What is the right cement-to-chip ratio in terrazzo?
Reference photographs. They show the material and the finish; they are not photographs of goods we made, and the colour on screen is not a colour-match.
The figures, and where each one comes from
| Ratio by volume | What it gives you |
|---|---|
| 1:1.5 | more matrix, flatter surface, chips sit deeper and stay put under load |
| 1:2.0 | the middle of the range, and where most quoted specifications land |
| 1:2.5 | more chip, more visible aggregate, less matrix to carry wear |
Why the processes are not interchangeable
The ratio is not a recipe for strength. It is a decision about how much of the finished surface is stone and how much is cement, and the two behave differently under use. At the chip-heavy end the floor looks more like terrazzo in the sense people mean, and the cement matrix has less to do. At the matrix-heavy end the surface grinds flatter and the chips are held further below the wearing layer, which matters more in a building where a trolley runs over the floor every day. The upper limit also has to sit alongside the chip rule: a 12 mm topping with 6 mm chips is at the practical ceiling of the ratio.
What these figures are, and what they are not
The 1:1.5 to 1:2.5 range is a published requirement from GB 50209-2010 clause 5.4.9. The description of what each end of the range does is engineering convention, not a quoted figure. We have not run a mix test on a panel we supplied and do not publish our own mix figures.
If you are specifying this
These are the forms we actually supply for this question, with production photographs where we have them: