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Digitized by the Internet Archive in 2012 with funding from LYRASIS Members and Sloan Foundation http://archive.org/details/maintenancerepair27wait PRESERVATION Z/ f BRIEFS The Maintenance and Re/pair of Architectural Cast Iron u^*s,TY 0F GE0RG*A John G. Waite, AIA MAY 1 2 19' Historical Overview by Margot Gayle U.S. Department of the Interior In Cooperation with the National Park Service Cultural Resources New York LandmarksConservancy Preservation Assistance The preservation ofcast-iron architectural elements, James Bogardus. From 1840 on, Bogardus extolled its including entire facades, has gained increasing attention in virtues ofstrength, structural stability, durability, relative recent years as commercial districts are recognized for their lightness, ability tobe cast in almost any shapeand, above historic significanceand revitalized. This Brief provides all, the fire-resistantqualities so sought after in an ageof general guidance on approaches to the preservation and serious urban conflagrations. He also stressed that the restoration ofhistoric cast iron. foundry casting processes, by which cast iron was made into building elements, were thoroughly compatible with Castiron played a preeminent role in the industrial the new concepts ofprefabrication, mass production, and development ofour country during the 19th century. Cast- iron machinery filled America's factories and made possible use of identical interchangeable parts. the growth ofrailroad transportation. Cast iron was used extensively in ourcities for water systems and street lighting. As an architectural metal, it made possible bold new advances in architectural designs and building technology, while providing a richness in ornamentation (Fig. 1). This age-old metal, an iron alloy with a high carbon content, had been too costly to make in large quantities until the mid-18th century, when new furnace technology in England made it more economical for use in construction. Known for its great strength in compression, cast iron in the form of slender, non-flammable pillars, was introduced in the 1790s in English cotton mills, where fires wereendemic. In the United States, similar thin columns were first employed in the 1820s in theaters and churches to support balconies. By the mid-1820s, one-story iron storefronts were being advertised in New York City. Daniel Badger, the Boston foundryman who later moved to New York, asserted that in 1842 he fabricated and installed the first rolling iron shutters for iron storefronts, which provided protection against theft and external fire. In the years ahead, and into the 1920s, the practical cast-iron storefront would become a favorite in towns and cities from coast to coast. Not only did it help support the load of the upper floors,but it provided large show windows for thedisplay ofwares and allowed natural light to flood the interiors ofthe shops. Most importantly, cast-iron storefronts were inexpensive to Fig. 1. The Haughzvout Building in New YorkCityisan excellent assemble, requiring little on-site labor. exampleofthequalityandcharacterofmass-producedcast-iron architecture. Once woodpatterns were made,any numberofelements A tireless advocate for the use ofcast iron in buildings was could becast,as was done witheach ofthese repetitive bays. Photo: an inventive New Yorker, the self-taught architect/engineer Nezv YorkCity Landmarks Preservation Commission. — In 1849 Bogarduscreated something uniquely American several ironfronts were begun in 1850: The Inquirer when he erected the first structure with self-supporting, Building, the BrockStores, and the Penn Mutual Building multi-storied exterior walls ofiron. Known as the Edgar (all three have been demolished). The St. Charles Hotel of Laing Stores, this corner row ofsmall four-story 1851 at 60 N. Third Street is the oldest ironfront in America. warehouses that looked like one building was constructed Framing with cast-iron columns and wrought-iron beams in lower Manhattan in only two months. Its rear, side, and and trusses was visible on a vast scale in the New York interior bearing walls were ofbrick; the floor framing Crystal Palace of 1853. consisted oftimber joists and girders. One of the cast-iron walls was load-bearing, supporting the wood floor joists. In the second half of the 19th century, the United States was The innovation was its two street facades ofself-supporting Tinheanusereaooifirtorneminencdoomumsereccioanlomaincdapnubdlitcerrbiutiolrdiailnggsroswptrhe.ad cast iron, consisting of multiples ofonly a few pieces rapidly, and hundreds ofiron-fronted buildings were Doric-style engaged columns, panels, sills, and plates, along with some applied ornaments (cover photo and Fig. 2). erected in cities acrossthe country from 1849 to beyond the turn of the century. Outstanding examples ofironfronts Each component of the facades had been cast individually exist in Baltimore, Galveston, Louisville, Milwaukee, New in a sand mold in a foundry, machined smooth, tested for Orleans, Philadelphia, Richmond, Rochester (N.Y.), and fit, and finally trundled on horse-drawn drays to the especially New York City where the SoHo Cast Iron building site. There they were hoisted into position, then Historic District alone has 139 iron-fronted buildings bolted togetherand fastened to the conventional structure of timber and brick with iron spikes and straps (Fig. 3). n(Faitgi.o1n)w.iRdeegrheatvteabbleye,nadleamrgoelipsrhoepdoritniodnoowfnitroownfnronts The second iron-front building erected was a quantum leap redevelopment projects, especially since World War II. beyond the Laing Stores in size and complexity. Begun in April 1850 by Bogardus, with architect Robert Hatfield, the five-story Sun newspaper building in Baltimore was both ROOF (CONSTRUCTION NOTACCESSIBLE) cast-iron-fronted and cast-iron-framed. In Philadelphia, WOODEN JOIST IRON STRAP WINDOW CONSTRUCTION (NOT ORIGINAL) IRON COLUMN Ja WOODEN^ SPACER SILL- BOLT r PLAN OF COLUMN iron panel IRON PANEL FLOOR FLANGE BOLT / ig. I. The I dgnr Laing Stores Block in New )ork City wasdesigned WOODEN JOIST In/ James Bogardus. II was the first building constructed with facades ~ el self-supporting cast iron. This corner viewshows the Doric-style SECTION THROUGH WALL 1 .. .. ,/ S J engagedcolumns, panel--, and spandrel beams: the lossoj most of the originalornamental castingsgive it an austerelook. As part ojan urban renewamlproject\ the facades were—carefullydisassembledin 1971 Fig. 3. Section drawing through the wallofEdgar Laing Stores showing I itei re i lion inanotherlocation only tohave its iron parts how thecast-iron facadecomponents wereanchored to the wood floot and stolen joi scrap. Photo: Jack E. Boucher, HABS Collection. roofframing members. Drawing: John G. Waile. HABS Collection. Fig. 5. The Slatter Family Tomb in Mobile, Alabama,consistingofa cast-iron mausoleum and fence,exhibits thewide rangeofuses ofthe material in the 19th century. Photo: Jack E. Boucher, HABS Collection. Shakspeare (sic) Foundry, and Miltenberger in New Orleans; Winslow Brothers in Chicago; and James McKinney in Albany, N.Y. Cast iron was the metal ofchoice throughout the second halfofthe 19th century. Not only was it a fire-resistant Fig. 4. The 1904grandstairwayofthe former Frear'sdepartment material in a period of major urban fires, butalso large storein Troy, N.Y. ions constructedofeast iron,as was theframeof facades could be produced with cast iron at less cost than theski/lightabove. Someornamental wrought iron wasalso comparable stone fronts, and iron buildings could be employed. Tins useofiron was typical in majorcommercial buildings erected with speed and efficiency. The largest standing constructed throughout the United States. Courtesy: Rensselaer example of framing with cast-iron columnsand wrought- CountyHistorical Society. iron beams isChicago's sixteen-story Manhattan Building, the world's tallestskyscraper when built in 1890by William In addition to these exterior uses, many public buildings LeBaronJenney. By this time, however, steel wasbecoming display magnificentexposed interior ironwork, at once availablenationally, and was structurally more versatile ornamental and structural (Fig. 4). Remarkable examples and cost-competitive. Its increased use is one reason why have survived across the country, including the Peabody building with cast iron diminished around the turn of the Library in Baltimore; theOld Executive Office Building in century after having been so eagerly adopted only fifty Washington, D.C.; the Bradbury Building in Los Angeles; years before. Nonetheless, cast iron continued to be used in the'former Louisiana StateCapitol; the formerCity Hall in substantial quantities for many other structural and Richmond; Tweed Courthouse in New York; and the state ornamental purposes well into the20th centviry: storefronts; capitols ofCalifornia, Georgia, Michigan, Tennessee, and marquees; bays and large window frames for steel-framed, Texas. And it is iron, ofcourse, that forms the great dome masonry-clad buildings; and street and landscape of the United States Capitol, completed during the Civil furnishings, including subway kiosks. War. Ornamental cast iron was a popular material in the landscape as well, appearing as fences, fountains with The 19th century left us with a rich heritage ofnew building statuary, lampposts, furniture, urns, gazebos, gates, and methods, especially construction on an altogether new scale enclosures forcemetery plots (Fig. 5). With such that was madepossible by the use ofmetals. Ofthese, cast widespread demand, many American foundries that had iron was the pioneer, although its period of intensive use Now been casting machine parts, bank safes, iron pipe, or lasted buta halfcentury. the surviving legacy ofcast- cookstoves added architectural iron departments (Fig. 6). iron architecture, much of which continues tobe threatened, Thesecalled for patternmakers with sophisticated design merits renewed appreciation and appropriate preservation capabilities, as well as knowledgeofmetal shrinkage and and restoration treatments. other technical aspectsofcasting. Major companies included the Hayward Bartlett Co. in Baltimore;James L. Jackson, Cornell Brothers,J. L. Mott, and Daniel D. Badger's Architectural Iron Works in Manhattan; Hecla Ironworks in Brooklyn; Wood & Perot of Philadelphia; Leeds & Co., the Maintenance and Repair What is Cast Iron? Many of the maintenance and repair techniques described in the Brief, particularly those relating to cleaning and Cast iron is an alloy with a high carbon content (at painting, are potentially dangerous and should be carried least 1.7 r and usually 3.0 to 3.7%) that makes it more out only by experienced and qualified workmen using resistant to corrosion than either wrought iron or steel. protective equipment suitable to the task. In all but the aInmoauddnittsioonftsoilciacornb,onsu,lcfuars,t imraonngaconnetsaei,nsanvdarying most simple repairs, it is best to involve a preservation architect or building conservator to assess the condition of phosphorus. the iron and prepare contract documents for its treatment. While molten, cast iron is easily poured into molds, As with any preservation project, the work must be making it possible to create nearly unlimited preceded by a review of local building codes and decorative and structural forms. Unlike wrought iron environmental protection regulations to determine whether abnydhastmemele,rciansgt,irroonlliisngt,ooorhaprredssainndg.briHtotlweetvoebre,sbheacpaeusde any conflicts exist with the proposed treatments. If thereare conflicts, particularly with cleaning techniques or painting it is more rigid and more resistant to buckling than materials, then waivers or variances need to be negotiated, other forms ofiron, it can withstand great compression oralternative treatments or materials adopted. loads. Cast iron is relatively weak in tension, however, and fails under tensile loading with little prior Deterioration warning. Common problems encountered today with cast-iron The characteristics ofvarious types ofcast iron are construction include badly rusted or missing elements, determined by their composition and the techniques used in melting, casting, and heat treatment. impact damage, structural failures, broken joints, damage to connections, and loss ofanchorage in masonry (Figs. 7, 8). Metallurgical constituents ofcast iron that affect its brittleness, toughness, and strength include ferrite, Oxidation, or rusting, occurs rapidlv when cast iron is cementite, pearlite, and graphite carbon. Cast iron exposed to moisture and air. The minimum relative with flakes ofcarbon is called gray cast iron. The humidity necessary to promote rusting is 659?, but this "gray fracture" associated with cast iron was probably named for the gray, grainy appearanceofitsbroken edgecaused by the presence offlakes offree graphite, which account for the brittleness ofcast iron. This td£ '<^ brittleness is the important distinguishing PRACTICAL " characteristic between cast iron and mild steel. Compared with cast iron, wrought iron is relatively isazdm yyjinr sir. soft, malleable, tough, fatigue-resistant, and readily worked by forging, bending, and drawing. It is almost pure iron, with less than 1% (usually 0.02 to 0.03%) carbon. Slag variesbetween 1% and 4% ofits content and exists in a purely physical association, that is, it is not alloyed. This gives wrought iron its characteristic laminated (layered) or fibrous structure. Wrought iron can be distinguished from cast iron in several ways. Wrought-iron elements generally are simpler in form and less uniform in appearance than cast-iron elements, and contain evidence of rolling or hand working. Cast iron often contains mold lines, flashing, casting flaws, and air holes. Cast-iron elements are very uniform in appearanceand are frequently used repetitively. Cast-iron elements are often bolted orscrewed together, whereas wrought- iron pieces areeither riveted or forge-molded (heat welded) together. Mild steel is now used to fabricate new hand-worked metal work and to repair old wrought-iron elements. Mild steel is an alloy ofiron and is not more than 2% carbon, which is strong but easily worked in block or ingot form. Mild steel is not as resistant to corrosion as i either wrought iron or cast iron. Fig. 6. Sheet from a late 19th century manufacturer's tradecatalog illustrates tomeoftheproductsavailablefrom foundries, suchas storefronts,girde)s and beams, columns, stairs, window lintelsand sills and roofcrestings. Courtesy: Albany Instituteo) HistoryandArt. on thedifference in potential between the two metals, their relative surface areas, and time. If the more noblemetal (higher position in electrochemical series) is much larger in Fig. 7. Despitemi area than the baser, or less noble, metal, thedeterioration of impamcatmthat shattered the baser metal will be more rapid and severe. Ifthemore the castings, noble metal is much smaller in area than the baser metal, this fencepost the deterioration of the baser metal will be much less remains upright, demonstrating the significant. Cast iron will be attacked and corroded when it great strength ofcast is adjacent to more noble metals such as lead or copper. iron. Originally, the post was field together bya long bolt that extended Fig. 9. Galvanic corrosion occurred from the finial to the whereapatchof base. Photo: joint G. copperwas