by Jennifer Gleisberg
Across the country, communities are preserving and restoring historically significant architectural façades recognized for ornamental sheet metal and cast-iron features such as colonnades, domed roofs, cornice sections, dentil blocks, frieze panels, and pendants. Many historical façades dating back to the second half of the 19th century have been neglected and damaged from impacts, moisture intrusion, corrosion, or flawed castings.1
Water intrusion resulting from the absence or failure of adequate waterproofing systems often leads to deterioration of not only the structural steel, but also the clips, brackets, and fasteners used to attach ornamental components. Fissures, or pitting in cast iron or other decorative metal pieces, can also trap moisture and airborne corrosive materials, causing oxidation or rust to occur over time.
Restoring these landmarks to like-new condition requires craftsmanship, technical expertise, and high-performance coating systems that comply with demanding standards for aesthetics, durability, and resistance to corrosion and ultraviolet (UV) light.2 This marriage of skill and technology is especially evident in the three projects highlighted in this article:
- San Francisco’s Hallidie Building;
- Zions Cooperative Mercantile Institution (ZCMI) cast-iron storefront in Salt Lake City, Utah; and
- the cast-iron domed roof façade of the Miami County Courthouse in Troy, Ohio.
The Hallidie Building’s curtain wall
After 2.5 years of remediation work, the iconic Hallidie Building’s main façade was complete. Architects involved with the project were McGinnis Chen Associates and preservation architects, Page & Turnbull. Additional specialists involved with the restoration included a materials scientist, sculptor, testing agency, structural engineers, curtain wall consultant, and coatings consultant.3
Named for Andrew S. Hallidie, the inventor of the cable car and a regent at the University of California, the building was listed in 1971 on the National Registry of Historic Places and the San Francisco Historic Landmarks and Districts. Originally designed by Willis Polk and constructed in 1917–1918 by the University of California, the building is noted for its glass curtain wall façade, which was considered unique for its time, but has now become a common element in modern architecture.4
The building is described in San Francisco: Building the Dream City, in the following passage:
The glass façade was hung, curtain like, away from the actual structural frame of the building, in a separate frame of elaborate cast iron, with ornate fire escapes at either side. The ornamental iron fretwork relieves the cold severity of an all-glass wall, and the result is highly decorative.5
Annie K. Lo, LEED AP, project manager for McGinnis Chen Associates, was responsible for evaluating, labeling, photographing, and documenting each piece of the building’s curtain wall, frieze panels, ornamental balconies, and fire escapes. She explained the uniqueness of the glazed curtain wall at the time of construction is significant. Considering available technology in 1918, Polk was inventing something, rather than using an example to model after.6
Numerous challenges were encountered with the Hallidie Building’s water-damaged structural steel, corroded frieze panels of stamped zinc, and ornamental fire escapes and balconies. At the time of construction, sealants or flashing with adequate waterproofing were not available. Also, the design did not support metal expansion and contraction normally required in a curtain wall.
Phase I of the restoration involved removal, repair, and reinstallation of approximately 735 sheet metal and railing components for the ornamental balconies and fire escapes, along with 360 windows around the perimeter of the curtain wall façade. Phase II of the project, completed April, involved the removal, repair, and reinstallation of the remaining 153 windows in the curtain wall.
For the project team, getting to Phase I was a challenge, explained Lo.
“We started working with the city and the Historic Preservation Commission on obtaining approvals to remove the metal pieces since this was a salvage and disassembly project for a notable landmark building,” she said. “Each piece had to be tagged and given an identification number so it could be tracked throughout the repair process and reinstalled on the building.”
Originally, the project’s architects envisioned restoring the frieze panels by making spot repairs to severely corroded sections. This repair methodology was changed after the existing lead coatings were removed and the severity of damage to the panels was determined. The back side of the panels was reinforced with a spray-applied layer of fiberglass, which enabled more of the original historic material to be salvaged.
Another change involved the method used by the coating applicator to remove the multiple layers of lead paint that had built up over decades. Early in the project, it was envisioned the paint would be removed by dipping pieces into a chemical stripping solution. However, this method proved too slow and did not provide the cleaning needed to apply a zinc-rich, aromatic urethane primer.
