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October 2005ARCHITECTURE <CULTURE >DESIGN

An early mock-up of Frank Gehry’s Experience MusicProject leans against the Zahner headquarters. To theright of it hang weathered sheet metal and test panelsfor the de Young museum, in San Francisco (photopage 3), where high salt content in the fog hastenedaging of the copper facade.

Photography by Mike Sinclair for Metropolis

On a glaringly bright June afternoon in Kansas City, Ifind myself standing outside a factory building admir-ing the effects of the Missouri climate on panels of per-forated copper. “When we were constructing this we hada severe ice storm in Kansas City,” says my tour guide,Paul Martin, a mechanical engineer who had helped designthe panels. “After it melted away it had the most spectac-ular purples.” He points to the verdigris streaking in thecinnamon-colored surface. “The way water falls down cop-per…there’s no way to replicate it.” Martin’s colleagueRoger A. Reed nods in reverent agreement: “It’s incrediblylovely.”

Now that mutable architecture has found expression inmutable metals, imaginative engineers are in demand. Thepanels in Kansas City were a test run for the distinctivefacade of the de Young museum, opening this month inSan Francisco’s Golden Gate Park. The architects,Herzog & de Meuron, have described it as ametamorphosing permeable skin intended tomimic the effect of light filtering through acanopy of leaves. It is the job of engineerslike Martin, at A. Zahner Company, a 108-

year-old architectural-metal firm in Kansas City, to turnsuch flighty metaphors into hard reality. Long known for itsclose association with Frank Gehry’s metallic meanderings,the company has consulted and produced skins, structures,and systems for an impressive list of architects, includingARO, Antoine Predock, Morphosis, Steven Holl, ZahaHadid, Rem Koolhaas, Tadao Ando, and Michael Graves. Inthe age of folded, textured, and curvaceous buildings, Zahnerhas become a clinic for twisting and treating metal.

Metal runs in the veins of this company. President and CEOBill Zahner—great-grandson of the company’s founder,Andrew Zahner—lives in a copper house in Kansas City. He

has written Architectural Metals, a 450-page textbook onthe forms and behaviors of metallic building materi-

als, and the 350-page sequel, Architectural MetalSurfaces, which bears as its epigraph a line fromthe Book of Malachi: “He will sit as a refinerand purifier of silver.” After joining the fami-

An obscure company is fast becoming thego-to fabricator for facade and

structural innovation.

BByy PPeetteerr HHaallll3 METROPOLIS October 2005

SHEET-METALMAGICIANS

ly business in 1978 with a civil engineering degree, Zahnerdecided to immerse himself in researching the properties ofthe stuff he’d grown up around, with a keen taste for itsartistic and architectural applications. When in 1986 unionrepresentatives of the Sheet Metal Workers InternationalAssociation (SMWIA) invited him to act as an intermediaryon its behalf for the design of a union anniversary exhibit,Zahner met the exhibition’s designer, the then lesser-knownFrank Gehry. The two men became friends, and in the ensu-ing years Gehry began to call on Zahner for advice on metalbehaviors and treatments. Their first big collaboration wasthe Weisman Art Museum’s new building, in Minneapolis,which opened in 1993.

With its cascading turrets in beaten and brushed stainlesssteel mimicking the rippling Mississippi below, the museumwas put together as one might expect from a sheet-metalshop: the flat sheets were cut and finished in the factory, and

A. Zahner Company has worked with an impressive listof architects, including Gehry,Koolhaas, Holl, and Hadid.

Top row, from left: a metalscreen–lined catwalk in the towerof the de Young museum; twodetails of exterior copper wallpanels. Right: looking outthrough the tower’s perforatedscreen; three details of weath-ered PVC-coated test panels.Below: the ceiling in the children’s courtyard; and light patterns cast during construction.

Zahner was asked to replicate the effect oflight flickering through a canopy of leaves.Abstracted photographs of tree canopieswere superimposed onto each elevation ofthe de Young tower (left). The dark purpleand pink regions correspond to areas on thefacade where light apertures—circular perfo-rations in the sheet metal—are wider indiameter and densely spaced (detail above)to allow more light to pass through.

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METROPOLIS October 2005

AVL turns an old campar into La Bais-ô-Drôma, a “bachalor machi-na” for pursuing axaggarataddasiras. A sculptura of baar cratasand concrata tilas, bottom laft,axploras proportion through tha

Left: an early mock-up of perforated PVC-coat-ed copper facade remains on the corner of theZahner headquarters (left). Below: a view of thede Young tower’s screen, now brownish fromweathering. Bottom: looking down past thetower’s torquing floor slabs.

5 METROPOLIS October 2005

PAST PROJECTSInsets, from top: Gehry’s WeismanArt Museum, in Minneapolis; hisExperience Music Project, in Seattle;and the Morphosis-designed WayneL. Morse Federal Courthouse inEugene, Oregon.

BEHIND THE SCENESClockwise from top left: sheet-metaljourneymen Jeff Dowell and RickBelew riveting a panel for Gehry;journeyman Kerry Butler weldingpieces of the courthouse; and RogerA. Reed, Shannon Cole, Mike Gekas,and Lesly Lamour at work in the engi-neering conference room.

A. Zahnerattracts a certain kind ofworker; asRoger A. Reedputs it, “Peoplewho find theunstable desir-able. If theywanted to dothe same thingevery day,

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6METROPOLIS October 2005

applied like shingles to the surface of the brick building onthe site. Under the skin was a fairly conventional structure.But when Gehry’s office landed the Experience MusicProject (EMP), in Seattle, it came to Zahner with a biggerchallenge: the building’s voluptuous skin was a structuralelement, the curving steel, pipes, and tubes forming a kindof exoskeleton. Such 3-D surfaces—derived from modelingcapabilities of computer-aided design tools newly importedfrom the auto and aerospace industries

—suggested three-dimensional prefabrication. Zahnerrealized it needed to rethink its whole design, production,and fabrication process, and make a substantial investmentin computing power. “That project completely changed thiscompany,” Zahner vice president of engineering TonyBirchler says. “We bought two Silicon Graphics Octanes at$25,000 a piece. Before that it was two guys drafting. WhenGehry hired us to develop the skin we had no idea how wewere going to do it. Fortunately the owner was committed to

Sections of Gehry Partners’ Ohr-O’Keefe Museum of Art in the Zahnerlot (top); installation instructions arehandwritten onto one of the panels(bottom). Inset: a rendering of the museum, now under construction.

7 METROPOLIS October 2005

the project and wanted to see it through.” He adds, with anod to the deep pockets of EMP patron Paul Allen, “We likeworking with billionaires.”

Zahner’s engineers came up with a modular system thathas since been refined and dubbed ZEPPS, for ZahnerEngineered Profile Panel System. (“We didn’t help themwith the name,” Gehry partner George Metzger quips.) Itsbasic building block is an arcing D-shaped bar of extrudedaluminum and flat steel. Several of these together form arib-cage structure for building three-dimensional panels ofalmost any shape or size. Tubed steel jigs are cut to hold upthe panels in three-dimensional space for assembly, and pan-els are stamped with a code indicating their position in afacade. These prefabricated partsare shipped to the job site in largecontainers atop flatbed trucks.“It works a little bit like a model-airplane kit,” Metzger says.“Zahner’s computer system willgo through the design automati-cally and organize all the parts tocreate a shape. The cutting pat-terns get sent over to a computersystem that cuts the shapes. Allthe shapes come in a box num-bered, and as long as they fit thenumbered parts in the rightplaces there’s very little measur-ing. You get a unique prefabricated shape that comes in abox.”

The company’s factory has an eerily quiet air when I visit,with a summer lull in projects brought about partly by theunexpected delay in construction of Moshe Safdie’s KansasCity Ballet project following a planning snafu. Three work-ers assemble panels for the Gehry-designed Ohr-O’Keefe artmuseum, in Biloxi, Mississippi, and the calm is occasionallybroken by the crash of metal falling from a fierce-lookingshear. Sheet-metal machinery looks fairly standard—brake,punch press, tube bender—but there are hints that this isnot a conventional factory floor. Machines are on wheels tomaintain flexibility according to job requirements, and com-puter monitors sit next to them. A vintage contraptioncalled a Campbell “nibbling” machine has been customizedby Zahner to pummel indentations in metal sheets accordingto data-fed instruction. On the walls and lying around onshelves and surfaces are zinc and copper panels, each bear-ing signs of having undergone tests for different patternsand patinas. Outside, the boxy 1980s structure has becomea palimpsest of experimental building skins, the originalweathering steel skin in turn covered by copper panels forthe de Young and others from various Gehry projects. “Itfeels like one of those insects that collects shells on its back,”Bill Zahner says of his building headquarters. “We haven’thad any neighbors complain yet.”

Zahner, who just turned 50, is the eldest of the four sib-lings, who work at the family business. Jo-Ann Mendenhallis chief problem solver, as Bill puts it, and the youngest,

Tom—though educated with a degree in hydrogeology—joined the firm as project manager for the EMP. (He current-ly handles special projects and enthuses about surface finish-es in an even more insouciant way than his elder brother.)The second youngest brother, Robert, is vice president incharge of engineering and labor relations. Although thebusiness has been unionized for more than a century and ison good terms with its local chapter, he admits that there issome effort involved in negotiating with a tradition-boundtrade association. Zahner’s post-EMP three-dimensionalway of working is anything but traditional. One companyengineer joked that prospective employees have to take adrug test before they are hired—if they test positive they

can work there. The place alsoattracts a certain kind of worker;as Reed puts it, “People who findthe unstable desirable. If theywanted to do the same thingevery day, they’d work at Ford.”

