Is terrazzo cold underfoot, and can it be heated?

A cement-bound floor is cold, because it is a dense slab laid on the structure with nothing insulating between it and the slab. Underfloor heating changes that: a thin resin terrazzo conducts heat better than a thick cement one, because there is less mass between the pipe and the room. The heat source is the fix, not the finish.

The six processes drawn to one scale. Layer thicknesses are published ranges.

The figures, and where each one comes from

System	Mass in the floor	On underfloor heating
Epoxy, 3/8 in	the least	the best conductor of the group
Monolithic cement, 1/2 in	more	workable
Sand cushion, 3 in	the most	works, but slow to respond
Precast tile	the tile only	depends on what is under it

Why the processes are not interchangeable

Two things are going on and they are separate. The cold feel of any hard floor is thermal mass: it draws heat out of the room faster than a resilient floor does, and a thick cement floor has more mass than a thin resin one. The second is response time, which is worse in a sand-cushion floor because the same mass has to be heated before the surface changes. Both point the same way — where a heated floor is wanted and the structure allows it, the thinnest terrazzo system that will do the job is the right one, and that is usually epoxy rather than the thickest.

What these figures are, and what they are not

The build-ups are from the NTMA Terrazzo Systems Reference Guide. ⛔ We give no thermal figure: we could not trace a conductivity or response-time number to a standard, and the percentages in circulation come from vendor copy, so none is reproduced here. ⛔ Whether a floor can be heated is a question for the heating design, not for the floor supplier.

Measured data sheets and test reports

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