Kahn Building

The Kimbell Art Museum’s original building, designed by Louis Kahn and opened to the public for the first time in 1972, has become a mecca of modern architecture. 

The Board of Directors of the Kimbell Art Foundation commissioned Louis Kahn as the Museum’s architect in 1966. Working closely with the Kimbell's first director, Richard F. (Ric) Brown, who enthusiastically supported his appointment, Kahn designed a building in which “light is the theme.” Natural light enters through narrow plexiglass skylights along the top of cycloid barrel vaults and is diffused by wing-shaped pierced-aluminum reflectors that hang below, giving a silvery gleam to the smooth concrete of the vault surfaces and providing a perfect, subtly fluctuating illumination for the works of art.

The main (west) facade of the building consists of three 100-foot bays, each fronted by an open, barrel-vaulted portico, with the central, entrance bay recessed and glazed. The porticos express on the exterior the light-filled vaulted spaces that are the defining feature of the interior, which are five deep behind each of the side porticos and three deep behind the central one. Additionally, three courtyards punctuate the interior space. Though thoroughly modern in its lack of ornament or revivalist detail, the building suggests the grand arches and vaults of Roman architecture, a source of inspiration that Kahn himself acknowledged. The principal materials are concrete, travertine, and white oak.

STRUCTURE

“The room is the beginning of architecture.”—   Louis I. Kahn

           One of the architect’s fundamental tasks is formulating the structure, or arrangement of forms, that the building will assume. Each architect has an individual approach to developing that initial concept. Kahn is often quoted as first asking, “What does this building want to be?” He believed that the essence of the structure started with the room, and thinking about how that space would be used and how it should feel. From that point, the building evolved as a “family of rooms” with a simple plan based on classical proportion, repetition, and variation.
            In the case of the Kimbell, director Richard Brown provided an initial list of important considerations for generating ideas for the structure. In that “Pre-Architectural Program,” Brown specifically stated that “natural light should play a vital part in illumination.” This stipulation, along with Kahn’s own strong interest in the use of natural light, resulted in Kahn’s early concept of a room with a vaulted ceiling that would allow natural light to enter the space from above. The vault also appealed to Kahn’s admiration for ancient structures—from Roman arches and storage warehouses to Egyptian granaries.
            Kahn determined the exact shape of the vault through his collaboration with a structural engineer, Dr. August E. Komendant. As opposed to semicircular vaults, the cycloid vault has gently rising sides that give the impression of monumentality without overpowering the visitor. By mathematical definition, the cycloid is the curve traced by a point on the circumference of a circle that rolls on a straight line without slipping. This geometric form is capable of supporting its own weight and has been likened to an eggshell for its ability to withstand heavy pressure. At the Kimbell, the weight for each vault is directed through four corner columns measuring two square feet. Unlike classical precedents, Kahn’s vaults are interrupted at the top by skylights and require concrete struts that connect the shells at ten-foot intervals. Additionally, Kahn and his engineers placed long steel cables inside along the length of each vault. After the concrete had hardened for a week, hydraulic jacks were used tighten the cables to create a system of post-tensioning that distributes and supports the weight of the roof—similar to a suspension bridge.
            Like classical buildings (such as the Parthenon), the Kimbell’s structure is based on a consistent mathematical model. The basic plan is composed of sixteen cycloid vaults (100 x 20 feet) that are arranged in three parallel units of six, four, and six in the Kimbell. Other elements are based on a ratio of 20 to 10. For example, on the floor, wood sections measure 20 feet and travertine sections are 10 feet. The building is based on these “rules” of logic, enabling the visitor to easily follow and “read” the structure.
           Although the structure is based on a simple plan of unadorned, repeated forms, Kahn also introduced variations on those basic forms and “themes.” The porticos at the Kimbell’s entrance on the west side of the building first introduce the vault to the approaching visitor and demonstrate the form’s versatility. Within the Museum, visitors see that vaults cover the galleries, an auditorium, and the Buffet Restaurant. Kahn also varied the size of the courtyards. The North courtyard is 40 square feet, while the South courtyard is 20 square feet.
            The “rooms” were designed to relate to the visitor on an intimate level to enhance their experience of the artworks on view. The space, in fact, was designed to be as flexible as possible within the confines of the vaulted spaces. Moveable walls can be attached to the soffits (the underside joint between arches) in various configurations to best suit the Museum’s display needs.

