Gilded Age Revival: The Frick Collection

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Located on Fifth Avenue on the Upper East Side of Manhattan, The Frick Collection houses the art collection of industrialist Henry Clay Frick and his wife Adelaide Clay Frick in their 1914 Gilded Age mansion. Through several building renovations spanning between 1935 and 2011, the museum expanded its footprint by enlarging existing buildings and constructing new ones. Because of the renovations and the long timeline over which they occurred, The Frick Collection contains an expansive array of archaic structural systems hidden behind its opulent architectural finishes.

The original Beaux-Arts mansion was designed by Carrère and Hastings in 1914 with the intention of opening the residence to the public and sharing the Fricks’ private art collection after their deaths. In 1935, after Adelaide’s death, their daughter Helen hired architect John Russell Pope, who seamlessly doubled the footprint of the mansion to create a museum that included two large galleries with skylights, a new interior garden (the Garden Court), the Music Room, and the nine-story Frick Art Research Library (FARL). During World War II, the museum also constructed a three-story below-grade art storage vault to protect its collection. A later 1977 addition added the single-story Reception Hall, along with the 70th Street Garden. The museum, including the historic exterior gardens, is a National Historic Landmark. In 2011, the Frick enclosed an extant garden portico to create an additional gallery within its footprint.

In 2017, The Frick Collection began a new phase of expansion and renovation that would allow the museum to showcase its expanded collection, modernize back-of-house facilities, and improve energy efficiency. The project included a narrow nine-story horizontal addition and a new bulkhead at the FARL, a three-story vertical addition above the Music Room, and a one-story vertical addition above the Reception Hall. The renovation also included the removal of the art storage vault to allow the construction of a new auditorium, restoration of the second floor of the mansion for conversion to gallery space, replacement of skylights, and the addition of new stairs and elevators to improve visitor circulation. The complicated project was rife with challenges associated with the repair and strengthening of numerous archaic structural systems throughout the historic buildings.

Simpson Gumpertz & Heger (SGH) served as the Engineer of Record to design the renovation and expansion.

As a result of The Frick Collection’s history of construction, SGH encountered structural systems spanning the six decades of previous renovations. The structural floor systems within each building often comprised multiple systems, including draped-mesh cinder concrete slabs, slagblok slabs, formed stone concrete slabs, flat-arch terracotta slabs, terracotta plank slabs, and the obscure “stack-slab” system. The authors analyzed, repaired, and strengthened these floor systems for increased loading and designed unique details for new floor penetrations.

At the library stack levels of the FARL, the floors are a proprietary system of stack slabs, originally engineered by Snead and Company. These floors are supported by rows of closely-spaced double-angle steel posts and hangers hidden within the library stacks (Fig. 1). The posts and hangers are supported by steel-framed “strong floors” that support up to three levels of library stacks. The floor systems include 2½ inch x 2½ inch steel double-angles that span between the posts and hangers. These angles are embedded in and support one-way 3½ inch thick concrete floor slabs. The limited capacity of these slabs, limited head-height of the stacks, and the interconnected nature of the system between multiple floors curtailed the options for structural modifications.

At limited locations, the MEP engineer required new mechanical penetrations through the stack slabs. To frame these openings, SGH decided to re-support the slabs by welding 1-inch thick shims to the underside of the horizontal legs of the slab’s support angle. The contractor installed WT steel sections that spanned between the angles and connected to the shims and then shimmed the WTs tight to the underside of the slab only at the perimeter of the opening.

Draped-mesh cinder concrete floor slabs, also known as short-span construction or cinder-arch slabs, were common for floor construction between the 1920s and the 1950s. The design team encountered this system throughout the Music Room and the FARL. This system comprises wire mesh draped over the top flanges of upset steel floor framing that is encased in a 4-inch thick low-strength cinder-concrete slab topped with a 4-inch lightweight non-structural layer of cinder fill and a 1-inch cement layer. The structural capacity of this system results from the catenary action tension force in the wire mesh. Empirical formulas for the capacity of these slabs are included in the 1968 New York City Building Code, in which the key variable is a “continuity” factor that accounts for mesh continuity (e.g., at an interior bay) or anchorage (e.g., at an end bay).

