Cosmopolitan cities around the world share a striking material homogeneity. The skylines of New York, Tokyo, London, Dubai, and Hong Kong are dominated by a single material: glass. It has become practically synonymous with contemporary architecture itself. Beyond serving as a mere enclosure material, glass symbolizes the transparency and bold optimism of the 20th century.
But a different material is challenging the prevalence of the crystalline towers that have defined our cities for so long. Precast concrete is appearing on an increasing number of high-profile projects. A confluence of causes has led to this shift toward precast, from economic to political. But undergirding these reasons for this recent development is a growing sense that architects, developers, and the public are longing for more texture, variety, and depth from their buildings. Architects are beginning to seek a material palette beyond the familiar realms of glass and aluminum. This trend signals a shift in material and cultural priorities away from the stark surfaces of modernism toward a more diverse and varied architectural expression.
Prior to the advent of the glazed curtain wall at the start of the 20th century, urban building enclosures in Western cities were largely integral to their structure. Exterior walls were load bearing and crafted from heavy masonry, like stone and brick. The principal architectural issue with this construction method was that it precluded large openings, resulting in deep, dark interiors through which light struggled to penetrate—the weight of the masonry was palpable. One advantage of masonry was its expressive character, from rusticated granite podiums to richly figured limestones and colorful brick courses.
After the Industrial Revolution, façades were liberated from the task of supporting the building as cast iron and steel-reinforced concrete technologies supplanted load-bearing masonry. The lithe cast-iron columns that adorn neighborhoods like SoHo in Manhattan permitted light to penetrate deep into the floor plate. This evolved into a decoupling of the enclosure from the building structure and the advent of the glass curtain wall.
The curtain wall was revolutionary because, instead of supporting itself or the wall bearing the load of the building, it hung from slab edges. This minimized the size of the necessary structural framing while maximizing the available surface area for glass cladding. From the moment Mies van der Rohe proposed his 1921 Friedrichstrasse Skyscraper Project with its invisible façade in Berlin, glass was on its way to captivating the imagination of architects the world over. His theoretical proposition for a transparent building foreshadowed the aspirational architecture that would come to dominate the 20th century.
Precast concrete enclosures did not come into prominence until the heyday of Postmodernism in the 1970s. Precast was the simplest way to clad large areas of the façade with masonry, which was the dominant material of the historical periods that the style emulated. However, Postmodern architecture’s ironic imitation of classical architectural tropes ran only skin deep. The precast panels that hung from the building provided no structural support, just like the Modernist curtain walls the style was attempting to reject. In the years following Postmodernism, the use of precast cladding waned as a more minimal and modern aesthetic prevailed in cities again, with the rise of the Information Age.
Precast is regaining ground for several reasons, chief among them being its low cost per square foot. Cost-conscious developers are constantly seeking ways to save on construction expenditures. Value-engineering exercises have become de rigueur on large projects, and precast is an inexpensive alternative to cladding opaque zones with opacified insulated glass units or finished metal panels, which require intricate independent framing and mechanical attachments. Additionally, the fabrication of precast panels is relatively simple compared to the hundreds of pieces that constitute a curtain wall, and concrete is an inexpensive building material compared to glass or finished metal. Panel formwork can be reused many times prior to disposal, limiting waste and saving time, and the two-stage sealant used in panel joints is less intricate than the interlocks between curtain wall units.
Another reason precast is gaining ground is the evolution in energy codes. The prescriptive compliance path of some newer energy codes in the U.S. specifies a maximum window-to-wall ratio of 40%, which offers energy savings when coupled with the stringent minimum R-values at opaque zones. As a result, building elevations are featuring more opaque surface areas than the glass towers constructed over the last half-century.
However, precast systems are no thermal silver bullet. Concrete does not provide much insulation compared to advanced IGUs filled with argon gas, so precast enclosure systems typically rely on foil-faced insulation pinned to the interior surface of the panel and applied in the field. The air seal of the system is the foil-faced scrim, which is delicate and requires continuous field-applied tape at every joint. This additive insulation is also notoriously difficult to install continuously past floor slabs and in front of deep spandrel beams or wide columns. Spray foam offers an insulation alternative, but most products are flammable, do not allow for differential movement between slabs, and require controlled environmental conditions during installation. Sandwich panels, where insulation is incorporated within the precast panel itself, exist but are far from industry standard.
However, the most encouraging reason for the interest in precast is the desire by architects to innovate and explore concrete’s potential as an expressive material. Instead of following in the footsteps of the Postmodernists by facing panels with stone veneers to mimic masonry construction, contemporary architects are opting to celebrate the material itself. Brilliant examples abound in New York City alone. Disclosure: My firm, Heintges, and I have previously worked as a building envelope and curtain wall consultant for the four design firms I list below, though not on these specific projects.
One such project in downtown Manhattan is the iconoclastic 130 William, designed by Adjaye Associates with architect of record Hill West Architects. Instead of finishing the outer surface of the precast panel with stone, David Adjaye, Hon. FAIA, and his team worked with precast manufacturers to develop a foam formwork that imparts an original texture. The curved forms of the arched bays that frame the openings would have been expensive to fabricate from metal, but they formed relatively easily from plywood. A dark pigment was used to tint the concrete mix and truly distinguish the building from its glassy neighbors.
Another example is just over the bridge from 130 William: Studio Gang Architects’ 11 Hoyt in downtown Brooklyn. The project by the firm led by Jeanne Gang, FAIA, also with architect of record Hill West, consists of deep scalloped panels that repeat in an elegant diagonal pattern that appears to dance across the façade. Precast was a perfect choice for the architectural parti. The efficiency afforded by reusing formwork during fabrication is concealed by the varied panel placement on the building façade.
Situated along the southern edge of Bryant Park, Bryant is David Chipperfield Architects’ first major building in New York. Its integration of sandstone and marble chips into precast panels helps reference the historical context of the neighboring buildings. Some panel faces are polished to reveal the color of the aggregate through a specialized process that David Chipperfield, Hon. FAIA, and his team developed with the precast subcontractor.
The revival of a seemingly outmoded technology through new techniques speaks to the architect’s ability to continuously seek and find originality, while working within the dynamic context of a client’s commercial priorities and changing municipal regulations. Most poignantly, the trend responds to that tacit longing for greater variation in our urban landscape and among our most important buildings.
This article has been updated to include Hill West Architects as the architect of record for the 11 Hoyt and 130 William projects. The views and conclusions from this author are not necessarily those of ARCHITECT magazine or of The American Institute of Architects.
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