Process for manufacturing a plastic composite profile, of any cross-section, having a foamed core of density lower than 400 Kg/m 3 surrounded by an outer layer of density higher than 500 Kg/m 3, said process comprising the steps of: a) plasticizing a first polymer composition in a first extruder, said first polymer composition comprising a styrenic polymer composition and a first foaming agent, b) plasticizing a second polymer composition in a second extruder, said second polymer composition comprising a styrenic polymer composition, and optionally a second foaming agent, c) feeding the plasticized first and second polymer composition to a coextrusion die so as to form a plastic composite having a core formed of said first composition and an outer layer made of said second polymer composition surrounding said core, d) converting said plastic composite into a shaped plastic extrudate by passing said plastic composite through an extrusion head having a die-lip of cross-sectional area and shape adequate for achieving the cross-sectional area and shape of a calibration unit at the end of step (f), e) contacting said outer layer of said plastic composite with a lubricant downstream from said feeding of said second polymer composition and either before or during conversion step (d), f) allowing the core and optionally the outer layer of said shaped plastic extrudate to freely foam over a distance adequate for the cross-sectional area and shape of said shaped plastic extrudate to reach the cross-sectional area and shape of said calibration unit within a tolerance T of the point of entry of said shaped plastic extrudate in said calibration unit, wherein T is ±0.2 cm, and g) passing the foamed shaped plastic extrudate obtained at the end of step (f) in said calibration unit, thereby providing said plastic composite profile, wherein, in the cross-section of the plastic composite profile, said outer layer surrounds completely said core of said plastic composite profile. a) plasticizing a first polymer composition in a first extruder, said first polymer composition comprising a styrenic polymer composition and a first foaming agent, b) plasticizing a second polymer composition in a second extruder, said second polymer composition comprising a styrenic polymer composition, and optionally a second foaming agent, c) feeding the plasticized first and second polymer composition to a coextrusion die so as to form a plastic composite having a core formed of said first composition and an outer layer made of said second polymer composition surrounding said core, d) converting said plastic composite into a shaped plastic extrudate by passing said plastic composite through an extrusion head having a die-lip of cross-sectional area and shape adequate for achieving the cross-sectional area and shape of a calibration unit at the end of step (f), e) contacting said outer layer of said plastic composite with a lubricant downstream from said feeding of said second polymer composition and either before or during conversion step (d), f) allowing the core and optionally the outer layer of said shaped plastic extrudate to freely foam over a distance adequate for the cross-sectional area and shape of said shaped plastic extrudate to reach the cross-sectional area and shape of said calibration unit within a tolerance T of the point of entry of said shaped plastic extrudate in said calibration unit, wherein T is ±0.2 cm, and g) passing the foamed shaped plastic extrudate obtained at the end of step (f) in said calibration unit,