Noise control and acoustics

The ninth entry is la couche résiliente, and the adjective inside it says almost the opposite of what an English reader now hears. In everyday English « resilient » has become a word about endurance: a resilient economy, a resilient child, somebody who takes a blow and carries on. Read the entry that way and the layer sounds like something hard-wearing, laid down to survive traffic. It is nothing of the kind. La couche résiliente works by being soft. It is a thin springy mat under la chape flottante, and its whole job is to squash under load and come back, so that the floor above never quite touches the structure below. French has kept the literal sense of the Latin resilire, to leap back, and uses la résilience in metallurgy for the energy a test piece swallows before it breaks. The trap is sharper here because the English term of art is the same word: the resilient layer in a British specification is also the soft one. Read « resilient » as springy on this page, never as tough, and the rest of the floor build-up explains itself.