Developing a satisfactorymethod for fabricating the deYoung facade took the best partof a year. Using a series ofabstracted photographs of treesin the park as their source,Herzog & de Meuron architectsdeveloped a system with Zahnerfor replicating the dappled-light

effect with embossed concave and convex circles of elevenvarying depths and perforated holes of six varying diame-ters. Further factory tests using the nibbling machinerevealed that putting a flat bottom on the embossed circlesincreased the contrast at a distance. The challenge for thearchitects was that the design called for several hundred ofthese shapes in each of the 7,000 copper panels that madeup the building skin. “In the beginning the process wasalmost barbaric, with me sitting in front of a computer withAutoCAD manually placing different-size dots,” Herzog &de Meuron architect Chris Haas says. “After weeks of thatwe realized the amount of time it was consuming.” Zahnerpulled in a programmer, Eric Wilhelm, who wrote softwarein Perl that acted as a direct interface between architect andmachinery. Armed with this automated version, Haas couldadjust the contrast and porosity of the facade by changingthe pixel density in a Photoshop image. The Perl scriptwould then spit back a CAD file that could be the basis ofthe information read by the machines on the factory floor.“In the end they have tags for every panel in the buildingindicating the elevation and how far the panel was from theedge,” Haas says. “If any part is damaged, Zahner can plugin the file name and repunch it in an instant.”

Zahner has carved out a unique position in the UnitedStates with its emphasis on research and development, but itis not known as a low-cost option. According to Martin, thefirm more commonly finds itself competing against a budg-et than against another contractor for a job. Archi-tects whohave worked with the firm are quick to point out that a

Sheet-Metal Magicians

8

Zahner’s post-EMP three-dimensionalway of working is anything but tradi-tional. One company engineer jokedthat prospective employees have totake a drug test before they are hired—if they test positive they can workthere.

METROPOLIS October 2005

structural Zahner skin can eliminate the need and cost ofanother contractor designing steel profiles underneath. ButZahner fans are currently small in number. Unsurprisinglythe firm is now attempting to position itself as both a fabri-cation shop and engineering design consultancy so that it isnot left hanging for a job order after proposing how to buildit. (Occasionally Zahner has seen fabrication techniques itproposed in a bid taken to a different contractor.) This wayarchitects needing to figure out how to fabricate a complexsurface will bring their ideas to Zahner before they embarkon detailed models, avoiding unnecessary redesigns.

In an era in which pliant forms and organic-looking sur-faces are de rigueur, Zahner’s expertise must seem lessbespoke than it did ten years ago—and more of a necessarystage between conception and production. Morphosis fortu-itously encountered Zahner through its general contractorfor a courthouse project in Eugene, Oregon. The designincludes an “angel-hair” finish on its steel panels (a nowstandard Zahner innovation to reduce glare and add texture)and a number of sloping asymmetrical surfaces that posedtheir own fabrication challenges. Information and de-signswere traded back and forth between Zahner and Morphosisvia digital files and physical 3-D printer models (miniaturestarch-based versions of the buildings), a paperless processhinting at the possibility that 2-D plans may soon be obso-lete. “More and more we find subcontractors are interestedin 3-D models because they can more easily visualize theproject and lay everything out,” Morphosis architect MariaGuest says. “Paper is still important, but as a map to navi-gate the design, 3-D models make it a million times easierand much more fluid.”

Out in Zahner’s yard computer models materialize intogleaming silver modules. In June the prefabricated panels ofthe Ohr-O’Keefe museum were stacking up on carts readyfor shipping. Each is coded, stamped, and marked, withhandwritten special instructions on the reverse in a perma-nent marker. Bill Zahner argues that in five years the firm’smodular assembly system will look nothing like the metal

parts stacked outside. “It’s evolving all the time, and we’repushing it. Look at the beam-and-column approach: it’s notthe most efficient way of doing three dimensions. The inter-esting point is where it goes from here.”

It is easy to see why so many of Gehry’s rivals have turnedto this Kansas City shop for help. The firm is clearly invigor-ated by its own research, according to Herzog & de Meuron’sLoughnan: “Bill Zahner loves his metal. He has a passion forit, and when somebody has a passion it tends to drive thewhole process in a positive way.” His ongoing researchincludes an in-house investigation of methods to embed oxi-dized metal in glass and an external project led by GeneralElectric to develop a laser-forming process for creating metalparts, funded by a National Institute of Standards andTechnology grant.

For a day spent bombarded by technical information, myreceding impression of A. Zahner Company was of an enthu-siastic group of engineers whose zeal for systems and mate-rials was quite distinct from many architects’ carefully artic-ulated positions on finishes and processes. One is tempted tofind in Bill Zahner’s embrace of change a reflection of theunpredictable metals he works with. Metal, it seems, is afickle fellow, changing literally with the wind. Herzog & deMeuron had expected its gleaming penny-colored de Youngfinish to progressively fade from a bright copper to a cinna-mon color and eventually assume a rich green patina thatwould blend with its park surroundings over a decade ormore. But in foggy San Francisco there was a little too muchsalt in the air, and a few weeks after the facade was erecteddark black blotches began appearing across the perforatedforest of metal. Museum trustees freaked out. “A trusteeasked how we could avoid this ‘adolescent period,’” BillZahner recalls. “I said, ‘You’re just going to have to wait.’”Happily a year before opening day the copper had obliging-ly mellowed to a more palatable all-over tan.

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Reprinted with permission from Metropolis Magazine, October 2005. For web posting only. Commercial or bulk printing prohibit-ed. For hard copy reprints, call The Reprint Dept. at 800-259-0470

Sheet-Metal Magicians