Floating floors: definition and acoustic principles

What is a floating floor?

A floating floor is a flooring system in which the finish layer—the screed and flooring—is physically separated from the load-bearing structure by a flexible layer. There is no rigid contact between the two, neither at the base nor along the edges.

The term describes an acoustic principle rather than a specific material. It is not the screed that provides sound insulation, but the discontinuity. A ten-centimeter screed laid directly on the slab will transmit impact noise more effectively than a six-centimeter screed that is properly decoupled.

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The mass-spring-mass principle

The system functions through three successive elements:

• A first mass, the screed and its finish
• A spring, the resilient underlay, which absorbs and dissipates vibrational energy
• A second mass, the load-bearing slab

When an impact occurs on the surface, the energy must pass through the spring to reach the structure. A large portion is dissipated as heat instead of continuing through. This is what prevents footsteps on the first floor from echoing on the ground floor.

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Why edge isolation is the deciding factor

This is where most failures occur. If the screed touches a wall, threshold, pipe, or column, it creates a sound bridge: vibrations bypass the spring and travel directly into the structure.

The edge strip must therefore be continuous around the entire perimeter, extend above the finished floor level, and only be trimmed after the flooring is installed. There are no half-measures here: a floating floor either works or it doesn't. A single point of contact is enough to compromise it.

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What it treats and what it doesn't

A floating floor treats impact noise: footsteps, heels, dropped objects, and moving furniture. This is its primary function, and it is highly effective at it.

It is much less effective against airborne noise, such as voices, music, or television, which travel through the air and also propagate through walls and ceilings. Confusing the two leads to investing in the wrong solution and concluding that acoustic insulation is useless.

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The distinction regarding floating screeds

The two terms are often used interchangeably. A floating screed refers to the element itself—the screed—decoupled from its base. A floating floor refers to the complete system of which it is a part.

A floating screed laid on purely thermal insulation remains a floating screed, but it does not necessarily constitute a high-performance acoustic floating floor: the intermediate layer must be chosen for its resilience, not just its thermal resistance. This is the principle behind our acoustic solutions, detailed in our article onacoustic insulation under screeds.