EC marking can only be given to construction products complying with national legislation harmonized with European norms, that meet European technical approval regulations or, in their absence, that comply with national technical specifications that are in accordance with minimum essential requisites.

Essential technical specifications are defined by national norms resulting from transposition of a harmonized norm, i.e., a technical specification elaborated by the European Committee for Standardization (CEN), which, in the case of Clay Roof Tiles and roofing Accessories, is NP EN 1304. 

Thus, all materials with the CE marking meet the essential requisites as defined by the Directive on Construction Products. 

As for the certification of conformity, it is up to the makers to certify, by their own means or by a duly recognised certification organism that products comply with the requisites of a technical specification in accordance with the certification of conformity procedures as described by the Directive on Construction Products.