Abstract: The ceramic shell of a stove encloses a firing chamber and a helical flue gas passage and is composed of superimposed blocks, each of which has the same cross-sectional shape as the corresponding height portion of the shell. The bottom block consists of a bottom tub. The uppermost block consists of a cover provided with a smoke outlet for connection to a smoke pipe. The intermediate blocks comprise at least one set of blocks which are substantially identical in shape. In order to facilitate the building of the stove and to ensure an improved utilization of the heat of the flue gases, each of the blocks has in each end face confronting an adjacent block an annular groove, which is covered by the adjacent block and contains a refractory sealing cord, which seals the joint between said adjacent blocks. The firing chamber is surrounded by a refractory insert structure, which is disposed within the blocks that surround the firing chamber.