Many European countries have a sound classification standard connected to the building regulations in order to specify minimum requirements. The various national standards have a lot of similarities, however the acoustic descriptors differ more than what is obvious by a quick comparison of current classification standards. The different descriptors in each country are to some extent a heritage from the past, successively adapted to the building industry in each country and their certain traditions in building technique. The descriptors and the requirements are necessarily not based on subjective experience. Furthermore, to fulfil national interests and to fit to new design trends of housing units etc, the descriptors involve small local adaptations to each country. These local adaptations are not easy to find unless the standards are read carefully. This causes problem since the building industry is not restricted to national boundaries anymore. Many companies have activity in countries adjacent to each other and in future the probability for increased activity all across Europe and also outside Europe is to be expected, unless regulations restrict this development. Combining national special rules and some severe uncertainties in the measurement and evaluation procedures of sound insulation, the situation is more critical for lightweight structures. This is partly due to the fact that the development of building systems are made in one country, the production takes place in production plants, i.e. the production and the process are fitted to local regulations and are "standardized". The standardized process is fast and dry but also needed due to lack of prediction models. And once the light weight system and the system process are established in one country it is complicated and expensive to adapt them to other countries. In this paper an overview of special national rules in some European countries and major problems connected to lightweight construction are presented.