How Upside-Down Models Revolutionized Architecture, Making Possible St. Paul’s Cathedral, Sagrada Família & More

For 142 years now, Sagra­da Família has been grow­ing toward the sky. Or at least that’s what it seems to be doing, as its ongo­ing con­struc­tion real­izes ever more ful­ly a host of forms that look and feel not quite of this earth. It makes a kind of sense to learn that, in design­ing the cathe­dral that would remain a work in progress near­ly a cen­tu­ry after his death, Antoni Gaudí built a mod­el upside-down, mak­ing use of grav­i­ty in the oppo­site way to which we nor­mal­ly think of it as act­ing on a build­ing. But as archi­tec­ture YouTu­ber Stew­art Hicks explains in the video above, Gaudí was hard­ly the first to use that tech­nique.

Take St. Paul’s Cathe­dral, which Christo­pher Wren decid­ed to make the tallest build­ing in Lon­don in 1685. It includ­ed what would be the high­est dome ever built, at 365 feet off the ground. “For a tra­di­tion­al dome design to reach this height, it would have to span an open­ing that’s 160 feet or 49 meters wide, but this made it much too heavy for the walls below,” says Hicks. “Exist­ing tech­niques for build­ing this just could­n’t work.” Enter sci­en­tist-engi­neer Robert Hooke, who’d already been fig­ur­ing out ways to mod­el forces like this by hang­ing chains from the ceil­ing.

“Hooke’s genius was that he real­ized that the chain in his exper­i­ments was cal­cu­lat­ing the per­fect shape for it to remain in ten­sion, since that’s all it can do.” He explained domes as, phys­i­cal­ly, “the exact oppo­site of the chains. His famous line was, ‘As hangs the flex­ile line, so but invert­ed will stand the rigid arch.’ ” In oth­er words, “if you flip the shape of Hooke’s chain exper­i­ments upside down, the forces flip, and this shape is the per­fect com­pres­sion sys­tem.” Hence the dis­tinc­tive­ly elon­gat­ed-look­ing shape of the dome on the com­plet­ed St. Paul’s Cathe­dral, a depar­ture from all archi­tec­tur­al prece­dent.

The shape upon which Wren and Hooke set­tled turned out to be very sim­i­lar to what archi­tec­ture now knows as a cate­nary curve, a con­cept impor­tant indeed to Gaudí, who was “famous­ly enam­ored with what some call organ­ic forms.” He made detailed mod­els to guide the con­struc­tion of his projects, but after those he’d left behind for Sagra­da Família were destroyed by anar­chists in 1936, the builders had noth­ing to go on. Only in 1979 did the young archi­tect Mark Bur­ry “imag­ine the mod­els upside-down,” which brought about a new under­stand­ing of the build­ing’s com­plex, land­scape-like forms. It was a sim­i­lar phys­i­cal insight that made pos­si­ble such dra­mat­ic mid-cen­tu­ry build­ings as Anni­bale Vitel­lozzi and Pier Nervi’s Palazzet­to del­lo Sport and Eero Saari­nen’s TWA Flight Cen­ter: pure Space Age, but root­ed in the Enlight­en­ment.

Relat­ed con­tent:

How the World’s Biggest Dome Was Built: The Sto­ry of Fil­ip­po Brunelleschi and the Duo­mo in Flo­rence

How This Chica­go Sky­scraper Bare­ly Touch­es the Ground

Why Hasn’t the Pantheon’s Dome Col­lapsed?: How the Romans Engi­neered the Dome to Last 19 Cen­turies and Count­ing

An Archi­tec­tur­al Tour of Sagra­da Família, Antoni Gaudí’s Auda­cious Church That’s Been Under Con­struc­tion for 142 Years

A Guid­ed Tour of the Largest Hand­made Mod­el of Impe­r­i­al Rome: Dis­cov­er the 20x20 Meter Mod­el Cre­at­ed Dur­ing the 1930s

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. His projects include the Sub­stack newslet­ter Books on Cities and the book The State­less City: a Walk through 21st-Cen­tu­ry Los Ange­les. Fol­low him on Twit­ter at @colinmarshall or on Face­book.