Wednesday, June 17, 2009

Felix Candela and Restaurant Los Manatiales

Felix Candela and Restaurant Los Manatiales, Xochimilco, Mexico
by Nanette South Clark

A Brief History of Felix Candela:
(Photo from Structurae)

Felix Candela Outerino, known best simply as Felix Candela, was born in Madrid, Spain in 1910. According to Wikipedia, in 1927 Can­dela en­rolled in La Es­cuela Su­pe­rior de Ar­qui­tec­tura (Madrid Su­pe­rior Tech­ni­cal School of Architecture), grad­u­at­ing in 1935. Can­dela then trav­eled to Ger­many to fur­ther study ar­chi­tec­ture.

The Span­ish Civil War be­gan in 1936, and Can­dela re­turned to Spain to fight. Can­dela be­came a Cap­tain of En­gi­neers for the Span­ish re­pub­lic. While par­tic­i­pat­ing in the civil war, Can­dela was im­pris­oned in the Per­pig­nan Con­cen­tra­tion camp in Per­pig­nan, France un­til the end of the war in 1939. Can­dela fought against Franco; there­fore he could not stay in the new Spain as long as Franco was the head of state. Af­ter his name was se­lected with a few hun­dred other pris­on­ers, Can­dela was put onto a ship bound for Mex­ico, where he began his ca­reer.

Candela mar­ried Ela­dia Mar­tin when he moved to Mex­ico from Spain; there, they raised a fam­ily. In his early life, Fe­lix was ac­tive in sports, par­tic­u­larly rugby and skiing.

First working for others in Acapulco, he moved to Mexico city and set up his own practice, specializing in the design and construction of thin tensile concrete shells. Because this was a new way of building, Candela acted as architect, structural engineer, and contractor, even training the construction workers himself. He began building beautiful churches such as Medalla de la Virgen Milagrosa (1953-1955), Nuestra Senora de la Soledad Chapel (1955), and San Jose Obrero (1959), all in Mexico City, and the Open Chapel in Lomas de Cuernavaca (1958) (Encyclopedia of architectural and engineering feats, By Donald Langmead, Christine Garnaut, Page 304). Can­dela did most of his work in Mex­ico through­out the 1950s and into the late 60s. He was re­spon­si­ble for more than 300 works and 900 projects in this time pe­riod.

Many of Candela's larger projects were given to him by the Mex­i­can gov­ern­ment, such as the Cos­mic Rays Pavil­ion. In 1956, Mex­i­can Pres­i­dent Adolfo Ruiz Cortines said, "Nothing could be more se­ri­ous than to sit in the shade of the build­ings we are about to build.”

(Photo of Santiago Calatrava (left) and Felix Candela (right) from Gibson Design)

Candela worked very hard dur­ing his life time to prove the real na­ture and po­ten­tial re­in­forced con­crete had in struc­tural en­gi­neer­ing and earned the nickname, "the Shell Builder." He also looked to solve prob­lems by the sim­plest means pos­si­ble. In re­gard to shell de­sign, he tended to rely on the ge­o­met­ric prop­er­ties of the shell for anal­y­sis, in­stead of com­plex math­e­mat­i­cal means.

Can­dela eventually be­came a pro­fes­sor in Mex­ico, which is what he did for the re­main­der of his ca­reer. Félix Can­dela died at the age of 87 in 1997 in North Carolina.

Hyperbolic Paraboloids:
(Paraboloid sketch from

The Encyclopedia of architectural and engineering feats asserts, "The roofs and sometimes the walls of Candela's shell structures are noteworthy for their seamless concrete construction, often only 1.07 inches (4 centimeters) thick. Candela stated, 'It is the shape that matters.' He insisted that 'the shell must be stable and of a shape which permits an easy way to work. It should be as symmetrical as possible because this simplifies its behavior' (Faber 1963, 199). To this end, he frequently made use of the hyperbolic paraboloid, a form that made the construction of timber formwork easy because it is generated only from straight lines. The best example can be found in Los Manantiales Restaurant of 1958 in Xochimilco near Mexico City; the thin concrete shell structure that encloses its radial plan is based on eight hyperbolic paraboloid segments. Critics have remarked that in Candela's work both design and structure have been sharpened to the finest edge, imparting 'a new dynamism' to architecture."

