Member States should lay down the parameters usable in their territory, hereinafter 'the nationally determined parameters'.
Member States should use the recommended values provided by the Eurocodes when nationally determined parameters have been identified in the Eurocodes. They should diverge from those recommended values only where geographical, geological or climatic conditions or specific levels of protection make that necessary.
EN Eurocodes recognise the responsibility of regulatory authorities in each Member State and have safeguarded their right to determine values related to regulatory safety matters at a national level where these continue to vary from State to State.
EN Eurocodes provide for National Choices full sets of recommended values, classes, symbols and alternative methods to be used as Nationally Determined Parameters (NDPs).
When Member States lay down their NDPs, they should:
- choose from the classes included in the EN Eurocodes, or
- use the recommended value, or choose a value within the recommended range of values, for a symbol where the EN Eurocodes make a recommendation, or
- when alternative methods are given, use the recommended method, where the EN Eurocodes make a recommendation;
- take into account the need for coherence of the NDPs laid down for the different EN Eurocodes and the various parts thereof.
When the EN Eurocodes are used for the design of construction works, or parts thereof, the NDPs of the Member State on whose territory the works are located shall be applied.
Member States are encouraged to minimize the number of cases where recommendations for a value or method are not adopted for their nationally determined parameters. By choosing the same values and methods, the Member States will enhance the benefits of the use of the EN Eurocodes.
The European Commission urged Member States to reduce divergence from the recommended values provided by the EN Eurocodes and promote further harmonisation of the standards.
The National choice
The National Annex contains information on the Nationally Determined Parameters, to be used for the design of buildings and other civil engineering works to be constructed in the country concerned, i.e.:
- values and/or classes where alternatives are given in the EN Eurocode;
- values to be used where a symbol only is given in the EN Eurocode;
- country specific data (geographical, climatic, etc) e.g. snow map;
- procedure to be used where alternative procedures are given in the EN Eurocode.
It may also contain:
- decisions on the application of informative annexes;
- references to non contradictory complementary information to assist the user to apply the EN Eurocode.