Prefabrication experiments - 83- Reinforced concrete and the waffle slab

One of the enduring themes of modernity in architecture is the open plan. Le Corbusier’s DOM-INO system (1914) is still emblematic of this concept in architecture. The flat slab construction elucidated by DOM-INO was developed by structural engineers at the end of the 19^th century and the beginning of the 20^th century. Julius Kahn patented a reinforced concrete slab in 1903. The open plan, a result of new building techniques, was the architectural expression of horizontal liberated space. This revolution completed the progress from wall-based architecture to skeletal see-through architecture. The open post and slab also yielded countless precast systems of components geared to easily juxtaposing pre-made elements toward an infinitely variable architecture.

The steel, wood or concrete post and beam skeleton symbolized the modern open plan spatial organization, which users could adapt to their evolving needs. As many architects explored this new language of transparency, others turned to the semantic of open-ended building systems. Angelo Mangiarotti, an Italian architect was particularly proficient in developing precast component based systems. From the BRIONA construction system to his U70 system, Mangiarotti combined his talents for design with a passion for industrial production to conceive precast concrete components for panels, posts and beams. Another Italian, Pier Luigi Nervi also showcased industrial components leveraged toward open spaces. His waffle slabs for the Gatti wool factory and the Palazzo del lavorro exemplify the evolution from the simple flat slab to complex prestressed mushroom slabs and fantastically open spaces. 

While architects and engineers explored these component-based systems, many were patented and mass-produced while others remained impractical. The umbrella slab alternately referred to as the mushroom slab developed directly from the flat slab also derived a series of precast systems for building. The US patent - US 3788012 A, incorporated a square or rectangular waffle slab as a column capital supported by a central post or mast. The flat waffle floor mushrooms could be juxtaposed and assembled in orthographic directions both horizontal and vertical. The prefabricated elements could be delivered on site and quickly organize an open structural system based on the principles of the open plan: liberating space, function and envelope aesthetics.

Image from US patent - US 3788012 A