A new conical roof building method provides flat plates having straight abutting edges and curved outer edges. The plates are placed horizontally edge to edge except for a sectoral opening. The plates are welded together to form a flat disc-shaped blank, leaving an open sector of the blank. Radial supports are welded to a top of the disc-shaped blank. A center of the disc-shaped blank is lifted, forming a conical-shaped structure, closing and abutting edges of the open sector and touching edges of the formerly open sector are welded together, completing the forming of the conical roof.