A transom-mullion structure, particularly for facades or roof windows, in whose frame area glass panes (100) can be inserted, comprises several mullions (1) between which transoms (2) are fixed. Channels (3, 4) are provided on the outer surface of the mullions (1), specifically on the edges thereof, and serve to accommodate a seal (5, 6), whereby a drainage channel (7, 8) for diverting liquid is arranged adjacent to the channel (3, 4). In addition, channels (10, 11) are provided on the side of the transom (2), specifically on the edges thereof, that faces the outer surface of the mullion (1), and serve to accommodate a seal (12) and a retaining strip (13) located between the channels (10, 11). According to the invention, a connecting part (40) is attached to the transom (2) at the face thereof and serves to lengthen the channels (10, 11) and the retaining strip (13) of the transom (2) while at least partially overlapping the channel (3) located on the edge of the mullion. This configuration enables the transom to be easily attached to the mullion, whereby, for providing an overlapping design of the transom, a connecting part is easily mounted without requiring a complex notching of the transom (2).