What are Roman numerals?
Roman numerals are the number system of the Roman Empire, in which numbers are written with seven letters. In building you meet them mainly as a date: on datestones and foundation stones, memorial tablets, sundials, bells and in wrought-iron wall anchors. They are one of the most reliable aids to dating a building.
The seven symbols
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
How to read them
The system adds from left to right: MDCLXVI is 1000 + 500 + 100 + 50 + 10 + 5 + 1 = 1666. Where a smaller symbol precedes a larger one it is subtracted: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900.
A few practical pointers for reading a façade:
- Work in blocks. Split the date into thousands, hundreds, tens and units: MDCCCLXXXVIII = M + DCCC + LXXX + VIII = 1000 + 800 + 80 + 8 = 1888.
- There is no zero and no decimal point. The system handles whole numbers only.
- Clock faces often show IIII instead of IV. That is an old clockmakers’ convention, not a mistake.
- Watch out for U and V. In old inscriptions U is often cut as V, which makes letters and numerals easy to confuse.
- The chronogram. Some inscriptions carry a motto whose enlarged capitals add up to the year of construction. If individual letters in a Latin text are cut larger or bolder, add them up.
Application in building
- Wall anchors with a date. On seventeenth- and eighteenth-century buildings the wrought-iron anchors at the beam ends are sometimes shaped as numerals. They are part of the structure; in façade repair they go back in exactly the same position, because they mark the floor beams.
- Datestones give the year of building or alteration. Always compare it with the masonry: a datestone may have been reused in a later alteration.
- Foundation stones. New buildings still regularly receive a foundation stone with a Roman date.
- Sundials and tower clocks almost always use Roman numbering.
One rule in conservation: never casually move or replace a datestone or dated anchor. On a listed building it is part of the protected fabric and often the only hard evidence of the date of construction.
Related terms
- Datestone
- Wall anchor
- Foundation stone
- Listed building
- Roman architecture
Want to know more about building terms? Visit our knowledge base at fredsdiyplans.com.