Processing
Why two terrazzo floors with the same surface can differ by half the price
The surface is the last thing that happened. A floor is priced before anyone sees it, and the difference between two quotes is usually decided by three things that were settled before the first chip was ground.
A sample tells you what a floor will look like. It tells you nothing about what the floor is made of, and on this material the two are not the same question.
The visible part is the last part
Terrazzo is made by grinding. The aggregate is graded through the binder, so the surface does not exist until a grinder has cut through the matrix to reach the stone — and because the chips sit at different depths, one pass would leave high stone and low cement side by side. Each pass therefore uses a finer grit and takes a little less.
Everything before that pass decides the cost, and none of it is visible in a sample:
- how much build-up sits under the topping, and who made it
- how large the aggregate is, which is a function of the topping thickness
- how many passes the floor has to take before it is flat
Build-up is the largest single difference
The published systems differ mostly in what is underneath the topping, not in the topping itself. A cement-bound sand-cushion assembly is 3 inches in total with a half-inch topping; a bonded assembly is 2-1/4 inches; a monolithic one is the half-inch topping alone; an epoxy floor is 3/8 inch. In weight the same four run from 25-30 lbs per square foot down to 3-4.
Read that again. The heaviest system is roughly eight times the weight of the lightest one, and the topping on the two heaviest is the same half inch. The difference is entirely below the line a reader can see.
Aggregate size is arithmetic, not a choice
JC/T 507-2022 clause 5.3 sets the largest chip at two thirds of the topping thickness. At a 12 mm topping that is 8 mm of aggregate. At 8 mm it is about 5.3 mm. A request for large aggregate in a thin topping is not a preference that a supplier can satisfy; it is a contradiction.
This is the constraint that decides a thin floor, and it is written into the Chinese codes. Most material published in English does not give it.
Renovation removes the heaviest option from the start
The sand-cushion assembly cannot go into a renovation, because its elevation cannot be added to an existing floor. And on an older slab, cracks in the substrate telegraph straight through a monolithic or bonded cement floor. An epoxy floor tolerates both, because it is thin and can carry a crack-resistant membrane — which no cement system accepts.
So on a renovation the choice is often made before the price is quoted.
What to ask for
Ask three questions, in this order. What is the assembly under the topping, in millimetres. How many grinding passes, and what flatness has to be achieved at each. Where does the aggregate come from and what is its maximum size. A supplier who answers those three precisely is describing a floor; one who answers “we supply terrazzo” is describing a catalogue.
What we do not say here: no price, no lead time, and no test result for our own material. We hold none of the three, and a number without a document behind it is the easiest thing in this trade to invent.
Filed under Processing