Opus spicatum

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Opus spicatum, meaning “spiked work,” is a way of building with bricks, tiles, or cut stone laid in a herringbone pattern. It was mainly decorative in Roman and medieval times, often used as a pavement and sometimes as wall infill, such as at the base of the causeway to Tamworth Castle.

Because the pieces are placed on the diagonal, the pattern can be weak if there are no straight horizontal or vertical elements; the angled pieces can push the pattern apart under compression. Still, the herringbone arrangement creates opposing shear planes and more surface area, which can help mortar bond and make the construction sounder. It was also used to make firebacks in stone hearths, as acidic flue gases wear mortar less quickly with a finely set herringbone.

Opus spicatum was widely used by Romans, Byzantines, and in Romanesque buildings. In Byzantium it appeared on walls in Asia Minor and was used decoratively in churches to add variety to wall surfaces. Sometimes the diagonal rows are reversed one above the other.

Notable examples include Usk Castle. Filippo Brunelleschi used herringbone in the dome of the Cathedral of Florence. In France, examples exist in the churches at Querqueville (Normandy) and St Christophe at Suèvres (10th century). In England, herringbone masonry appears in the walls of Guildford, Colchester, and Tamworth castles. It also appeared in Gothic Revival architecture.