In 1952, the double-decker design, exemplified by the '54 Ventoura Loft Liner rig seen below, made its debut. The main level bedroom area of these units had an extremely low ceiling (something like 6 feet). A 3 or 4 foot high "loft", serving as a second (bedroom) level, was accessed by a set of stairs.
Above and below we witness the Ventoura Loft Liner, one of the early "split level" trailers. The low ceilings of loft-type bedrooms made such quarters feasible only for use by children. An adult would surely have gotten claustrophobia!
We created a cut-away view of the split-level Loft Liner. Rigs such as this were made fairly obsolete by the introduction of the 12-wide, in 1960.
-Click on image for a larger view-