Typical Southern Railway vans had a vari-curve roof (inherited from the SE&CR) which had tight curves at the edges but flatter on top. The design later proved to be problematical due to 'racking' which caused the roof boards to move, resulting in leakage. The vans were the second most numerous wagon on the Southern Railway, replacing tarpaulined open wagons, and were made in several batches with variations.

One very obvious style change, dating from late 1938, was the 2+2 planking. This consisted of two narrow planks followed by two wide ones, then two narrow, and so on. Before the war, 1,800 were built with this design feature but more were built in a simplified form after hostilities. At least 67 vans went new to the War Department and more followed. Most ended up on various military railways after the war and some remained abroad. During the war over 1000 were ordered by the Railway Executive Committee for use on the LMS and GWR.