Southern Railway inherited a variety of coach stock that had been used by other railway companies pre-grouping. Furthermore, Southern Railway continued to build new coaches to the design of the three largest companies. The Maunsell carriage was intended to be the standard carriage design for use across the Southern Railway lines, incorporating the best features of each of the former companies' designs. Maunsell Coaches were constructed between 1925 and 1936 at Eastleigh, with 1200 being built.

The standard coach design was 59ft long and made from wood with steel sheeting. One feature of the coaches was the low window placement which while less of an issue when seated, meant that whilst stood up it was difficult to see outside the coach without ducking. In 1929 this feature was amended, resulting in the introduction of 'high window' coaches, although on corridor coaches the low windows remained on the compartment side of the coach. In operation, coaches were grouper together to form sets. The intention was that coaches would remain in these sets for long durations, with the set numbers appearing at the brake end of the set. 139 sets were created with loose stock being used to supplement the sets on busier trains.

In August 1925, construction began on six First Class Dining Saloons for the Western Section. The first of a batch of twenty-six such vehicles under Diagram 2651, they were intended for the London-Bournemouth, London-Portsmouth and London-Exeter services and were of the low-windowed design. Seating twenty four passengers in four seating bays at one end and the kitchen, pantry, service vestibule and side corridor at the other, a set of double loading doors opened into the vestibule, while the passengers accessed the Restaurant from the gangways at either end.

Four further low windowed Dining Saloons were completed between July and December 1929, intended for the inter-regional through sets and in May/June 1930, ten further Dining Saloons entered service, under Order 464, on West Country workings.