MATERIALS

“Natural materials have a way of blending together.”—Louis I. Kahn

           To make a structure that will stand the test of time, architects choose materials that are strong and durable, as well as pleasing to the eye. Kahn preferred simple forms and natural materials. To achieve a sense of serenity and elegance in the Kimbell, Kahn selected materials that complemented each other in tone and surface: travertine, concrete, white oak, metal, and glass. Simple and unadorned, each of these materials shows its innate character by its variation of texture.
            Concrete, according to Kahn, was “a noble material if used nobly.” Revolutionizing the modern use of materials, Kahn viewed concrete as both an aesthetic and structural choice. In the Kimbell’s galleries, concrete vaults shimmer with light to create a subtle luminosity that Kahn compared to a “silvery powdered moth’s wing.” Reinforced concrete also supports the weight of the structure in the form of vaults, walls, and piers. Creating the right look to the concrete was a matter of serious importance to Kahn, who went to great lengths to select the proper color (soft gray with lavender tones) determined by the mixture of sand and cement. Numerous wall tests were poured and allowed to cure in the Texas sun until they found the right surface qualities and perfect match for the soft tones of the travertine. Kahn believed that buildings should tell the story of how they were made and that incidents of the construction process should be left as a visual record. Accordingly, when they occurred, marks from plywood mold forms, bits of rubber, and air pockets remain for all to see (although the workmen practiced to attain perfection).
            Travertine, on the other hand, acts only as “in-fill” material. Kahn even called it wall paper. (Glass and wood are also non-weight-bearing materials in the Museum.) The travertine (a type of colored limestone) used for the Kimbell was imported from Tivoli, near Rome, Italy. This material is riddled with irregularly shaped holes left by gases and pieces of vegetation trapped in hardened layers of calcium carbonate. Despite its “Swiss-cheese” texture, travertine is a durable material and has been used since antiquity for countless buildings. Kahn was deeply influenced by monuments and ancient ruins that he studied as a student and sketched on his travels through Italy, Greece, and Egypt. In his own buildings, Kahn used such materials as travertine to emulate the timeless and monolithic qualities he so admired in those ancient structures. Over one million pounds of travertine sheath much of the Kimbell’s interior and exterior walls, gallery floors, porches, and stairs. These thin, rough-hewn pre-cut slabs (5/8 inches thick) were shipped from Italy in 17 boatloads over nine months. Fissures and openings were not filled. Every attempt was made to retain the material’s natural appearance.
            Lead was selected for the roof cover for its color, dull sheen, and discreet, natural appearance. Because this soft metal ages quickly, Kahn believed that it would look consistent with the travertine and concrete. In keeping with his palette of warm and cool tonal harmonies, Kahn also selected white oak for the gallery floors, doors, and cabinetry; anodized aluminum (a light-weight metal noted for its high reflectivity that has been covered with a protective oxide coating) for the soffits and reflectors; and mill-finished steel for windows and door frames, elevators, and handrails, as well as in the kitchen, conservation studio, and darkroom. The Kimbell’s uniquely shaped handrails are made of folded metal, because Kahn preferred emphasizing the sheet quality of the material instead of pretending that it was worked like a solid material, such as wood. 

LIGHT

“No space, architecturally, is a space unless it has natural light.”— Louis I. Kahn

           A person’s experience of an architectural space is shaped by many factors, including its scale, proportions, plan, and use of materials. In many buildings, and especially at the Kimbell Art Museum, light performs a crucial role—illuminating the space and creating a mood. In his teachings and designs, Louis Kahn constantly stressed the importance of light in relation to structure. Natural light, “dynamic, ever-changing,” he preferred above all other sources of illumination.
           Many museum designs primarily rely on artificial lighting to prevent direct sunlight from damaging priceless and delicate works of art. Kimbell director Richard Brown, however, felt that natural light should be used to illuminate museum spaces so that visitors may be able to relate to nature and the effects of changing weather while inside the Kimbell. This type of lighting also enables the visitor to see the work of art more similarly to the way it would have been viewed by its creator, under conditions of natural light. Kahn and Brown met well on this topic, which became the inspiration for Kahn’s concept of the cycloid vault with “narrow slits to the sky” that allowed natural light to enter and transform the space. However, the works of art are not illuminated entirely by natural light—lamps bolster the daylight to give a mixture of natural and artificial light that is ideal for viewing works of art.
           In order to allow light to enter the space without endangering precious artworks, Kahn envisioned a metal “reflector” or “shield” that would be placed directly beneath the skylights to reflect sunlight onto the smooth, gray, curved surface of the vault. As if by magic, the light would transform the surface, creating a silvery luminosity that filtered down and filled the space below without harming the Museum’s collection. Lighting consultants worked with Kahn to devise gull-wing shaped reflectors that are now installed in the Kimbell. These “natural light fixtures,” made from pierced aluminum, were curved to simultaneously reflect and filter the Texas sun. For works of art that require very low levels of light (drawings or Asian scroll paintings, for example), black felt can be used to cover the skylights to further reduce the amount of light reflected into the gallery.
           Kahn incorporated slender lunettes at either end of each vault for more light. The lunette also acts as an important element that separates distinct parts of the structure and is, in turn, shaped by those parts. Its underside echoes the cycloid, while the topside is shaped by the concrete shell that thickens at its apex. Therefore, the topside of each lunette expands at the bottom and becomes thinner at the top. Light slots run along the entire bottom length of the vault to allow indirect sunlight to enter Museum spaces. Kahn also designed three courtyards, named after the kind of light that he anticipated that their proportions, foliation, or sky reflections would give: Green, Yellow, and Blue Courts. Visitors can easily recognize the Green Court, with its vine roofing, or the Blue Court, with a splashing fountain that reflects sky and water off its travertine enclosure. The large Yellow Court is situated next to the Kimbell’s conservation studio.