What is a brick extruder?
A brick extruder is a machine that forces prepared clay through a shaped die to form a continuous column of constant cross-section, which is then cut into individual bricks by a frame of tensioned wires. The bricks it produces are known as wire cut bricks or extruded bricks. The underlying process is extrusion; the Dutch call the machine a strengpers.
The clay is first mixed with water in a pug mill: roughly 10 to 15% water for stiff extrusion or 20 to 25% for soft extrusion. In a de-airing extruder the clay passes through a vacuum chamber to remove air before an auger compresses it and drives it towards the tapering press head. There it is pushed at high pressure through the die, which sets the width and depth of the column. Cores fitted in the die create the holes of perforated bricks, and a profiled die makes shaped bricks. The column is then sliced to brick size, dried and fired. Most structural bricks are made this way, because the method produces hard, dense bricks economically.
Recognising it
A wire cut brick has four smooth faces, formed as the clay slides through the die, and two rougher cut faces, which may show drag marks from the wire. It is very regular in shape, unlike a hand-moulded brick. The column can be textured with rollers or sand-faced before cutting.
In practice
- Agree the face side. Smooth and cut faces look different. Ask the manufacturer which faces are intended to be seen and lay the bricks consistently.
- Use the accuracy. The regular shape makes neat, narrow joints and crisp brickwork easier.
- Check frost resistance. For facades and freestanding walls, confirm the declared frost resistance, especially when reusing old bricks.
- Do not mix casually with hand-moulded bricks. Wire cut and hand-moulded bricks look very different, and mixing them in one wall rarely looks intentional.
Common mistake: laying bricks at random, so smooth and rough faces appear side by side in the elevation. The result looks patchy; agree the face side with the bricklayer before work starts.
Related terms
- Extrusion
- Brick manufacturing
- Hand-moulded brick
- Perforated brick
- Moulded brick
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