The subfloor must comply with the existing requirements for evenness (± 2 mm per 2 m). The subfloor must not slope. When installed on leveled subfloors including a drain, the underside of the edges of the drain itself must be filled with non-curing silicone.The underside of the wall bases which are in contact with the surface of the floorboard must be added non-curing silicone in order to prevent water from leaking under the installed flooring. This also applies for other mouldings used for transmissions or endings.