Project infrastructure for MEP systems required widespread floor openings. Cutting the wire mesh for the new openings caused a loss of catenary action at the opening and typically resulted in changing the mesh continuity of the adjacent bays (from interior bay to end bay). Prior to cutting the mesh, SGH specified local removal of the cover over the steel beams and welding of the wire mesh to the steel beams for anchorage. Then, the team framed the openings with flat steel channels (Fig. 2). The solution did not require removal and replacement of the slab in the bay with the new opening. Instead, additional flat channels in the design shortened the span of the remaining slab that functioned as plain concrete. At midspan of the adjacent bays, flat channels span perpendicular to the direction of the slab to offset the reduction in strength caused by the change in mesh continuity.

During the authors’ field investigation for the project, we extracted samples from steel beams at several locations and found that the steel was not weldable in specific areas, rendering the above-described detail, shown in Figure 2, unfeasible. An alternate solution included removal of the cinder fill at newly-created end bays and replacement with a reinforced lightweight concrete topping slab, placed directly over the existing cinder-concrete slab (Fig. 3). The new topping slab was designed to span from beam-to-beam, and the existing cinder concrete acted as stay-in formwork. Finally, the design team analyzed the existing beams and their connections for the increased load from the new topping slab, but typically these beams and connections did not require strengthening.

The team also encountered slagblok slabs at several locations within the FARL. This slab system is comprised of a two-way grid of reinforced concrete joists below a thin concrete slab spanning to concrete-encased steel girders. The areas between the ribs are infilled with non-structural slagblok, which serve as a stay-in formwork.

When designing support for penetrations in these slabs, the relative size of the penetration with respect to the joists was critical. SGH coordinated with the architect and mechanical engineer to minimize penetrations through multiple joists. Where small penetrations only interrupted one joist, supplemental steel angles were added with the horizontal leg re-supporting the portions of the slabs around the openings and the vertical leg through-bolted to the remaining joists. At larger penetrations that interrupted multiple joists, new steel framing below the joists framed the openings. Because the existing steel beams extended below the underside of the slab, WTs welded to the bottom flanges functioned as “web extenders” that allowed for connection of new steel framing.

Other locations required infill of existing openings created by previously cut concrete joists. Limited demolition at the existing joists exposed the ends of the cut reinforcing, and the contractor installed couplers to extend the rebar and re-established the continuity of the joists in both directions (Fig. 4).

In the mansion, the floors comprise structural clay (terracotta) tile flat-arch floor construction, while the roof is hollow clay tile plank construction. Structural hollow clay flat-arch construction consists of three types of hollow clay block shapes that interlock and span between steel framing. The “skew block” is set against the webs of steel beams on one side and a skew plane on the other side forms the arch spring. The skew blocks interlock with an “inter-block,” and a “key” is finally placed in the middle of the span to distribute loads outward toward the beams. The arching action allows the gravity loads to be transferred to the steel via interlocking and thrust loads. Steel tie rods extend through the flat-arch construction and connect between the webs of adjacent steel beams to resist unbalanced thrust loads during construction and at end spans. Non-structural cinder fill is placed atop the structural clay blocks and steel beams to distribute the loads and provide fire protection to the top of the steel beams.

Creating large openings within flat-arch floor systems interrupts the thrust-shear arching action created by the geometry of the blocks in the span. As a result, where the project required new floor openings, it was necessary to demolish the full span of the flat-arch system between beams over the width of the opening. When the clay tile is removed, the existing steel beam at the ends of the opening is subjected to the unbalanced thrust load from the adjacent bays and needs to be analyzed for weak-axis bending. To reinstate the slab around the openings that were not full-span, the team installed steel framing between the existing steel beams, framed the new opening, and placed a new concrete-on-metal-deck slab. The new steel beams serve two purposes: in addition to supporting the new portion of the slab, they also brace the existing beams to resist the unbalanced thrust loads between tie rods.

At the start of the project and under SGH direction, the contractor extracted coupon samples from representative existing steel beams in each of the buildings to perform chemical analysis and laboratory testing to determine the composition, material properties, and weldability requirements for each vintage of steel. The project site contained four different steel compositions, with varying weldability requirements.

The 1935 expansion included the Oval Gallery and the iconic Garden Court, which both featured hip-gabled skylights supported by steel trusses featuring riveted connections (Fig. 5). The museum needed to replace the existing skylight’s glazing to improve the thermal performance and provide enhanced ultra-violet protection for their priceless collection. The facade consultant specified the replacement of the original single-pane glazing with much heavier triple-pane glazing, along with new shade louvers. Additionally, The Frick Collection wanted to add a fall-arrest system at the ridge of the skylights to accommodate cleaning and future facade maintenance.