(Photo from flickr)

"Candela made his reputation with his designs for hyperbolic paraboloids (hypars), the thin concrete vaulted shells known for their unusual strength and flexibility. Instead of the more common longitudinal vault axes, Candela had worked out a system of diagonal directrixes that made it possible for the vaults to be both light and resistant. His vaults were not of precast concrete but of concrete mixed and poured on the spot over a temporary wooden support with wire mesh to hold the concrete in place (Twentieth-century art of Latin America, By Jacqueline Barnitz, page 181)."

From Wikipedia: The hyperbolic paraboloid (not to be confused with a hyperboloid) is a doubly ruled surface shaped like a saddle. In a suitable coordinate system, it can be represented by the equation

Hyperbolic paraboloidImage via Wikipedia
This is a hyperbolic paraboloid that opens up along the x-axis and down along the y-axis.

The hyperbolic paraboloid is a doubly ruled surface: it contains two families of mutually skew lines. The lines in each family are parallel to a common plane, but not to each other.

The surface generation of a hyperbolic paraboloid is formed by sweeping a convex parabola along a concave parabola or by sweeping a straight line over a straight path at one end and another straight path not parallel to the first. This differs from the generation of a conoid which is formed by moving a one end of a straight line along a curved path and the other along a straight path. The hyperboloid is also formed differently by rotating a straight line around a vertical axis.

Structural behaviors depend on the shape of the shell relative to the curvature. Shell roofs, have compression stresses following the convex curvature and the tension stresses follow the concave curvature.

The Pringles potato chip is a close approximation of a hyperbolic paraboloid.

Los Manantiales Restaurant:

In, Twentieth Century Architecture, page 220, Dennis Sharp says, "Candela's delightful octagonal shell resaurant replaced an earlier timber structure destroyed by fire. Called Los Manantiales (literally, 'The Springs'), it is virtually surrounded by water. The setting is beautiful, the building revolutionary."

(Photo from Auburn University)

According to Princeton University, "Candela’s stimulus for the form of Los Manantiales Restaurant in Xochimilco, Mexico City came from Colin Faber, who was working with Candela at Cubiertas Ala. Faber had made a rough sketch that somewhat resembled the final form of the restaurant; Candela liked the idea, so he took it and redesigned it into a more graceful shape."

The edges of Los Manantiales' shell are parabolic and free of any edge stiffeners. This exposes the shell's thinness. The shell of Los Manantiales is called a groined vault. Princeton University defines the groins as, "the valleys in the shell formed at the convergence of the intersecting hypars."

Princeton University describes the construction of Los Manantiales:

As was his practice, at Xochimilco Candela used V-beams for groin stiffening, which was not visible, either from the inside or the outside, thus adding a bit of mystery to the educated observer of shell behavior. The V-beams are reinforced with steel, while the rest of the shell has only nominal reinforcing, not for added strength, but to address temperature effects and other properties of the concrete material that can cause cracking.

At the supports, Candela anchored the V-beams into inverted umbrella footings, which cup the earth to prevent the shell from sinking into the soft Mexican soil. To resist lateral thrusts, he linked adjacent footings with steel tie-bars, thus allowing the umbrella footings to carry only vertical loads. Candela was pleased with the unique visual design of his support detail, where instead of a sharp V-shape, he formed it into a curve to give it continuity. He commented that this is “what makes [the shell] so graceful, the regularity and the proportion . . . it looks good and I like it."2

The form boards for construction followed the path of the straight-line generators that formed the hypar surface. With the form boards in place, and then the reinforcing steel laid on them the concrete could be cast by hand, one bucket at a time. When the concrete had hardened to sufficient strength, the scaffolding and form boards were removed. It is at this point that the shell comes alive and is seen in its purest, most refined form. Following the addition of architectural details (windows, doors, etc.), the structure remains the most prominent feature.

