Rules · Roofs · Pediments · Theory
Put a pediment only where the roof actually ends in a gable, on the short sides of a building, never along its length or stacked one above another, because the pediment represents the gable of the roof.
In the primitive hut that Laugier made the origin of all architecture, four tree-trunks carry beams, and inclined poles laid on the beams form a roof with a triangular gable at each end. Every true member of architecture (column, entablature, pediment) must therefore correspond to a part of that structure; a pediment where no roof ends is a lie. The rule condemned the broken and superimposed pediments of the Baroque and helped shape the severe Neoclassicism of the later eighteenth century. The slope of the classical pediment itself follows the low pitch of a Mediterranean tiled roof (The height of the pediment).
Weight for weight, timber is many times stronger in bending than stone; long spans in trabeated buildings are therefore roofed with timber beams resting on stone walls and columns.
bending strength ÷ density: oak ≈ 70 · limestone ≈ 3 (kPa per kg ⁄ m³)
Hold that the beauty of the orders comes from fixed proportions that please by nature, as consonances do in music; where the ancients differ, the differences answer to circumstances such as distance and height.
Give the flight of steps before a temple an odd number, so that one who starts with the right foot will also set the right foot first on the top.
Judge every building against the first shelter: four trees for columns, branches laid across them for the entablature, and a pitched roof whose end makes the pediment. These three are the essential parts; all else is added.
Let columns stand free, round and upright, carrying a straight entablature directly; do not engage them in walls, replace them with pilasters, or set them on pedestals.
Avoid the ornaments that have no model in the hut: broken or curved pediments, pediments on the long side of a roof, orders piled storey upon storey on a church front, arches carried on columns, and twisted or cabled shafts.
Cite this page Chris Paton, “A pediment is the end of a roof”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/laugier-gable-pediment. Text, drawings and models licensed under CC BY-NC 4.0.