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Answers

How long before a terrazzo floor can be walked on?

An epoxy floor is walked on within a day: NTMA-based specifications call for a minimum of 24 hours at 25 degrees Celsius before grinding even begins. A cement-bound floor has no comparable published figure, because curing time belongs to the binder and the conditions rather than to terrazzo, so ask the installer for the time on their product.
Six terrazzo processes, drawn to one scaleEach column shows the layers of one terrazzo process. Precast and cement-bound are thick; epoxy is thin; porcelain is a fired body. Dimensions are published ranges, not our measured figures.substratePrecast20 mmsubstrateCement-based12 mmsubstrateEpoxy5 mmsubstratePoured10 mmsubstrateLiquid3 mmsubstratePorcelain9 mmSections drawn to one scale from published ranges. Our measured figures are listed separately.
The six processes drawn to one scale. Layer thicknesses are published ranges.

The figures, and where each one comes from

System Before the next trade Where the figure comes from
Epoxy minimum 24 hours at 25 C before grinding NTMA guide specification
Cement-bound ⛔ no published figure; it is a binder property —
Precast tile as soon as the fixing is set no cure on site
Liquid coating per the product per the product
What it changes Consequence
Time to grinding the programme, not the finish
Time to foot traffic whether the floor can be handed over
Time to full strength whether heavy loads are allowed

Why the processes are not interchangeable

A cement binder gains strength over weeks and a resin sets by reaction within hours, and that single difference produces every practical difference between the two floors on this site: the wet trades, the grinding sequence, the flexibility, the repairability and the renovation question. It is also why a cement floor can be ground flat against itself while an epoxy floor cannot — the cement hardens into the substrate, the epoxy sits on top as a distinct layer. The number quoted for epoxy is a floor on which nothing can happen yet, not one you may lean on: grinding at 24 hours is a machine, and foot traffic is a separate decision that belongs to the installer.

What these figures are, and what they are not

The 24-hour figure for epoxy is a minimum at 25 degrees Celsius before grinding, quoted from a published specification that states it follows the NTMA epoxy terrazzo guide. ⛔ The figures in circulation for walk-on time and for full cure come from single manufacturer product sheets rather than from a standard, and ⛔ are not reproduced here. ⛔ NO CURE TIME IS QUOTED FOR ANY CEMENT-BOUND SYSTEM, and none should be expected: it is a property of the particular binder, the mix and the ambient conditions. Ask the installer for the time on their product in your conditions.

Measured data sheets and test reports

If you are specifying this

These are the forms we actually supply for this question, with production photographs where we have them:

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