Post 171 –by Gautam Shah




Akhmenu festival hall, Karnak, Egypt

Clerestory is an upper level opening in a building formed either by split-level roof slabs or by a series of windows. A clerestory opening rises above adjacent roofs so provides illumination to the core section of the building. Such natural lighting system requires some form of manipulation at roof level, which however, is not possible in lower sections of multi storey buildings such as the ancient Roman apartment blocks. Clerestory openings are very important for illuminating deep interiors of vast spaces.




Historically, a clerestory denoted an upper level of a Roman basilica or of the nave of a Romanesque or Gothic church, the walls of which rise above the roof-lines of the lower aisles, and is pierced with windows.

Baths of Diocletian Paulin

Baths of Diocletian Paulin

One of the earliest clerestory openings was created for the hypo-style hall of King Seti I & Ramses II at the Temple of Amon, Karnak, Egypt. Here the central rows of columns were higher then the peripheral set of columns permitting light from the difference in elevation.


Roman, Byzantine and Early Christian buildings have clerestory windows at the base of a dome or vault. Clerestory openings were well articulated in Romanesque and Gothic periods, but interiors with large stained glass windows did not require clerestory illumination as it disturbed the picturesque effect. Side windows however, reached close to the Gothic vault. Clerestory openings made the upper section of the structure physically light weight, and visually ‘celestial’.

Clerestory windows of Amiens


During Industrial revolution period several New types of buildings were developed. These were industrial plants, ware houses, and transport terminus like bus, railway and port stations. The development also was first due to the availability of structural steel and in later periods to the cement concrete technology, both of which facilitated large span structures. The large span spaces used Skylights and North-lights for illuminating and ventilating deep spaces. Industrial plants and sports facilities use clerestory openings for shadow less and nearly consistent level of illumination in interior spaces. Clerestory openings were a necessity as roof hole like openings were technologically not feasible and materials for constructing transparent roofs or clear domes were available.

Farmers New-market store Side roof Lights

The charm of open sky top of roof level opening was replicated in vehicles like train and tram carriages and automobiles.

Tramway Roof light




An architectural opening occurs within a barrier or at the junction of two distinctive barriers. A very strong barrier provides for equally important opening. Doors, windows, gates, gateways, etc. are openings within barrier systems such as: walls, fencing, fort walls, enclosures, partitions, dividers, etc. Barriers are continuous entities, and can only be experienced through the openings. Barrier systems define a domain, so an opening becomes the representation of the domain. Opening systems can never supersede a mother barrier system. Openings are subordinated or minor systems as these must occur within a barrier system.

SCALE OF OPENINGS: An opening is a finite entity with definite size, however, the barrier system within which it manifests could be infinite in size. An opening can never be larger or equal to the barrier system within which it resides. An opening, occurring in a finite barrier system could be relatively small or large, but openings occurring in very large or infinite barriers can be judged to be large or small in terms of the user.


A small opening makes a barrier system very evident, whereas a large opening or multiple openings make barriers less effective. The exchange occurring across a small opening is very intense, compared to a large gateway. Small openings due to their smaller scale allow a controlled scale of exchange. However, a large opening often requires re-scaling through various appendages such as: segregation channels for up – down, and fast -slow traffic, compaction through funneling, filtration for selective processing acceleration and de-acceleration mechanisms.


A large window is divided into smaller units –lites, each of which can have a varied configuration. Entrance foyers of skyscrapers, lounges of Airports and Railway stations, have ganged or multiple doors to serve the demand for a wider but controlled opening. However, air hangers, garages, barns and warehouses require very wide doors to meet the functional carriage width. Very large or wide doors often have an insert small opening (‘a door within a door’) for passage. Openings are spaced out to take advantage of the location and orientation, and diffuse the exchange over a larger zone. Openings are concentrated or grouped together, to few locations to reduce the wastage of distributed operations.



Openings are scaled in terms of the image projection. A large opening means: capacity to build better, greater control over security, desire for extravagance or grandeur, need to be perceptible from distance. Smaller and fewer openings mean: conservative building technology, problems of safety and security, prudence and need to be less visible.




A Large window illuminates the interiors brightly, creating a fearless but public (non-private) space. Bright spaces are warm, a desirable quality in some climates. A Small window mean a sturdy and stable structure, an intimate (private) space, safety, security and cool interior or a ‘cold’ space. Walls, traditionally have been massive entities, so fewer openings disrupt a wall less.

LEVELS OF OPENINGS: Openings are essentially of two types: negotiable for egress or transit-able in an emergency. In both cases, the degree of conveyance may have been intentionally made difficult or easier. A French window is a door for conveyance, and a trapdoor or a hatch door is a window for all purposes. A door could occur at a negotiable level but a barn door for fodder, is placed at first floor level. A warehouse gantry girder could extend out of an upper level door like opening to lift up goods and bring it in. Windows have many grades, of ‘high to low’ sill levels, as referenced from interiors or exteriors. A high sill from interior space cuts off the view to the outside as in medieval cathedrals. A low sill or zero sill window ‘opens’ a space as in case of traditional Japanese houses. The upper floor windows of a glass curtain high rise building, clerestory windows and skylights offer a static view, lacking in dynamism.