How do you make a polished terrazzo floor safe?

Specify the finish rather than treating the floor afterwards. In the United States the number to ask for is a wet DCOF of 0.42 or higher, which is the accepted threshold under ANSI A326.3 for a level interior floor that will be walked on wet. A honed or matte terrazzo is not slippery; a polished one is.

Reference photograph of a terrazzo surface, s61. Not a photograph of our goods. — A curved stair edge in mixed aggregate

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

Use category under ANSI A326.3	Minimum wet DCOF	Where
Interior, dry (ID)	0.42	rooms with no water source
Interior, wet (IW)	0.42	bathrooms, kitchens, entrances, public restrooms
Interior, wet plus (IW+)	0.50	public showers, locker rooms, pool surrounds
Exterior, wet (EW)	0.55	maintained outdoor areas
Oils and greases (O/G)	0.55	kitchens and greasy spaces

Why the processes are not interchangeable

Terrazzo does not slip because of terrazzo; it slips because of the polish, and a polish is a mirror whatever the stone under it. That makes the decision a specification made at the finish stage and very hard to reverse — a floor ground to a high polish and then found slippery in the wet has two routes back and both involve taking it down. Three things have to travel with the number or it will be misused. The instrument is the BOT-3000E tribometer specifically, not a pendulum and not a drag sled. ANSI A326.3 states plainly that it makes no claim of correlation to actual footwear or to human walking, so 0.42 is a material property and not a prediction about a person in shoes. And the standard sets no value for a shower floor at all — that category is left to a manufacturer declaration.

What these figures are, and what they are not

The categories and thresholds are ANSI A326.3, read from three independent sources that agree. ⛔ Two cautions travel with them and are repeated above: A326.3 specifies the BOT-3000E instrument, and it states no correlation to footwear or walking. ⛔ ASTM C1028, the older static method, was withdrawn — a report that still cites it is quoting a retired method. EN 13748-1 includes an unpolished slip resistance method and its scope was read, but ⛔ we have not obtained the standard and no European value appears here. ⛔ We have not tested a wet surface of ours and hold no DCOF result.

Measured data sheets and test reports

If you are specifying this

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