Week 5

This week, my study of Frank Lloyd Wright’s arguably most famous and beloved building—Fallingwater—reinforced the risk involved in being a visionary—literally and figuratively going out on a limb. Wright’s innovative design and structural engineering of Fallingwater proved to be ahead of his time; fortunately, engineering advanced enough by 1995 to save the structure from collapsing under the weight of its own innovations. As critic Paul Goldberger noted, Fallingwater “summed up the 20th century and then thrust it forward still further,” and engineering fortunately caught up (Maddex, 50 Favorite Rooms by Frank Lloyd Wright).

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FALLINGWATER

Source: Fallingwater.org

Edgar and Liliane Kaufmann, the parents of one of Wright’s Taliesin students, hired Wright to build a weekend retreat for his family in Mill Run, Pennsylvania, in a remote wooded area outside of Pittsburgh. From the first time that he saw the Kaufmann’s favorite spot to picnic at the foot of a cascading waterfall in December 1934, Wright was enamored with the site. Despite being mesmerized by the musical grace of the waterfall spilling over the rocky ledges, Wright did not draft any plans until one summer morning in 1935 when Mr. Kaufmann called to say that he would be stopping by Wright’s studio in Taliesin to see the sketches. Incredibly, Wright quickly dashed off the design of what would become America’s most iconic home that morning. Apprentices polished the plans while Wright busied Mr. Kaufmann with a tour of Taliesin and leisurely meals (Thorne-Thomsen, Frank Lloyd Wright for Kids).   

Constructed from 1936 to 1939, Fallingwater sits precariously perched above the upper waterfalls of Bear Run stream, instead of predictably positioned at its base. In this way, the house would appear like a treehouse rooted in the rocky ledges of the waterfall, one with the land. Fallingwater is located far from civilization, nestled in a secluded valley in southwestern Pennsylvania. The surrounding mesophytic forest teeming with biological diversity provided a treasure trove of natural inspiration and materials for Wright to forage for inspiration. Wright did just that, quarrying stone from only 152 meters away and featuring native sandstone (“Key Works of Modern Architecture by Frank Lloyd Wright”).

Source: Architectural Digest

Fallingwater is a series of contrasts: vertical and horizontal, rough and smooth, gray and cream. Using stone exclusively for the house’s vertical piers and walls creates the sensation that the house is an extension of the waterfall. The cream-colored reinforced concrete cantilevers, however, float over the falls like foam, juxtaposing a manmade waterfall with its natural counterpart. The floors rise and recede as gracefully as the graduated levels of the waterfall (“Key Works of Modern Architecture by Frank Lloyd Wright”).

The piece de resistance of the house is its projection above the waterfalls by virtue of Wright’s incorporation of cantilevers. A popular element of Wright’s repertoire, a cantilever is a load-bearing horizontal beam that projects outward but is supported on only one end (“Key Works of Modern Architecture by Frank Lloyd Wright”).

Source: futurenostalgia.org

While the cantilevers almost seem to defy gravity, the entire house is grounded—literally and figuratively—by the towering sandstone chimney. The home is like a tree emerging from the rocks; its chimney functions as the trunk of the tree of the building; cantilevered terraces mimic branches. The first-floor cantilevered terrace spans a remarkable 18 feet over the waterfall (Lind, The Wright Style).

Source: Home-designing.com

Wright’s quest to bring the outside inside informs the construction of cantilevers. Terraces continue from the outside inside the house, only divided by plate glass windows and doors. Likewise, the same materials used on the outside of the building line the interior floor and walls, creating a unity of design. Moss grows up the walls, the cantilevers yield to the trees—marrying land and building (“Key Works of Modern Architecture by Frank Lloyd Wright”).

Source: Huffington Post

The synergy is sublime: rough flagstone paves the interior floors, waxed to create a shine reminiscent of the wet boulders in the river below. The most poignant example of Fallingwater’s connection to the environment, however, is the singular non-waxed boulder projecting into the house. Thus, the site’s most pronounced boulder anchors the home’s foundation. It was also the very boulder that Wright’s clients—Edgar and Liliane Kaufmann—had enjoyed as a frequent picnic spot, increasing its significance. Once again, Wright incorporated the four elements into the hearth (“Key Works of Modern Architecture by Frank Lloyd Wright”).

Source: StudyBlue.com

 Fallingwater, like most of Wright’s works, has an open floor plan. In fact, the ground floor is almost entirely a multipurpose family room, measuring 15 meters by 11 meters (“Key Works of Modern Architecture by Frank Lloyd Wright”). This room radiates under the golden light supplied by the large light screen in the ceiling; furniture hugs the room’s edges; cantilevering couches and tables continue the exterior theme (Maddex, 50 Favorite Rooms by Frank Lloyd Wright).

Source: Huffington Post

Moreover, the building itself spirals out like a pinwheel, with the conversation areas, a study-library space, and dining area jutting out or overlapping the open center, creating movement that echoes the flowing stream below (“Key Works of Modern Architecture by Frank Lloyd Wright”).

Fallingwater is not only a visual experience; it manipulates auditory and tactile senses to create a fuller connection between the landscape and the building. The sound of water reverberates throughout the site, gradually amplifying as one travels down the hillside and culminating at the building. Likewise, Fallingwater invites tactile sensation through its stairs just above the water, allowing mist to spray on visitors as they walk inside (Moore, Water and Architecture).

Source: Huffington Post

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While Frank Lloyd Wright’s Fallingwater may be a masterpiece of design, its engineering proved problematic. The massive cantilevers jutting over the water were too long to stay straight under the pressure of gravity and their own weights. Fearful that Fallingwater would fall down, the Kaufmanns hired an engineer to evaluate the structure in 1937. The engineer discovered that the structure indeed would eventually collapse, suggesting that props be placed below the cantilever on the first floor to provide support (Moore, Water and Architecture).

