The project owner of a new building shall ensure that the soundproofing of the external building elements and partitions of rooms sensitive to noise, and of the stairs and building facilities complies with recognised codes of building practice. These are in particular, for noise from civil aerodromes that are used by heavy aircraft, the stricter requirements, and for noise from other stationary installations, the minimum requirements, of SIA Standard No 181 of the Swiss Society of Engineers and Architects.39
If the ambient limit values are exceeded but the requirements of Article paragraph 22 for granting a building permit are met, the enforcement authorities shall impose stricter requirements for the soundproofing of the external building elements appropriately. The costs associated with these stricter requirements shall generally be considered reasonable if they do not exceed one per cent of the building costs.40
The requirements also apply to the external building elements, partitions, stairways and building facilities that are converted, replaced or newly installed. On request, the enforcement authorities grant relief if compliance with the requirements would involve unreasonable cost.