Many buildings, especially in the Europe, have horizontal gaps in their walls. For example, the walls of the Royal School of Mines and the Victoria and Albert Museum in South Kensington (See attached images).
Why do these gaps exist? Are they similar to ventilation gaps or are they there for some specific structural strength reasons?
It is a decoration formed by the additional decorative elements on the main structural elements to create artistic looks.
The decorative element is usually a geometric pattern arranged in a symmetrical manner, in this case - repetitive horizontal strips floating above the main structures below to create grooves in between and create 3D effect. It is mainly for the esthetic of the building's appearance.
These are architectural features. some of them reflect the design of the stones carved and placed by artisan masons, some are pure esthetic lines and articulation.
From early Roman and Greek times the architects and masons followed certain geometry and proprtions such as golden rule of dividing rectangulars or details and design of large domes and proprtion and design of the columns.
After freedom from the confines of massive buildings working under gravity, by intruduction of steel frame, the architect have had freedom in design.
In my opinion. This looks like the breaks are at the junctions of stacked blocks. This intentional recess potentially hides any error in the vertical face alignment of the stones. Imagine, stacking stones and having the front flat faces misaligned due to manufacture.
I designed a part that was ramped, but it had a stepped parting line due to a feature on a flat face (spanning the part centerline). The Manufacturing Engineer recommended hiding the parting line by stepping the ramp the width of the flat and offset from the center of the part thereby hiding the, now flat, parting line. Less expensive mold design.
Or do you mean out of sight ? To get a large interior span with no support columns , truss celling/floors may be used. As I remember the Aon (former Amoco) building has nearly 4 foot deep trusses to give about 30+ foot spans. Some utilities are in the space. It has 83 floors and is taller( 1136') than the Hancock building (Chicago) which has 100 floors(1128') but much shorter spans.
