The original Barcelona Pavilion is believed to be the first time that stone was “hung” in the form of thin panels from an internal structure, with an airspace separation instead of mortar. In other words, it is the first case of a non-monolithic stone wall, as opposed to the solid, load-bearing masonry walls of time immemorial. The reason for using thin panels was probably to save money, as well as to be able to reuse the precious stone after the pavilion had served its purpose.
Yet, the pavilion walls also contains segments of traditional solid stone, namely at the ends of its characteristic “free” walls. This was presumably done to avoid having to expose an edge of a stone panel when turning a corner, which would reveal its thinness. It’s a simple detail, but it shows how important it was for this building to convey a desirable appearance over and above its constructional reality; in essence, to establish a certain decorum. It was built for an international exposition, after all, a type of event which is entirely scenographic. In fact, it’s known that the back-sides of the pavilion had stuccoed brick walls painted to look like stone.
I have visited this building on countless occasions, and never actually noticed that it contains both monolithic as well as superficial stone, and that the only way to distinguish these is by knocking on them and hearing the different sounds they make. For once, hearing is believing.
Purists take note: even the original Barcelona Pavilion was never entirely “truthful” in terms of its construction.