Due to the fragile and thin condition of ornamental cornice sections, dentil blocks, frieze panels, and pendants, these components were prepared in accordance with Society for Protective Coatings/NACE International–The Corrosion Society (SSPC-SP6/NACE) No. 3, Commercial Blast Cleaning, prior to the application of the primer. Window frames, window sashes, metal grates, and railing sections were prepared in accordance with SSPC-SP10/NACE No. 2, Near White Blast Cleaning, before priming with the same zinc-rich coating.
Structural steel used to support the ornamental balconies was so badly corroded from water infiltration it could not be salvaged or reused and had to be completely replaced.
Removal of ornamental metal was carefully monitored for compliance with environmental regulations, in accordance with Section 02085, Federal and State Occupational Health and Safety Administration (FED-OSHA) 29 Code of Federal Regulations (CFR) 1019, 1025, and California-OSHA under Title 8, CCR 1532.1, which relates to the proper capture and disposal of lead-based paint.
All surface preparation and paint removal was performed in blasting chambers offsite. The exterior coating system for both ornamental metal and structural steel consisted of a spray-applied zinc-rich primer, an aliphatic urethane intermediate coat, and a fluoropolymer topcoat in both satin and semi-gloss finishes.
The coating system was selected to achieve the highest level of performance in terms of color retention and longevity. Keeping the associated costs in mind, the durability and lifespan of the coating system was an important concern. A zinc-rich primer offering a high level of corrosion protection on bare metal was specified for the project. When this is applied with a proper intermediate coat, additional corrosion protection is attained.
Fluoropolymer topcoats offer aesthetic performance, gloss retention, and protection against UV light and climate conditions. The coatings were custom-matched to the building’s original colors. The project’s preservation architectural firm conducted a coating analysis that involved scraping down to the original first and second coatings and matching them to a Munsell color card, which was then provided to the coatings manufacturer.
Blue and gold were the original colors used on the building and the coatings created through the color match were accurate. Originally, a gold coating resembling true gold leaf was used on ornamental sheet metal and designers were able to replicate this. Once the ornamental metal pieces were reinstalled onto the curtain wall, coatings were used to touch-up welds and scratches.
Early this year, the Hallidie Building project was named winner of the Charles G. Munger Award at the annual Structure Awards sponsored by the SSPC. The award is presented to an outstanding industrial or commercial coatings project demonstrating longevity.7
Restoring the ZCMI façade
Recognized as one of the earliest department stores in the nation, Zions Cooperative Mercantile Institution was founded by Brigham Young in 1868. The structure’s three-story, classical cast-iron façade was constructed in three separate phases, beginning with its center section in 1876, followed by an extension to the south in 1880, and a north addition in 1901. The façade was placed on the National Register of Historic Places in 1970 and was subsequently listed on Salt Lake City’s historic register.8
Cast-iron façades were popularized throughout the second half of the 19th century due to their fire-resistant properties and ability to replicate sandstone and limestone. In addition to providing structural support to upper floors, cast iron also allowed large display windows for merchandise, allowing light into the building’s interior.9
In 1971, plans for a new downtown mall had called for demolition of the original building, including its cast-iron façade. A coalition of the Utah Heritage Foundation and community preservationists was successful in saving and restoring the façade to become part of the ZCMI Center Mall. Restoration architect Steven T. Baird was enlisted to develop procedures for dismantling, reconditioning, and reconstructing the façade from 1974 to 1976. Working primarily out of his garage, Baird is credited with creating the model for other cast iron renovation efforts across the country.10More than three decades later, the company owned and operated by Baird’s sons—Historical Arts and Casting Inc.—was commissioned to restore the façade a second time as part of the mixed-use redevelopment project. Today, the landmark façade fronts the west face of Salt Lake City’s new Macy’s department store.11
Measuring 23 x 42 m (75 x 140 ft), the façade consists of cast-iron colonnades with 63 bays for windows and openings, a cornice section made of galvanized sheet metal, and thousands of mechanically fastened ornate castings. For both restoration projects, each component was carefully numbered, cataloged, and moved offsite for reconditioning or replacement.
