In his lectures at the University of Pennsylvania, Louis Kahn loved to recount an imaginary dialogue with the material he was about to use: "Ask the brick what it wants to be. The brick says: I like an arch. And if you say to it, arches are expensive, I can put a concrete lintel over you instead — what do you think, brick? The brick says again: I like an arch." The anecdote, often quoted out of context as a rhetorical flourish, actually expresses a precise design principle: every material has a structural and formal logic that's its own, and the designer's task isn't to impose an alien form on it but to listen to what that material, given how it's made, does best.
Reading a brick wall
Before looking at how three different architects have interpreted brick, it is worth learning to read a wall. Brick is clay that has been shaped, dried and fired in a kiln at temperatures of around 900–1100 °C, depending on the mix and the colour desired. The traditional Italian format, the solid brick, measures about 25 × 12 × 5.5 centimetres: a proportion designed so that the length equals two widths plus a joint, allowing bricks to be interlocked through the thickness of the wall. It is this interlocking, called the bond, that tells the truth about a wall's function.
In a massive load-bearing wall the bricks are laid partly lengthwise (as stretchers) and partly end-on (as headers), so as to tie the inner and outer layers together: the headers, the short faces of the bricks visible on the façade, are the sign of this tie. Historic bonds, such as English bond, with alternating courses of stretchers and headers, or Flemish bond, with stretchers and headers alternating in the same course, arise from this structural need. A face in which only stretchers are visible, all offset by half a brick, is instead almost always a cladding one brick thick, hung from a structure of reinforced concrete or steel behind it. Neither solution is right or wrong in absolute terms; but an honest façade shows which of the two it is using, and the architects in this article, each in their own way, chose to do so.
Louis Kahn: the brick that carries itself
Kahn applies this principle most consistently at the Indian Institute of Management in Ahmedabad (1962–1974), where brick isn't a cladding but the actual load-bearing structure: huge arches and circular openings in brick masonry, substantial wall thicknesses, surfaces left raw and unplastered. The complex, built with local labour and materials in a climate that makes brick (fired with traditional Indian techniques, often in pit kilns) an economically and climatically logical choice, becomes a manifesto for the coherence between available material and architectural form. At the Phillips Exeter Academy Library (1965–1972), Kahn uses brick for the load-bearing outer envelope — piers and arches in solid brick — while reserving concrete for the double-ring inner structure that organizes the reading spaces: a hierarchy of materials that mirrors a hierarchy of uses, from protection from the outside to spatial freedom on the inside.
Looking closely at the two buildings shows how seriously Kahn took his remark about the arch. A brick arch pushes outwards, and in a thin wall that thrust would have to be resisted by massive buttresses. At Ahmedabad Kahn solves the problem explicitly: beneath many arches runs a concrete beam that acts as a tie and absorbs the thrust. Brick works in compression, concrete in tension, and both materials remain visible, each in its proper role. At Exeter the brick piers of the façade grow thinner as they rise, because the upper floors carry less weight, while the windows widen accordingly: the load can be read directly on the façade, floor by floor. The Indian project was also followed by the architect Balkrishna Doshi, who had helped bring about the commission, and after Kahn's death in 1974 it was completed by his collaborator Anant Raje.
Herzog & de Meuron: brick as texture, not as mass
Herzog & de Meuron tackle the problem from almost the opposite direction in the Tate Modern extension in London, the Blavatnik Building (2016): a 65-metre tower whose outer envelope is a lattice of bricks laid with regular gaps between them: by day it filters light into the building, by night it lets the light of the galleries show through. It is not solid load-bearing masonry as in Kahn. Brick here isn't the structure — the tower has a reinforced-concrete frame — but a visual and climatic filter, a "skin" that talks, in scale and colour, to the brick of the neighbouring Bankside Power Station, the decommissioned power station that forms the museum's main body. It's the same "phenomenological" approach that characterizes the whole studio's material research: not asking what a material looks like in the abstract, but what that specific surface does — in this case, how it filters light and how it converses with the site's industrial memory.
