Brush the surface and remove every remnant of waste from where the underlay will be installed in order to obtain an even and smoothed-out surface. The surface shall correspond to the following flatness criterias: ≥7 mm under a 2 m plank and it has to be ≤ 2 mm under a 20 cm plank. In certain cases, a levellling screed must be applied over the ducts to obtain an even surface.
Installation of the underlay
Place the insulFib 3+ in a single or double-layer* (crossed) while making sure that the white felt faces the ground. The insulFib 3+ strips must be laid side by side, with no space in-between. Remove the protective film from the flat overlap made of spunbond non-woven fabric (±6 cm) and make sure to fully cover the parallel insuliFib 3+ strip. Pull-up more or less 15 cm of insulFib 3+ along the walls or use a edge strip made of PE-foam (Lfoam). The vertical ducts have to be insulated (or covered) either with flexible sleeves or with handmade strips of insulFib 3+.
*see local regulations
Making of the screed
Immediately after placing the underlay, pour a reinforced screed (minimum thickness: 5 cm on a single layer of
insulFib 3+ and 6 cm in case of a double layer). In case of underfloor heating, the thermal panels must be laid
upon the underlay. When the screed and the floor covering have been successfully placed, cut the remaining insulFib 3+
or the remaining PE-foam circumferential strip. The plinth has to be placed slightly higher than the floor covering in order
to avoid lateral acoustic transmissions. The last step would be to create a flexible joint under the plinth.
The screed and the slab made of hydraulic binders have to comply with the local regulation.