A composition comprising cellulose ether, a superplasticizer and defoamer suitable for use as an additive in extruding inorganic compositions is disclosed. The inventive composition functions as a water retention agent, plasticizer and lubricant in the extrusion of inorganic compositions. The use of the inventive composition in the extrusion of building materials leads to improved processing properties, to a higher surface quality and product properties of the extruded article.