Restoring historical cast-iron façades like ZCMI presents major challenges. Cast iron’s ability to replicate stone was enhanced by mixing sand into paint, which was then applied in thick coats to the casting. Locating fasteners under several layers of old paint was a challenge during the first restoration in the 1970s. Additionally, many of the façade’s original cast-iron components were severely deteriorated due to moisture penetration and had to be recast.12
The preferred method for removing old paint from cast iron is blast-cleaning in accordance with SSPC-SP6/NACE No. 3, followed immediately by the application of a primer to prevent surface rust. Since most old paint found on historic cast-iron façades contains lead, blasting debris must be captured and disposed of in accordance with U.S. Environmental Protection Agency (EPA) regulations (e.g. 40 CFR Subchapter 1, “Solid Wastes.”13
When surface preparation uncovered pitting or other imperfections in the cast iron, a surfacing epoxy to recondition the surface, followed by zinc-rich aromatic urethane, and intermediate epoxy primers that doubled as a field-applied tie coat, were used. Structural steel used to secure cast-iron components to the building was blast-cleaned and primed by the fabricator with a zinc-rich aromatic urethane primer.
The façade’s galvanized-metal sections were prepared in accordance with SSPC-SP1, Solvent Cleaning. Abrasive blasting was originally tried, but the sheet metal was too thin; therefore a chemical stripper on the metal was used and it was then pressure-washed.
The cornice sections were shop-primed with a polyamide epoxy coating, followed by a finish coat of high-solids fluoropolymer coating specified for its ultraviolet (UV) light stability and durability. Four custom colors were specified, including a metallic gold that mimicked 24-karat gold leafing. An acrylic polyurethane metallic clearcoat was applied over the metallic gold finish wherever it was used.
During reassembly and the application of field coatings the façade was surrounded by scaffolding and enclosed to help control environmental conditions. Tie-coats, fluoropolymer finish coats, and gold accent finishes were brush-, roller-, and spray-applied to the cast-iron colonnades and ornate castings then reattached to the façade by screws using detailed drawings as a guide.
Approximately 2300 work hours and 1892 L (500 gal) of coatings were needed to complete the field coatings and installation, which was completed in the spring of 2012.14
Bringing order to the Miami County Courthouse
The decorative exterior of the Miami County Courthouse in Ohio, constructed between 1885 and 1888, was also restored. The original Greco-Roman design by Joseph Warren Yost featured four corner domes, a central dome, and four pavilions built of cast-iron cladding over riveted iron frameworks.15
After nearly a century, the building’s decorative cast iron had severely corroded due to water intrusion, which threatened the building’s interior courtrooms that had been renovated in 1982. In 1989, an architectural firm was contracted to conduct a condition survey that included a preliminary specification for what would eventually become the largest restoration of cast-iron construction in the country.16
In 1995, the county retained a construction management team to oversee the project. The following year, a local construction company was awarded the primary restoration contract, which called for dismantling and restoring the cast iron from the building’s five domes and four pavilions. The contract also called for replacement of the building’s slate roof, copper flashing, windows, exterior lighting, copper statues, and clock tower.
Before cast-iron components could be removed, more than 18,143 kg (40,000 lb) of pigeon waste and other debris was taken from the belfry. The disposal of this material followed the same guidelines as removal of asbestos or lead. 17, 18
Rather than prepare the cast iron for recoating onsite, it was prepared, primed, and given an intermediate coat offsite. Once the material was returned and reinstalled, the field touch-up and finish coats were applied.
Coating consultant Dan Haines compared the removal of cast-iron components to “an architectural dig”—each piece of the cladding was cataloged using a numerical coding system identifying the exact location it needed to be reinstalled.
Crews worked from scaffolding and used an exterior elevator lift to move more than 15,000 cast-iron pieces, which were dismantled and taken offsite in phases to be reconditioned or replaced. Historical Arts and Casting was responsible for recasting more than 50 percent of the severely corroded cast iron, requiring more than 700 patterns to be manufactured.19
It was determined a lack of sufficient waterproofing led to the failure of the decorative cast iron on the courthouse, so replacement pieces were molded with flanges and lap joints enabling moisture to run off rather than collect on the surface. Vertical and horizontal joints were caulked with a silicone system to prevent water penetration and adhesion testing was conducted to verify the coating system’s ability to bond to the prepared cast-iron components.20
Both replacement parts and reusable cast-iron components ranging in weight were prepared in accordance with SSPC-SP6/NACE No. 3, Commercial Blast Cleaning, and shop-primed with a zinc-rich aromatic urethane primer. They also received a shop-applied intermediate coat of polyamide epoxy coating.
