Mud, Glorious Mud!

There is evidence that mud bricks or compressed earth blocks were used for construction approximately 10,000 years ago in both Africa and the Middle East. The way that mud bricks have been made more recently is not too different from the ancient world.

We used a manual process where the bricks were made in a press called a CINVA-Ram, which was designed by a Chilean engineer in the 1950s – ours came from Ballarat in Victoria, thanks to eBay! The original idea behind the CINVA-ram was to provide a quick and easy way of rebuilding after earthquakes and other natural disasters. The studio includes about 500 mud bricks.

Making mud bricks is a bit like creating a recipe from the earth. The mix of ingredients includes top soil, clay, cement and lime. Quantities are a matter of trial and error but the soil and the clay are the main stars. The ingredients are blended in a cement mixer and then tipped in a barrow. The next step is to fold them together with a fork - like a cake mix, gradually adding water until the right consistency is achieved. The test for correct moisture content is when a small amount of the mixture is squeezed in your hand and it binds together – think of a biscuit mix for that part of the process!

Now the mix is ready to be ‘spooned’ into the ram. It is filled to the top, the lever on the ram is pulled down hard to compress the mix and about a minute later, the block is pushed out of the mould. It is then put on a rack to dry and is ready to lay in about four weeks.

Each brick weighs about 8kgs. and is the size of two typical house bricks. The density of each brick contributes to the thermal mass (more details on this in the next post) – the efficient heating and cooling thing. As they don’t go through a firing process, aside from the cement and lime, they are also very low in carbon content. They are laid in a bed of mortar in the same way as normal bricks and once they’ve dried, a light scree made up of clay and lime is rubbed on their surface. This is the final step before the application of a coloured lime wash finish.

We love the hand-made look of our bricks, and we use ‘Bauwerk’ lime wash paint as they have a beautiful range of colours with no added VOCs. This stands for Volotile Organic Compounds, which are carbon-based chemicals commonly found in household paint.