns are located. However, quality varies according to the skills of the people making them.

Testing Brick Quality

Several tests can help you assess the quality of bricks:

• Sound Test: Lightly bang bricks together. Well-fired bricks will produce a ringing sound, while poorly fired ones will sound like a dull thud.
• Drop Test: Drop a brick. A hard brick will break cleanly, while a poorly fired brick will crumble and fall apart.
• Concrete Hardness Test Hammer: While not designed for bricks, this test can also be effective.

Conclusion

Understanding the properties of bricks is critical, especially when building in areas prone to earthquakes like Bali. Ensure that your building has reinforced concrete to prevent collapse and save lives.