Opus is Latin for work or built work. In architecture it is the collective term for Roman walling and flooring techniques, each with a qualifier describing how the material was stacked or laid: opus incertum, opus reticulatum, opus spicatum and so on.
The Romans built many walls as cored construction: two outer faces of stone with a core of opus caementicium, a mortar filled with stone rubble. The opus name usually refers to the appearance and build-up of that outer face.
The main opus types
| Name | Characteristic |
|---|---|
| Opus quadratum | Large, uniform rectangular blocks in regular courses |
| Opus isodomum | Courses of equal height, block length may vary |
| Opus incertum | Irregularly shaped rubble set randomly in mortar |
| Opus reticulatum | Square stones set diagonally; the appearance of a net |
| Opus latericium | Cored walling with brick as the outer face |
| Opus mixtum | Combination of stone types and bonds, often brick bands within stone |
| Opus vittatum | Banded work: courses of regular small blocks |
| Opus listatum | Alternating layers of large stone and thin brick courses in concrete |
| Opus africanum | Long vertical and horizontal blocks framing panels, filled with smaller material |
| Opus craticium | Timber framing with infill — the Roman half-timbered wall |
| Opus spicatum | Herringbone bond, much used in floors and paving |
| Opus signinum | Lime mortar with crushed tile; waterproof, used in cisterns and baths |
| Opus tesselatum | Mosaic of small regular cubes (tesserae) |
| Opus barbaricum | Floor of pebbles or small stones |
Why it still matters
Several of these techniques never disappeared:
- Opus spicatum is the herringbone bond you still see daily in block paving and herringbone parquet. The interlocking diagonals distribute point loads well, which is why it remains popular for trafficked surfaces.
- Opus signinum is the ancestor of waterproof cement mortar; the principle — lime with fired clay grit as a pozzolan — is still technically sound.
- Opus incertum reappears in modern rubble walls and dry-stone garden walling.
A common confusion
“Opus” describes the technique, not the period. A nineteenth-century garden wall laid in herringbone is, technically, opus spicatum, even though no Roman was involved. And a modern stretcher bond is not an opus — it is simply a bond pattern.
Related terms
- Bond pattern
- English cross bond
- Brick
- Listed building
Learn more about building terms in our knowledge base at fredsdiyplans.com.