This article was originally published on April 14, 2014. To read the stories behind other celebrated architecture projects, visit our AD Classics section.
With the design for Los Manantiales, Felix Candela’s experimental form finding gave rise to an efficient, elegant, and enduring work of structural art. Comprised of four intersecting hypars, a strikingly thin roof surface creates a dramatic dining space. Built as Candela was establishing an international reputation as the foremost shell building, he demonstrated to the world his masterful combination of artistry and technical virtuoso.
Los Manantiales was created as Candela’s mastery thin-shell concrete construction was solidifying. Initially conceived for another client on a different site, the structure found realization as a replacement for a wooden restaurant alongside a floating gardens filled canal in the Xochimilco area of Mexico City.
Candela’s fascination with thin-shell structures was piqued during his studies at La Escuela de Arquitectura de Madrid. An extraordinary athlete and facile student, he supplemented his formal training with a independent reading on techniques for analysis of form.
His academic career was interrupted when the Spanish Civil War erupted, but his experiences restoring buildings for military use gave him first hand exposure to construction techniques. Candela’s later practice merged theoretical studies with careful consideration of building processes.
During the war Candela was imprisoned, but given the opportunity to emigrate to Mexico as an exile. There, concrete was an increasingly popular building material that represented modernization, efficiency, and a break from the past for a people who had just gotten through their own political upheaval.
Candela began building thin shell structures not for clients but as full scale experiments. Although he constructed some cylindrical forms, Candela working intensely with hyperbolic paraboloids, or hypars. Eschewing the trend toward reliance on complex mathematics, Candela developed forms where stresses could be determined with simple equations. A form Candela called “umbrellas,” created by joining four straight edge hypars, were an efficient way to cover large spaces such as markets and warehouses. His construction of the Cosmic Rays Laboratory utilized hypars to add stiffness and minimize material thickness, and received international acclaim.
The iconic form of Los Manantiales was derived through continued geometric investigation. Called “La Flor” (The Flower) by townspeople, a continuous interior space is enclosed by an singular sculptural surface. Light spills through the glass apertures that infill each vault, highlighting the roof form.
The roof is a circular array of four curved-edge hypar saddles that intersect at the center point, resulting in an eight-sided groined vault. The plan is radially symmetric with a maximum diameter of 139 feet. Groins spanning 106 feet between supports. Trimmed at the perimeter to form a canted parabolic overhang, the shell simultaneously rises up and out at each undulation. The force paths from these overhangs act in the opposite direction from forces along the arched groin, reducing outward thrust.
The largest membrane forces are carried along the intersections between the forms, called the groins. This areas are thickened by creating hidden steel reinforced “V” beams. The rest of the structure has minimal reinforcing to address creep and temperature effects, but essentially works entirely in compression. The symmetrical plan and innovative use of “V” beams allows edges free of stiffening beams, revealing the radical thickness of the 4cm (1 ½”) shell.
A section through Los Manantiales shows the parabolic arch along the groins and the inverted arch through the highpoint of each vault.
Narrow boards were used as formwork, following the straight-line generator that forms the hypar surface. Steel reinforcing and a layer of cement grout (to create a smooth inner surface) underlie concrete applied one bucket at a time by laborers.
Candela inverted his umbrella form for the footings, a material saving strategy to distribute the weight of the structure onto the poor quality soil of Mexico City. Five 1” diameter steel tie-bars link adjacent footings and resist lateral thrust. Candela softened the form at the intersection of the hypars, creating a curve and giving the appearance of a continuous form.
Los Manantiales is still operated as a restaurant today, but the picturesque setting present at the time of construction has changed. Additional structures and a fence block views of the structure. Piecemeal modifications, such as the application of a red waterproofing layer and modifications at the supports blunt the clarity of form initially present. Despite this, the shell is still structurally intact and a majestic presence in Xochimilco.
Although not Candela’s first groin vault structure, it was the first to receive international attention. The form of Los Manantiales reappears in a later work by Candela in Spain, and has been emulated several times by other designers in locales such as Potsdam and Stuttgart. Candela’s work continues to inspire contemporary designers such as Santiago Calatrava.
For more information, visit the site created for Princeton’s 2008 exhibit on Candela here.
Burger, Noah and Billington, David P. “Felix Candela, Elegance and Endurance: an examination of the Xochmilco Shell.” Journal of the International Association for Shell and Spatial Structures: IASS. Volume 27 (2006) No. 3, December n. 152, pgs 271-278.
Guthrie, Jill, editor. Felix Candela: Engineer, Building, Structural Artist. Princeton, NJ: Princeton University Art Museum, 2008.
“Recent work of Mexico’s Felix Candela.” Progressive Architecture 40 (1959): 132-141.