Tony M May 11, 2021:

@ Asker In a text about carpeting, 'underlay' is bound to recur! Fabric-backed carpet is traditionally laid on a separate 'mat' called 'underlay', usually a cheap, low-grade felt-like fibre.
Some carpets have a cheaper but less durable foam backing bonded onto them, which as your article suggests, makes for faster laying, as only one item has to be cut to size.
What exactly is special here is not clear; it seems that possibly this is mid-way between the two: a more durable felt-like backing, perhaps made of several layers, but all together bpnded to the structure of the carpet.

If you can find out more detail of the actual composition and structure used, you might be able to find a more apposite term in FR.
What is different about your product is not clear

Séverine torralba (asker) May 10, 2021:

Underlays There is definitely something about layers as the term "underlays" is recurrent in the text. An other paragraph: "The more traditional textile backing can be used with separate underlay and grippers, while the lightweight and flexible integrated felt backing is a more sustainable option, containing 80% regenerated polyester that allows for more speedy fitting."

Tony M May 10, 2021:

@ Asker I think in this sort of case we'd be more likely to talk about something like 'multiplex' or 'multicouche' etc., wouldn't we? I don't believe either 'stratifié, nor still less 'laminé', would work for an underfelt backing.