But Wright refused to change his plans (Moore, Water and Architecture). However, a contractor hired by Mr. Kaufmann cited that the main problem with the building was the limited number of reinforcing bars in the concrete. In fact, immediately after construction, upon removing the formwork, the cantilevers instantly deflected 1.75”—much greater than the normal expected deflection. Alas, the engineer who designed the girder—much to his embarrassment—realized that he forgot to put in the negative reinforcing, causing the steel to elongate and exceed its yield limit (Meek, “Fallingwater: Restoration and Structural Reinforcement”). A surveyor continued to monitor the deflections regularly.

Thus, by 1994, the four fifteen-foot-long concrete beams supporting the living room and other cantilevered terraces buckled under the weight of the house, deflecting four to seven inches out of their original positions. This pronounced deflection cracked the beams and stretched the steel bars in the reinforced concrete (The Architecture Handbook). Even worse, the sinking of the beams was accelerating because the second floor cantilever transferred its load to the first floor—something which Frank Lloyd Wright did not anticipate (Meek, “Fallingwater: Restoration and Structural Reinforcement”). For a while, it looked as though Fallingwater was doomed to collapse into the stream (The Architecture Handbook).

Source: misfitsarchitecture.com

Modern engineering, however, has supplied a remedy to steady Fallingwater while keeping it aesthetically intact. Computer modeling provided a non-invasive way to find the cause of the deflection and suggest a remedy. In 1995, the structural engineering company Robert Silman Associates decided to use a technique called post-tensioning, a process which secures a steel cable to both ends of a section of concrete before pulling taut the cable. In turn, the cable will compress the reinforced concrete so that it cannot bend (The Architecture Handbook).

Source: Wikispaces.com

After creating a temporary steel bracing in the stream to hold up the beams, construction workers pulled all 600 of the waxed flagstone tiles on the floor of the living room to expose the grid of concrete beams and joints underneath (The Architecture Handbook).

In the end, the cantilevers were not able to be raised back to their original position because it would have cracked the already firmly-set structure. Even so, the mere ¾ inch it did manage to rise was enough to save Fallingwater from falling into the water (The Architecture Handbook).

In retrospect, the flaws of Fallingwater enhance rather than detract from its appeal. Like the Liberty Bell or the Leaning Tower of Pisa, its problems only add another layer of patina, polishing the iconic image of Fallingwater. Wright’s thinking proved, once again, to be ahead of his time.

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Consequently, Wright’s innovation—cantilevers projecting out of rocks over water—spurred ensuing engineering innovations—post-tensioning repair. Seizing upon Fallingwater as an example of how integral engineering is to architecture, I decided to devise lesson plans to teach students the elementary principles of physics in architecture. 

My sketch of Fallingwater

Students from K-4 can gain familiarity with the structural elements of architecture by finding example photos from the internet or their town of the following: column, beam, cantilever, truss, arch, vault, and dome. The more unusual, the better.

Students from 5-8 can expand upon this knowledge and also consider the advantages and disadvantages of the five construction materials—wood, stone, brick, steel, reinforced concrete—and select the type of material most conducive for an array of structures—skyscraper, beach house, snowy mountain retreat, desert abode, etc.

For high-school students, my lesson plan will examine the basics of the physics behind cantilevers. As Fallingwater’s almost fatal fate reinforces, structural design depends on sound physics. To begin, I will introduce students to reinforced concrete—an inexpensive and flexible material used extensively by Frank Lloyd Wright—as a real-world application of the physics of architecture.

Normal concrete is strong under compressive forces, rendering it suitable for constructing vertical, load-bearing pillars. Concrete, however, is extremely weak under tension forces. Thus, it is a poor material for building horizontal beams or cantilevers, which experience both tension and compression forces (revisionworld.com).

Therefore, Frank Lloyd Wright could not use simple concrete in his construction of Fallingwater’s cantilevers. He had to turn to reinforced concrete.

Source: delanceyplace.com

By casting concrete around steel bars, the reinforced concrete can withstand tensile forces because tension is released as the concrete dries, shrinking the steel and compressing the concrete (revisionworld.com).

Wright constructed his gravity-defying cantilevers from reinforced concrete. A cantilever is “a beam that projects out and is supported only at one end,” according to The Architecture Handbook. Like all levers, such as a seesaw, the cantilever has a fulcrum (the point where the beam is supported), however, it is at the end of the lever instead of the middle (The Architecture Handbook).

Since cantilevers are only supported at one end, when a load is placed on top, the cantilever bends downwards slightly. This bending is called deflection.

To see this for yourself, stretch out your arm horizontally in front of you. This acts as a makeshift cantilever. Holding something heavy causes your arm to bend downward.

One of the problems with Fallingwater’s cantilevers is their length. Because the length of the cantilever varies inversely with its strength, the longer the cantilever is, the less it can hold, and thus the more it deflects.

Cantilevers have both tension and compression forces acting on them. Tension forces stretch the cantilever, while compression forces shorten it. The top of the cantilever experiences tension forces; the bottom of the cantilever experiences compression forces (The Architecture Handbook).

The load is supported by tension forces. The bending of the cantilever redistributes the force of the load up through compression. It then travels down the wall to the foundation of the building (ESF Academics).

If the beam bends too much under the weight of the load, you have to redistribute the load by attaching a cable from the end of the cantilever to the wall to move tension upwards. However, if the wall is not strong enough, then the compression will force the beam into the wall, damaging it (ESF Academics).

Hopefully, the lesson will impress upon students that architects are problem-solvers; their only limit is their imagination—and gravity!