Cathedral of Monreale, Italy, covered with
mosaics
Ancient world Clerestories appear to originate in
Egyptian temples, such as the
Great Hypostyle Hall, where the lighting of the hall of columns was obtained over the stone roofs of the adjoining aisles, through gaps left in the vertical slabs of stone. They appeared in Egypt at least as early as the
Amarna Period.
Minoan palaces in
Crete such as
Knossos employed
lightwells in addition to clerestories. According to the
Hebrew Bible,
Solomon's Temple featured clerestory windows made possible by the use of a tall, angled roof and a central . The clerestory was used in the
Hellenistic architecture of
classical antiquity. The Romans applied clerestories to
basilicas of justice and to the basilica-like
thermae and palaces.
Early Christian and Byzantine basilicas Early Christian churches and some Byzantine churches, particularly in Italy, are based closely on the Roman basilica, and maintained the form of a central
nave flanked by lower aisles on each side. The nave and aisles are separated by columns or piers, above which rises a wall pierced by clerestory windows. ,
Wiltshire, England. The nave wall is divided into three stages: the upper stage with windows is the clerestory, beneath it is the triforium, and the lowest stage is the arcade.
Romanesque period During the
Romanesque period, many churches of the basilica form were constructed all over Europe. Many of these churches have wooden roofs with clerestories below them. Some Romanesque churches have
barrel-vaulted ceilings with no clerestory. The development of the
groin vault and
ribbed vault made possible the insertion of clerestory windows. Initially the nave of a large aisled and clerestoried church was of two levels:
arcade and clerestory. During the Romanesque period, a third level was inserted between them, a gallery called the "
triforium". The triforium generally opens into space beneath the sloping roof of the aisle. This became a standard feature of later Romanesque and Gothic large abbey and cathedral churches. Sometimes another gallery set into the wall space above the triforium and below the clerestory. This feature is found in some late Romanesque and early Gothic buildings in France. The oldest glass clerestory windows still in place are from the late eleventh century, found in
Augsburg Cathedral in
Bavaria, Germany.
Gothic period in northern France In smaller churches, clerestory windows may be
trefoils or
quatrefoils. In some Italian churches they are
ocular. In most large churches, they are an important feature, both for beauty and for utility. The
ribbed vaulting and
flying buttresses of Gothic architecture concentrated the weight and thrust of the roof, freeing wall-space for larger clerestory
fenestration. Generally, in Gothic masterpieces, the clerestory is divided into
bays by the vaulting shafts that continue the same tall columns that form the arcade separating the aisles from the nave. The tendency from the early Romanesque period to the late Gothic period was for the clerestory level to become progressively taller and the size of the windows to get proportionally larger in relation to wall surface, emerging in works such as the Gothic architecture of
Amiens Cathedral or
Westminster Abbey, where their clerestories account for nearly a third of the height of the interior. == Today ==