A turbine housing assembly for a turbocharger comprising: an inner shell comprising: an inner base portion (203, 205) defining an inlet; and a volute portion (213, 215) defining an outer contour of a volute in fluid communication with the inlet; an outer shell (206, 208) circumscribing the volute portion in a radial plane aligned with or parallel to a plane in which a turbine wheel may rotate and including an outer base portion (223, 225) circumscribing the inner base portion, wherein: the inner shell comprises a first plurality of sheet metal structures (202, 204) joined to one another in the radial plane; the outer shell comprises a second plurality of sheet metal structures (206, 208); and first portions of the second plurality of sheet metal structures surrounding the volute portion are joined to one another in an axial plane transverse to the radial plane, the axial plane being aligned with or parallel to a turbine wheel rotational axis, characterised in that a first extension (d 1) of the inner base portion perpendicular to the turbine wheel rotational axis is greater than a second extension (d 2) of the outer base portion perpendicular to the turbine wheel rotational axis; and a third extension of the outer shell along the turbine wheel rotational axis distal to the turbine wheel is greater than a fourth extension of the inner shell along the turbine wheel rotational axis distal to the turbine wheel. an inner shell comprising: an inner base portion (203, 205) defining an inlet; and a volute portion (213, 215) defining an outer contour of a volute in fluid communication with the inlet; an inner base portion (203, 205) defining an inlet; and a volute portion (213, 215) defining an outer contour of a volute in fluid communication with the inlet; an outer shell (206, 208) circumscribing the volute portion in a radial plane aligned with or parallel to a plane in which a turbine wheel may rotate and including an outer base portion (223, 225) circumscribing the inner base portion, wherein: the inner shell comprises a first plurality of sheet metal structures (202, 204) joined to one another in the radial plane; the outer shell comprises a second plurality of sheet metal structures (206, 208); and first portions of the second plurality of sheet metal structures surrounding the volute portion are joined to one another in an axial plane transverse to the radial plane, the axial plane being aligned with or parallel to a turbine wheel rotational axis, characterised in that the inner shell comprises a first plurality of sheet metal structures (202, 204) joined to one another in the radial plane; the outer shell comprises a second plurality of sheet metal structures (206, 208); and first portions of the second plurality of sheet metal structures surrounding the volute portion are joined to one another in an axial plane transverse to the radial plane, the axial plane being aligned with or parallel to a turbine wheel rotational axis, characterised in that a first extension (d 1) of the inner base portion perpendicular to the turbine wheel rotational axis is greater than a second extension (d 2) of the outer base portion perpendicular to the turbine wheel rotational axis; and a third extension of the outer shell along the turbine wheel rotational axis distal to the turbine wheel is greater than a fourth extension of the inner shell along the turbine wheel rotational axis distal to the turbine wheel.