clerestory

Clerestory refers to the upper portion of a building's wall that contains a band of windows above adjacent rooflines, intended to admit daylight and, in some cases, provide ventilation. The term is thought to derive from Old French clerestorie, from Latin clarus meaning clear, reflecting its function of making the interior space clearer by daylight.

In churches and basilicas, the clerestory sits above the nave arcade and, in classical plans, above the triforium; the high windows illuminate the central space while preserving wall strength and supporting the roof. Typical layouts place the clerestory above the aisles, with the nave taller than the side aisles; the wall below the windows may be continuous or divided by columns and arches.

Historically, clerestories appeared in ancient and Byzantine architecture and were developed in Romanesque and Gothic architecture, where expansive stained-glass windows multiplied the effect of light in the nave or choir. In Gothic cathedrals, the clerestory contributes to the vertical emphasis and luminous interior characteristic of the style.

Beyond ecclesiastical use, clerestories appear in secular buildings such as libraries, museums, and offices, where high windows provide daylighting while maintaining privacy and wall strength. Modern examples include continuous strip clerestories and operable skylights, used to maximize natural light and reduce artificial lighting.

Notable examples include the clerestory windows of Chartres and Notre-Dame in the Gothic period, and certain bays of Canterbury Cathedral, illustrating how light, height, and transparency are integrated into traditional design.