A composite construction element (1) is described, comprising: a) at least one elongated body (2) made of expanded plastic material provided with opposite faces (2a, 2b); b) at least one reinforcing section bar (7, 8) longitudinally extending in the elongated body (2) and having a first lateral portion (7b, 8b) protruding from a first face (2a) of the elongated body (2); wherein the first lateral portion (7b, 8b) of the reinforcing section bar (7, 8) is provided with a face (9, 10) extending substantially parallel to the first face (2a) of the elongated body (2) made of expanded plastic material at predetermined distance therefrom. Advantageously, the construction element (1) exhibits improved self-supporting characteristics and improved supporting characteristics of covering elements externally associated to the construction element itself.