"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."
Commission Recommendation 2003/887/EC

Nationally Determined Parameters

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:

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. []