Structural iron was cleaned and field-coated with a high-build modified polyamidoamine epoxy coating. Once the shop-primed cast-iron cladding was reinstalled, it received a field-applied coat of a light gray aliphatic acrylic polyurethane topcoat, followed by a urethane clear coat. 21
The restoration and preservation of historically significant sheet metal and cast-iron façades requires the special skills and expertise of craftsmen and professionals who share an understanding and appreciation of these architectural treasures. These specialists spend countless hours assessing the condition of structural and ornamental metalwork, dismantling components, removing old coatings, and restoring or replacing thousands of individual pieces. Given the exhaustive amount of work and care involved with restoring these national landmarks, specifiers must rely on high-performance coating systems that offer long-term substrate aesthetics and protection against corrosion caused by moisture intrusion, UV light, and thermal cycling.
1 The resource is written by J. Waite, AIA, with an introduction by cast-iron preservationist Margot Gayle. See, Preservation Briefs, “The Maintenance and Repair of Architectural Cast Iron,” 1991, Technical Preservation Services, National Park Service at www.cr.nps.gov/hps/tps/briefs/brief27.htm. (back to top)
2 Important standards include ASTM D4060, Standard Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser; ASTM D4141, Standard Practice for Conducting Black Box and Solar Concentrating Exposures of Coatings; ASTM D4587, Standard Practice for Fluorescent UV-Condensation Exposures of Coatings; and ASTM B117, Standard Practice for Operating Salt Spray (Fog) Apparatus. (back to top)
3 For more, visit American Institute of Architects (AIA), San Francisco Chapter’s website at www.aiasf.org/about/history/hallidie-renovation/. (back to top)
4 For more, see Business Wire’s news release, “San Francisco’s Urban Design Community Celebrates Restored Hallidie Building” at www.businesswire.com/news/home/20130501006221/en/San-Francisco%E2%80%99s-Urban-Design-Community-Celebrates-Restored. (back to top)
5 See J.B. Alexander’s, San Francisco: Building the Dream City (Scottwall Associates, 2002). (back to top)
6 This comes from an interview with Lo in April 2013. (back to top)
7 Visit, Durability + Design’s article, “Curtain Wall Project Earns Accolades,” at www.durabilityanddesign.com/news/?fuseaction=view&id=9002. (back to top)
8 Visit www.downtownrising.com/DTR-media/city-creek/downloads/ZCMI_Facade_Fact_Sheet.pdf. (back to top)
9 See Note 1. (back to top)
10 See Salt Lake Magazine’s article, “Restoration 2.0,” by J. Pugh. Visit www.saltlakemagazine.com/blog/2012/01/12/restoration-20/. Historical Arts and Casting also has a video, ZCMI A Legacy Cast in Iron. (back to top)
11 For more, see City Creek Reserve’s news release, A Familiar Face Returns to Main Street: ZCMI Façade is Back at www.downtownrising.com/DTR-media/city-creek/downloads/ZCMI_Facade_Release.pdf. (back to top)
12 This is from an interview with R. Baird in April 2013. An interview was also conducted with M. Call in February 2012. (back to top)
13 For more, see R. Baird and Historical Arts and Casting’s “Restoring Cast Iron Facades (Part 1),” at www.historicalarts.net/restoring-cast-iron-facades-part-1-of-2/. (back to top)
14 This is also from an interview conducted by the author with M. Call in February 2012. (back to top)
15 For more see R. Baird and Historical Arts and Casting’s “The Rebirth of A Cast Iron Gem (Part 1).” (back to top)
16 See Note 15. (back to top)
17 For more see R. Baird and Historical Arts and Casting’s “The Rebirth of A Cast Iron Gem (Part 2). (back to top)
18 This is from an interview conducted with D. Haines in April 2013. (back to top)
19 See Note 17. (back to top)
20 See Note 17. (back to top)
21 See Note 18. (back to top)
Jennifer Gleisberg is an architectural sales coordinator for Tnemec Company Inc., where she provides support for sales and marketing of protective coatings for concrete, steel, concrete masonry unit (CMU), dry wall, and decorative cast iron and sheet metal substrates used on historical landmarks. She is an active member, or has received credentials, from NACE (NACE Coatings Inspector – Level I Certified), The Society of Protective Coatings (SSPC), and the United States Green Building Council (USGBC), where she is a Leadership in Energy and Environmental Design (LEED) Green Associate (GA). With more than 10 years of experience in the coatings industry, Gleisberg brings a customer service perspective to architectural projects that require coating solutions for lasting aesthetics, as well as protection from corrosion, impact and abrasion. She can be contacted at email@example.com.
To read the sidebars about the project teams, click here.