What is a radial brick?
A radial brick is a fired brick shaped like a trapezium, often with a curved face, so that it wedges neatly into curved masonry. The outer face is usually convex and the back is flat or tapered. Laid side by side, radial bricks form a true circle with even joints, which ordinary rectangular bricks cannot do at small radii.
Why the wedge shape matters
In a circular wall the outer circumference is longer than the inner one. That difference has to go somewhere. With ordinary bricks it ends up in the perpend joint, which opens wide on the outside and closes up on the inside. On a tight radius the result looks poor and is structurally weak, because the bricks bear on only part of their end face. The alternative is cutting standard bricks to shape, which is slow and exposes the soft interior of the brick to the weather.
How they are made
Radial bricks are extruded through a die. Every format and every radius needs its own die, so they are made to order: more expensive than standard bricks, with longer lead times and a narrower choice of colours.
| Feature | Practical consequence |
|---|---|
| One brick size suits one internal radius | On a different radius the joint thickness no longer works out |
| Dedicated die per size | Made to order, rarely available from stock |
| Curved exposed face | Clean curved brickwork with no cut edges |
Order on the internal radius of the structure, not on quantity alone.
Where they are used
- Round brick chimneys of varying diameters, the classic radial brick chimney.
- Wells and silos, where the wall keeps the same radius over its full height.
- Arches and tapering structures, where the brick carries the curve itself.
- Columns and round piers in fair-faced brickwork.
Before ordering, set out the work on paper. Internal radius, wall thickness and intended joint thickness together decide which brick format fits.
Related terms
- Special shaped brick
- Wedge brick
- Setting out
- Chimney
- Arch
- Joint thickness
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.