One of the most important and foundational supplies used in a huge number of construction projects is the concrete masonry unit (CMU), which is a standardised construction material primarily used for load-bearing walls.

The vast majority of houses and permanent structures use concrete blocks at some point in the project, typically as the central skeleton of the building with other materials to serve as the facade such as terracotta brick or plaster.

The reasons make a lot of sense, as they are typically relatively light, have fantastic insulation properties and the most popular type of block has a hollow core that concrete can be poured down to further improve their structural stability.

However, what is not as standard is the name, as whilst the official term used in many building regulations is the concrete masonry unit, most local builders know them as breeze blocks, but across the world, they have countless other names.


The Breeze Block Mystery

Despite the giant holes in the centre, they are not known as breeze blocks because of the way the wind can pass through them, get trapped and create an air pocket that improves insulation.

In this context, breeze is the English form of the French word “braise” and refers to the ashy residue of coal that is found at the bottom of a furnace sometimes also known as bottom ash.

This is used as an aggregate material alongside cement and water to create the hard-wearing concrete that gives the blocks their compressive strength.

As bottom ash is a common industrial waste, it has become very popular as an aggregate material as it is cheap and highly plentiful, although it is not the only option.

Clinker, the irregular lumps of unburnable material left after coal is burned, can also be used to create breeze blocks as well, most commonly created as the result of producing Portland cement.

Incidentally, the most common name for breeze blocks in the United States is the cinder block, for exactly the same reason that they are known as breeze blocks.

Elsewhere, however, the common nomenclature is somewhat different. 

In the Philippines, for example, breeze blocks are known simply as hollow blocks due to the most efficient and standard design of breeze blocks with holes.

Meanwhile, in Australia, breeze blocks are known as Besser blocks, named after Jesse Benser, the inventor of the concrete block-making machine and the founder of the Besser Company that regularly sold this machine.

As it was so common as to be essentially ubiquitous in Australia, the Besser block name has endured to this day.

Whilst largely known as a construction material that is largely hidden behind other materials, breeze blocks themselves have occasionally taken the spotlight, particularly more stylised designs that became very popular in hot countries.

During the 1950s and 1960s in an age of brutalism and the celebration of concrete, they were far more at the forefront of a building’s design, but when the opinion of these large concrete structures changed dramatically, they quickly fell out of favour, only staging a comeback in the late 2010s.