installed Waite. alongside thecast- iron capat thebase ofa fountain. The useofteme-coated stainless flashings withappropriate caulking wouldhavi been a moresuitabh figure can be lower in the presence ofcorrosiveagents, such repair. Photo: joint as sea water, salt air, acids, acid precipitation, soils, and G. Waite. somesulfurcompounds present in the atmosphere, which act as catalysts in the oxidation process. Rusting is accelerated in situations where architectural details provide pockets or crevices to trap and hold liquid corrosiveagents. Furthermore, once a rust film forms, its porous surface acts as a reservoir for liquids, which in turn causes further corrosion. If this process is not arrested, it will continue Graphitization ofcast iron, a less common problem, occurs until the iron is entirely consumed by corrosion, leaving in the presence ofacid precipitation or seawater. As the nothing but rust. iron corrodes, the porous graphite (soft carbon) corrosion wGahlevnantiwcocdoirsrsoismiiolnarismeatnaellsercetarcotchteomgiectahleracitnitohnetphratesreensculetsof rAessiadrueesuilst,imtphreecgansat-tierdonwietlhemiennstolruebtlaeincsoritrsoaspiopneaprraondcucetas.nd an electrolyte, such as water containing salts or hydrogen shape but is weaker structurally. Graphitization occurs ions (Fig. 9). The severity ofthe galvanic corrosion is based where cast iron is left unpainted for long periods or where caulked joints have failed and acidic rainwater has corrodec pieces from the backside. Testing and identification of graphitization is accomplished by scraping through the surface with a knife to reveal the crumbling of the iron beneath. Where extensive graphitization occurs, usually th only solution is replacement of the damaged element. Castings mayalsobe fractured or flawed as a result of imperfections in the original manufacturing process, such a air holes, cracks, and cinders, orcold shuts (caused by the "freezing" ofthe surface of the molten iron during casting because ofimproper or interrupted pouring). Brittleness is another problem occasionally found in old cast-iron elements. It may be a resultofexcessive phosphorus in the iron, or ofchilling during the casting process. Condition Assessment Before establishing the appropriate treatment for cast-iron elements in a building or structure, an evaluation should be made of the property's historical and architectural significanceand alterations, along with its present condition. Ifthe work involves more than routine maintenance, a qualified professional should be engaged to Fig. 8. Structuralcracks,gapsat joints between components,anda develop a historic structure report which sets forth the largeopening wherepartoftheconsolebracket is missingare the historical development ofthe property, documents its problemsevident in this cast-ironassembly. Photo: Ford, Powell & existingcondition, identifies problems ofrepair, and Carson. provides a detailed listing ofrecommended work items with priorities. Through this process the significance and condition of the cast iron can be evaluated and appropriate treatments proposed. For fences, or for single components ofa building sin n as a facade, a similarbut less extensive analytical procedure should be followed. Thenature and extent of the problems with the cast-iron elements mustbe well understood before proceeding with work. If the problems are minor, such as surfacecorrosion, flaking paint, and failed caulking, the property ownermay beable to undertake the repairs by working directly with a knowledgeable contractor. If there are majorproblems or extensivedamage to thecast iron, it isbest to secure the services ofan architect or conservator who specializes in the conservation ofhistoric buildings. Depending on the scope ofwork, contract documents can range from outline specifications to complete working drawings with annotated photographs and specifications To thoroughly assess the condition of the ironwork, a close physical inspection mustbe undertaken ofevery section of the iron construction including bolts, fasteners, and brackets (Fig. 10). Typically, scaffolding ora mechanical lift is 4 h elamrpgleosyterudctfuorresc.losReeimnosvpaecltioofnseolfecatcaarseta-siroofnpfaaicnatdemaoryObteher GFiagl.ve1s1t.onM,ajTeoxracsrarcekssulitnedthferopmiertsheoftrtahnissfcearsotf-ilrooandsotnotroeftrhoentirionn from the only means to determine the exactcondition of internal brickpiers eroded by risingdamp. This crack was connections, metal fasteners, and intersections or crevices inappropriatelyfilled with concrete, which trapped moistureand that might trap water. accelerated internalcorrosion,pushing the iron furtherapart. Photo: & Ford, Powell Carson. FAILEDPATCH DETERIORATED FLASHING. RAISED EDGES MISSINGPIECEOF SOFFIT MOLDING HOLE' FRACTUREINCASTING OPEN JOINTS FRACTURE IN CASTING OPENJOINTAT SCROLL — MISSING LEAVES MISSING LEAVES ANDSCROLLFROM CAPITAL DETERIORATED FLASHING,GAP ATEDGE HOLE ANDOPEN JOINT CORROSION STRIPFLASHING LACKS CAULK '0. Piningclose-up inspection oftheGunther Building in New YorkCity,photographs ofeach bay were taken to use in a surveyoj existing conditions. Photo: Willco\ T>unn.