Abstract: Baking pit furnaces have flues cast in several inter-related parts in refractory concrete and which are assembled from the cast parts which are compacted during casting in mould means by inducing small vibrations at high frequency to the moulds in which they are cast; flues assembled from the cast parts preferably include baffles extending between side walls thereof midway of their lengths and means tying the side walls together over each length thereof defined between a control baffle and each of the two end walls of the flue. Central baffles may be rooted in the bottom walls of the flues, and all corners and free baggle edges are preferably rounded. Directional vanes are disclosed with the free baffle edges, each of said vanes being of arcuate cross-sectional shape and extending between the side walls of the flue spaced from the associated free baffle edge.