EXHIBITION HALL, TURIN

Designed by Pier Luigi Nervi; completed 1950
The Exhibition Hall of Turin (1949–50) represents a significant achievement in the
building arts of the 20th century. Built in the city of Turin among the vestiges of war-torn
Italy, it was designed, engineered, and built by Italian engineer Pier Luigi Nervi. Widely
known for its innovative adoption of new building materials and construction techniques,
the Exhibition Hall is an eloquent example of the use of reinforced concrete and ferrocement.
The large, unobstructed spans of the main hall and the exuberant elegance of its
articulated roof structure were made possible by the pioneering efforts and structural
ingenuity of its builder. A building commissioned to showcase the promise of Italy’s
postwar industrial production called for display areas of vast dimensions, and the
undulating concrete canopy of the Turin Exhibition Hall achieved just this.
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Its construction epitomized modern architecture’s postwar fascination with structural
engineering. The building’s appearance was derived from its structural logic and process
of assembly. The elasticity and plasticity of poured-in-place concrete, the flexibility of
prefabricated ferro-cement shells, and the ability to calculate and thus control the
building’s static forces were significant factors in determining its final shape. In building
the Exhibition Hall, no boundary separated the architectural search for form from the
engineering imperative to quantify structure.
Programmatically, the Exhibition Hall was a quintessentially modern building. Along
with factories, warehouses, bridges, and power plants, exhibition halls were utilitarian
structures born of the industrial revolution. From turbine engines to plumbing fixtures,
exhibition halls collected and displayed the products of mechanization. A progenitor of
the Turin Hall was the Crystal Palace, designed by Sir Joseph Paxton for London’s Great
Exhibition of 1851; like the later Exhibition Hall, it too was built of prefabricated
components. However, unlike the Turin Hall, the Crystal Palace was built of iron and
glass and achieved interior spans of only 100 feet. Only 100 years later, the use of
reinforced concrete and ferro-cement would result in clear spans of nearly 300 feet.
An invited competition was launched for the construction of a new Exhibition Hall to be
located on the site of the former Palace of Fashion. A general urgency to rebuild existed
throughout Europe, and as the Exhibition Hall was essential in helping to generate future
economic growth for Italy, its building schedule was but a mere eight months. The lack
of building materials, particularly wood for the erection of formwork, further exacerbated
the difficult conditions under which the participants were asked to devise an architectural
solution. The existing palace, destroyed during World War II, was rebuilt by engineer
Biscaretti di Ruffia. The design commission and building tender for the new Exhibition
Hall, however, was entrusted to the engineer ing team of Nervi and Bartoli. The
economical nature of their proposal, with its inexpensive use of materials, managed use
of labor, speed of erection, and avoidance of wooden formwork, made it the favored
solution. The mastery that Nervi and Bartoli had previously achieved in the construction
of large-span structures, such as the Florence Stadium (1929–32) and the airplane
hangers of Orvieto and Orbetello (1937–43), bore confidently on the future success of
their daring proposal.
The complex was built in two stages, the first structure being completed in 1949 and
the second a year later. The initial building, Salone B (Agnelli), was spatially, materially,
and structurally the more extravagant of the two. It comprised two interconnected spaces,
the main hall a rectangular barrel-vaulted enclosure measuring 328 by 262 feet and the
smaller hall an apsidal room, with a half-dome 130 feet in diameter attached to one end
of the main hall. With respect to the cross section, the height at the center of the main hall
rose to over 60 feet, and 25-foot-wide mezzanines were built at the base of the two rows
of supporting piers. The second building, Salon C, measured 213 by 230 feet and was
also roofed with a concrete vault of both precast and poured-in-place elements.
The project’s success can be attributed to its inventive construction process. To build
during the harsh winter months and reduce the total time required for construction, Nervi
devised a three-part process wherein the first two parts proceeded simultaneously. On
site, the main structural supports of Salone B were built using poured-in-place reinforced
concrete, whereas off-site, the prefabricated sections of the vaulted roof were cast
independently using ferro-cement. Once the main structural piers and floors were in
place, the installation of the roofing members proceeded without the need for additional
formwork. The individual roof sections, measuring 8 by 13 feet and folded in the profile
of a sinusoidal wave, were aligned and arched into the desired profile of the vault and
bound to each other using poured-in-place concrete, the whole made possible by the use
of movable metal scaffolding. The final phase of construction required bonding the roof
shells to the poured-in-place piers. This was achieved via the on-site pouring of
reinforeed-concrete rib beams. They spanned from pier to pier and were poured within
the upper and lower extremities of the roof section. It was this system of in situ concrete
beams that ensured that the prefabricated roof shells and the structural piers worked
together monolithically.
Still, the most significant characteristic of the Exhibition Hall was its extensive use of
precast ferro-cement. This new material was used here for the first time in the
construction of a large-span building, and the best person disposed to do so was its
inventor, Nervi. In 1943, Nervi registered two patents for ferro-cement and built four
boats using the material. Its ability to be light in weight, thin in section, and difficult to
pierce, yet structurally sound, made it a viable alternative to wood for the construction of
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navigational vessels. Ferro-cement represented an entirely new way of conceiving roof
structures and exterior building skins. It inverted the traditional manner in which concrete
and steel were combined. Whereas reinforced concrete involved the insertion of steel
rods within the body of concrete, ferro-cement involved a concrete coating over a body of
steel. Layers of small-diameter steel mesh were intertwined and coated with a mixture of
cement mortar (cement and sand) and folded into a range of contours intrinsic to its
process of construction. The ability to bend the mesh into various shapes rendered
possible the construction of very thin yet structurally sound slabs. The roof section of the
Exhibition Hall was of an undulating corrugated profile whose strength was contained in
only an inch and a half of ferro-cement.
The Exhibition Hall is an architectural and structural marvel of the postwar era. Its
means of construction bear witness to the power of invention in the act of building and to
the hidden potential in uniting the search for form with the measure of materials.