Abstract: A ceiling of a cavity is provided with contiguous portions, including a central portion defined entirely by edges, and peripheral portions defined by edges and by a portion of a frontier of the ceiling. For the central portion, a capital is defined by facets that bear against the central portion edges and converge towards an apex, and a slender support column is centered on the apex and extends from the capital to a floor of the cavity. For each peripheral portion, a capital is defined by facets that bear against the peripheral portion edges and converge towards a terminal edge extending in a plane normal to a wall of the cavity, and a support rib extends in the normal plane between the terminal edge of the capital and a wall of the cavity. The method includes manufactured the part while making the above-defined supports and capitals by additive manufacturing.