Keith Aldis, Brick Development Association CEO, explains the importance of differentiating between clay and concrete bricks.

The UK has a long history of using bricks and mortar in housing. Almost 80 per cent of new homes built in the UK are made from brick, with the material providing a strong sense of security, beauty, and durability for the inhabitants. However, some bricks may not be what they seem.

To most of the public a brick is a brick but look a little deeper and the huge variety of colours and textures becomes clear. More than 90 per cent of bricks manufactured in the UK are made from clay, which is shaped, dried and fired in a kiln to create a hard and durable product. Firing is moving quickly towards carbon-free technology, such as hydrogen fuelling, so its potential to support claims on net-zero is fast becoming reality.

The small remaining section of the market includes bricks made from other materials, the largest of which is concrete bricks. These are made from sand and aggregates, which are mixed with pigments and cement to harden into a concrete block. Concrete bricks usually imitate the appearance of classic clay bricks, which can cause issues because some of their behaviour is quite different. It is important that designers and builders are fully aware whether they are using a clay or concrete brick for the following reasons:

Movement
The requirement for movement joints in concrete brickwork is six metres compared to 12 metres in clay brickwork. This is particulalry important for low-rise residential construction, as the use of concrete bricks will almost certainly require additional and often unsightly movement joints, where none would be required for clay.

Speed of construction
Concrete bricks tend to have lower water absorption and higher density than clay bricks. These characteristics are important because they can limit the number of bricks that can be laid in one day. Generally, the labour cost to lay bricks is the larger part of the total cost, compared to material costs. Site trials have shown that concrete bricks are around 30 per cent slower to lay, which can lead to a higher-than-expected overall cost with concrete brick.

Longevity and value
Clay brickwork has been used in the UK for thousands of years so there is a large body of evidence to show that it will last for a minimum of 150 years, with many bricks lasting considerably longer. Concrete bricks are a more recent product and there many examples from the 1980s and 90s where the pigments have leached from the brick, resulting in a dull grey concrete appearance. One of the reasons that clay brick properties retain value is that they tend to weather and age in an attractive way.

When looking in a bit more detail it becomes easy to see the differences between clay and concrete bricks. To ensure that you maximise the benefits that we associate with historic brickwork it is important to delve a bit deeper and not assume that a ‘brick is a brick’.

The BDA has produced an infographic explaining the differences.  It can be downloaded here.

Contact Details
For more information please visit the Brick Development Association website.