(Photo of scaffolding during construction of Los Manantiales Restaurant from Auburn University)

The Creator's Words:

"It may be said there are two basic criteria for a proper shell:

"The shell must be stable and of a shape which permits an easy way to work. It should be as symmetrical as possible because this simplifies its behaviour. Either interior groins (as in the restaurant in Xochimilco) or exterior edges should be able to send loads to points of support, or else there should be a continuous support along certain edges....

"A comparatively rapid, simple method must be found to calculate the membrane stresses. At the moment this seems possible only with the hypar shell, if by 'simple' one infers a procedure which mathematics, or specifically, in every case having to solve a system of differential equations to comply with previously selected boundary conditions."

— Felix Candela. from Colin Faber. Candela/The Shell Builder. p199.

(Photo of the construction of Los Manatiales restaurant as it neared completion in 1957 from Dorothy Candela)


Maria Garlock, David Billington, and Stanley Allen of Princeton University evaluated Restaurant Los Manatiales and reported their findings in, Building for the Future: Evaluating the Current Viability of
Thin Shell Concrete Structures
. The structure was analyzed using finite element computer models.

(Photo of Dorothy Candela, Maria Garlock, and David Billington from Princeton)

They also examined how Candela developed the form for his structures and how he analyzed them. They were able to evaluate such things by visiting the home of Mrs. Candela and finding documents such as an unpublished autobiography and transcripts of interviews.

Garlock, Billington, and Allen's analyses showed that the compressive stresses in Candela’s shells are well below the strength of concrete. "The tensile stresses are also typically below the tensile strength, but in any case Candela included reinforcing steel throughout for incidental stresses that may arise from creep, shrinkage, and temperature effects for instance. Such steel was more than sufficient for any tensile stresses that may develop."

(Photo of the interior of Restaurant Los Manatiales from flickr.)

They state further that, "Candela has written that 'The quality of a structural design is in inverse proportion with the amount of calculations necessary for its erection.' Candela used membrane theory, which he validated with simple calculations that he developed by reducing what appeared to be a complex form into something as simple as a cantilever (in the case of umbrellas) and three hinged arches (in the case of groined vaults). We found that in many cases these simple equations lead to the same design as complex nonlinear finite element solutions."

For further reading and analysis details, FELIX CANDELA, ELEGANCE AND ENDURANCE: AN EXAMINATION OF THE XOCHIMILCO SHELL, by Noah Burger and David P. Billington, is a more in-depth analysis of Restaurant Los Manatiales.


Félix Candela: Builder, Engineer, Structural Artist
April 2 - September 27, 2009


Félix Candela: Engineer, Builder, Structural Artist, is an exhibition devoted to the work of Spanish-born master builder and structural artist Félix Candela (1910-1997). Recognized as one of the great structural artists of the twentieth century, Candela designed and built innovative thin shell concrete roof structures, mostly in Mexico, using the hyperbolic paraboloid geometric form (hypar).

(Photo of Sylvester Black ’09 gluing the joints of the falsework for a model of Félix Candela’s Los Manatiales restaurant in Xochimilco, Mexico City from Princeton.)

Also on view are animations of the development of the structures, original design drawings, carefully crafted scale models of buildings under construction and after completion designed and built by Princeton University graduate and undergraduate students, photographs, and a slide show. Visitors will be able to see evidence of the thinness of the shells, imprints of straight-line form boards that hint at the construction process and elegance of shape. Candela’s personal notebooks and sketchpads will provide insight into his education, the traditions that helped develop his ideas, and how he thought about his designs and their more profound meaning.
(Photo of the completed model of Candela’s Los Manatiales restaurant from Princeton.)

This exhibition was curated by Maria E. Moreyra Garlock, Assistant Professor of Civil and Environmental Engineering, and David P. Billington, Gordon Y. S. Wu Professor of Engineering, both of Princeton University. The exhibition was organized by the Princeton University Art Museum and the Princeton University Department of Civil and Environmental Engineering.

Candela Quotes:

(Photo of Felix Candela from Urbipedia.)

