Rules · Structure · Walls · Materials
In a framed building the columns and beams carry every load; the outer wall can be reduced to a light cladding hung on the frame, floor by floor, and need grow no thicker as the building rises.
load-bearing wall: thickness grows with height · frame: cladding thickness constant
A masonry wall must carry the weight of everything above it, so it thickens toward the bottom: the Monadnock Building in Chicago (1889–91), sixteen storeys of load-bearing brick, has walls about 1.8 m thick at the base. In William Le Baron Jenney’s Home Insurance Building (1884–85) and the Chicago buildings that followed, an iron and then steel frame took over the load, and the walls became panels carried storey by storey on the frame.
Sullivan takes the frame for granted: his essay begins from the fact that steel, the elevator and fireproofing had made height a matter of economics rather than of structure. What remained for the architect was to give the frame an honest and expressive skin.
A saddle surface in which two opposite corners are raised and two lowered is a hyperbolic paraboloid; it contains two families of straight lines, so it can be formed with straight boards and yet has double curvature.
y = k·x·z (or any bilinear patch through four points not in one plane)
A thin curved shell carries load by the membrane forces in its surface, not by bending; so shape it to its loads and supports, and it can span great distances with a thickness of a few centimetres.
span ÷ thickness of a good shell ≈ 400–1000 (an egg: ≈ 100)
Span the whole depth of the building with the structure so that each floor is a single open plate, adaptable to uses that cannot be foreseen.
Pompidou: 48 m clear span between column lines, 13 bays of 12.8 m
A new material calls for new forms: iron should be used in slender members that show its strength in tension and bending, not cast in imitation of stone columns and vaults.
Omit applied ornament from buildings and everyday objects: it wastes work, money and material, dates quickly, and adds nothing that fine material and exact workmanship cannot give.
Build the house as a standard skeleton of flat concrete slabs, a few columns set back from the slab edges, and a stair; everything else (walls, windows, partitions) is infill that can be placed freely.
3 slabs + 6 columns + 1 stair
Cite this page Chris Paton, “The skeleton carries; the wall only encloses”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/skeleton-frame. Text, drawings and models licensed under CC BY-NC 4.0.