Abstract: There is disclosed a method of manufacturing a semi-annular component 60 for a casing arrangement of a gas turbine by additive manufacture, the component having a lattice structure 84 and extending circumferentially about a central axis 11 so that a radial direction extends towards the central axis 11. The method comprises: fusing material at successive build locations along a build direction 98 to progressively form the component 60 so that members 86 of the lattice structure 84 have an elongate direction having a circumferential component; wherein the build direction 98 lies in a plane substantially normal to the central axis; and wherein the build direction 98 is inclined with respect to the radial direction at each build location so that members 86 of the lattice structure 84 are progressively formed along their elongate direction. A semi-annular component including a seal carrier is also disclosed.