"It is forgotten that mathematics is only a means, ... but that the rigidity and precision of mathematical reasoning can not guarantee us the exactness of the results of its application because we must always begin from a supposed arbitrary original." (Felix Candela, "Toward a New Philosophy of Structures," Student Publications of the College of Design, North Carolina State (1954): Vol. 5 # 3)

"I sometimes allow myself to fancy that progress of the structural technique could have taken place by means of the natural evolution of intuitive and experimental methods employed with such amazing success in the Middle Ages and the Renaissance. Perhaps such a development, …..could have led to a better use of the properties of the materials, for the problem might have been approached more openly, without the blind faith that it may be solved by mathematical procedures. The most fitting forms are not, as a general rule, easy to investigate…….,; hence their use has been neglected in favor of less appropriate solutions that are easier to analyze." (Felix Candela, "The Shell as a Space Encloser," Proceeding, Conference on Thin Concrete Shell, MIT (June 1954))

(Photo of Felix Candela from

" I am a practical man, because I have no choice. I must be practical in order to survive and therefore I choose only to build structures that I can calculate myself. Of course there are many opinions regarding the question of calculation, and it is a highly personal problem how far one is to calculate. Myself, I believe that if the structure stands up with the simple calculations I make, that is enough." (Felix Candela, "Shell Structure Development", The Canadian Architect, (Jan 1967): Vol.12, 33-40)

"Nature's most usual way of performing this function is by means of either rigid shells or elastic membranes. Since this second form can hardly be considered as architectonic, "shell" remains a synonym of space enclosure and the title of this essay(Shell as Space Encloser) appears to be somewhat redundant." (Felix Candela, "The Shell as a Space Encloser," Proceedings, Conference on Thin Concrete Shell, MIT (June 1954))

"The essential function of architecture is to limit a volume from the non-architectural extent of open space, so that within it man may develop his living activities undisturbed by weather inclemencies. The unique feature which distinguishes architecture from other plastic arts is precisely this dealing with internal hollow space." (Felix Candela, "The Shell as a Space Encloser," Proceedings, Conference on Thin Concrete Shell, MIT (June 1954))

(Photo of Felix Candela from Toto Ltd.)

"This inquiry has never been more pertinent than now when a monolithic material which can be cast in any desired form has become of common use in building. Reinforced concrete is not only very akin to the stuff of natural shells, but it has even the advantage of being able to withstand substantial stresses. These properties of continuity and tensile strength of reinforced concrete place before us a unique opportunity to emulate the distinctive economy of material of natural methods of enclosing space." (Felix Candela, "The Shell as a Space Encloser," Proceedings, Conference on Thin Concrete Shell, MIT (June 1954))

"Now I am asked to do other things about which I don't know anything. I am being asked to cover very large areas because it is said, 'This man does beautiful small shells'; so they ask me to build a 500 ft. shell. Of course I can't do it, I have to begin to think again and this is a terrible problem because thinking is one of the most painful tasks that one can have. It is incredible the amount of work that people do in order to avoid thinking." (Felix Candela, "Shell Structure Development", The Canadian Architect, (Jan 1967): Vol.12, 33-40)

(Photo of Felix Candela from monoculartimes.)

"On the other hand, in times of plenty there is a tendency toward mental slothfulness. We have already every conceivable kind of material, and their properties are continually improving. Why should we trouble to look for new forms or worry about design when it is so much easier to demand just a little more resistance of a certain material." (Felix Candela, "Toward a New Structure," Architectural Forum, (1956))

"Quoting the older aphorism 'Function creates the organ' (which curiously enough links the words that name both outstanding trends of the modern movement) a well known postulate of functionalism states that 'Form follow function'. But architecture is not made with words, and in the practical application of both sentences it is often forgotten that the creation of new forms can only take place by means of structure." (Felix Candela, "The Shell as a Space Encloser," Proceedings, Conference on Thin Concrete Shell, MIT (June 1954)

"If a rebel was able to produce such beautiful and sound structures there could be nothing wrong with becoming a rebel myself." (Colin Faber, Candela/ The Shell Builder (Reinhold Publishing Corporation, 1963))


Candela's draw­ings, cor­re­spon­dence, per­sonal and pro­fes­sional pa­pers, and writ­ings are held in the per­ma­nent col­lec­tion of the Department of Draw­ings & Archives in the Avery Ar­chi­tec­tural and Fine Arts Library at Columbia University in New York City.

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