The idea of brick as a light filter has an important precedent a few years earlier, in Peter Zumthor's Kolumba museum in Cologne (2007). There the new building rises above the ruins of a Gothic church destroyed in the Second World War, and the walls wrapping the archaeological excavation are made of long, thin grey bricks, handmade by a Danish brickworks, laid with small openings between one unit and the next. Light enters in fragments, as through a veil, and air circulates freely. In both cases brick loses its load-bearing role but not its nature: it remains a small element that can be held in one hand, laid one at a time, and it is precisely the visibility of this human scale that distinguishes these façades from a prefabricated panel imitating brick.
Aldo Rossi and the brick of the city
Aldo Rossi takes brick in yet a third direction: that of collective urban memory. At the San Cataldo Cemetery in Modena (designed in 1971 with Gianni Braghieri, inaugurated in 1987 and never fully completed), the volumes are elementary and repeated: the large cube of the shrine, the long two-storey porticoes, the cone of the common grave that remained on paper. They are not in face brick: the cube is in red-coloured concrete, the porticoes are rendered. But the colour deliberately recalls the brickwork of Cesare Costa's 19th-century cemetery, next to which the new complex stands, and the composition evokes the typology of the traditional Italian house and city built in brick, emptied of any residential function: it is "the city of the dead" imitating the city of the living. In Rossi's theory, set out in "The Architecture of the City" (1966), brick is never a neutral material: it carries with it the typological memory of centuries of urban building in Lombardy and Emilia, and it's precisely this memory — not technical performance — that makes it the appropriate choice for an architecture that wants to be recognizable as part of the historic city, even when the function is radically new.
The thread linking these three approaches, apparently very far apart from one another, is that none of the three treats brick as a cladding interchangeable with any other material by purely aesthetic choice. Kahn listens to it as structural logic, Herzog & de Meuron use it as a perceptual filter, Rossi uses it as typological memory — but in all three cases brick carries a meaning that no other material could carry in the same way.
When Rossi does use face brick, he does so with the same intention. At the Bonnefanten Museum in Maastricht (1990–1995), built along the Meuse on a former industrial site, the museum's wings are in brick and stone, like the city's warehouses and factories, while at the centre rises a tower topped by a zinc-clad dome. Brick here does not stand for an abstract idea of tradition: it is the material of the particular city in which the building stands. That is the difference between the typological memory Rossi speaks of and a simple taste for old materials.
Italian brick after Rossi
In Italy reflection on face brick runs through the whole second half of the 20th century. Giancarlo De Carlo, in the university colleges of Urbino (the first completed in 1966, the others in the following years), used brick and concrete to build a complex that settles into the hill opposite the historic town, with terraces and paths recalling Urbino's lanes: brick is the material link with the brick city of the Ducal Palace. Mario Botta, from Ticino but trained in Venice, made brick and stone in alternating courses his signature, from Évry Cathedral in France (1995) to the San Francisco Museum of Modern Art (1995), where brick clads a large stepped volume cut through by an oblique cylinder. In these cases brick is a cladding over a concrete structure, but it is used in large continuous surfaces, with decorative bonds that openly declare its role as a skin.
What to check when specifying face brick
Face brick is often chosen by looking at a sample and a colour catalogue, but the life of a façade depends on properties that cannot be seen. The first parameter is frost resistance: the European standard for clay masonry units (EN 771-1) classifies bricks according to the exposure they can withstand, and a brick suitable for an interior or a sheltered wall may spall within a few winters if used on a façade exposed to driving rain and freeze-thaw cycles. The second is water absorption and soluble salt content, which determine the appearance of efflorescence, the white stains that bloom on new walls. The third is the mortar: it must be weaker and more deformable than the brick, so that when movements or thermal cycles occur it is the joints that crack, not the bricks. A hydraulic lime mortar, besides being more compatible, will one day allow the wall to be dismantled and the bricks recovered whole; a rigid cement mortar, by contrast, makes them almost impossible to separate without breaking them.
Finally, movement joints. A brick façade tens of metres long expands and contracts with temperature and moisture, and without vertical joints at regular intervals it cracks at random, often at the openings. Kahn, Rossi and Herzog & de Meuron solved this problem in different ways, but none of them ignored it: even the most expressive façade has to respect the physical behaviour of the material it is made of. It is perhaps the most concrete version of Kahn's question: asking brick what it wants also means asking how much it moves, how much water it absorbs and how many winters it can withstand.