Abstract: A flat self-supporting vault for tunnel-type furnaces, particularly for baking bricks and tiles is made of mutually interconnected beams bearing at both ends on the side walls of the furnace disposed transversely to the tunnel length. Each beam is made of a number of longitudinally aligned refractory segments, also interconnected, preferably by expansion joints. Each segment is formed by casting around an inner longitudinal metal core at least long as a single beam. Each metal core, such as an I-beam of two C-beams, has an external sheath of thermo-insulating material and defines with this sheath a continuous linear passage for a cooling fluid flowing in a cooling system connected to both ends of each metal core.