Impact sound arises when vibrations from walking, moving chairs or dropping objects are transmitted through the floor into the ceiling below and the neighbouring room. Impact sound insulation is an elastic intermediate layer that dampens these vibrations. It is laid as an underlay (sheets, boards or roll material) directly under the floating covering, or on some coverings it is already factory-laminated to the back.
The insulation often fulfils several functions at once: besides reducing sound, it evens out small unevenness in the substrate, acts as a vapour barrier (important on mineral floors against rising moisture) and, depending on the product, slightly improves thermal insulation – although with underfloor heating it is important that the underlay has a low thermal resistance so the heating is not held back.
The process: the substrate must be clean, dry and level. The impact sound insulation is butt-jointed or laid with an overlap, the joints are taped, and the covering is laid floating on top. An additional perimeter edge insulation strip along the walls is important so that the covering does not form a sound bridge to the wall.
Impact sound insulation makes sense for practically every floating floor, especially in apartment buildings and rented flats where quiet towards neighbours and legal or tenancy-law noise protection requirements play a role. With fully glued parquet, on the other hand, impact sound is solved differently.
As a material, impact sound insulation in Switzerland usually costs around CHF 5 to 20 per m² depending on quality and insulating effect; the installation is often included in the floor layer's per-m² price (guide values, no guarantee).