The original trusses support an access catwalk that allowed up-close access to field measure and document the trusses, purlins, and their connections. The structural system comprises five different truss configurations and, over the East Gallery, a horizontal plan offset of the skylight framing resulting in a “jog” of the ridge elements, atypical framing, and double cantilevered purlins. To support the loads imposed by the new fall-arrest system, the existing ridge steel channels were replaced with new HSS sections and the ridge connections to the trusses were reinforced (Fig. 6). The team also analyzed the trusses, purlins, and their riveted connections for the increased loads associated with the new skylights and shade louvers. At the locations where the existing trusses and connections had insufficient capacity, the team designed steel strengthening, while coordinating with the new louver, lighting, and MEP systems.

In the FARL, building setbacks and complicated geometry resulting from stack slabs and strong floors required an indirect column gravity load path, where columns are interrupted by double transfer girders at several floors. The renovation featured increased loads at the roof due to enlargement of a limestone-clad mechanical roof bulkhead for new boilers and cooling towers.
The convoluted load path and increased loads necessitated the evaluation and strengthening of many riveted connections of the double transfer girders. Typically, access to these connections was limited to one side, rendering the strengthening options more challenging. To minimize shoring, SGH developed supplemental connection details that could be installed prior to the increase of loads, while leaving the existing connections in place. For example, at riveted connections to beam webs, the team installed new stiffened beam-seat connections. SGH considered “locked-in” loads at existing riveted connections as well as load sharing with the strengthened portion of the connection and closely coordinated the construction sequence with the contractor.

At one location, the connection consisted of double-girder webs riveted directly to the flanges of the columns and the bottom flanges also supported by riveted seats. Because of historic finishes in the space below, the contractor requested a solution that could be installed from the top side of the slab. SGH designed a welded stub column to extend the existing downward column, which terminated at the top flange of the beam, above the slab level (Figure 7). New “web extender” plates were then connected to the top flange of existing girder webs, which were connected to the new stub column. This detail was concealed within a built-up slab that was part of the original design.

The 1940s Art Vault, which was built at the southeast corner of the property to safely house the collections during the Second World War and remained during the Cold War, was constructed with “Steelcrete” reinforced concrete. The original vault had one-story above-grade and three levels below-grade. After the threat of the Cold War subsided, The Frick Collection demolished the above-grade portion of the Art Vault to make space for the 70th Street Garden, but the below-grade levels remained. The vault was a heavily fortified structure comprising double concrete walls with sand layer between them and two sand-filled floor levels at grade (Figs. 8-9). The concrete structure included Steelcrete reinforcing above the top of bedrock and conventional reinforcing below. Steelcrete was a thick expanded metal sheet reinforcing product produced by Consolidated Expanded Metal Companies. Layers of Steelcrete were densely placed 2½ inches on center transverse in the walls and slabs, creating heavily reinforced concrete sections.

The current renovation required the removal of two below-grade levels of the Art Vault, as well as its west and north walls for construction of the Stephen A. Schwarzman Auditorium. Due to the removal of the existing intermediate slabs, the team analyzed the Steelcrete-reinforced east and south walls for the new 30-foot unbraced wall height (triple of the original) from the stage level to the garden slab to resist lateral earth pressures. During demolition of the vault, SGH also confirmed the as-built construction and splices between the Steelcrete and the conventional reinforced concrete sections to verify that splices had adequate strength to develop reinforcement at the joints.

Navigating the challenges of structural strengthening of a myriad of archaic systems, while maintaining the historic architectural fabric intact, requires in-depth knowledge of the systems, extensive literature review, and some ingenuity. The Frick Collection reopened to the public in April 2025. While the collection of historic structural systems is now concealed by lavish finishes, the holistic strengthening of the structure allows for improved energy efficiency and unprecedented access to the second floor of the mansion, new special exhibition gallery spaces, and the preserved first-floor galleries. ■

Part 2 of this series will discuss the design challenges that the authors faced in modifying archaic lateral systems at The Frick Collection.

About the Authors

Lauren Feinstein, PE, is a Senior Consulting Engineer in the New York office of Simpson Gumpertz & Heger, Inc. (SGH) focused on restoration and rehabilitation of historic structures and renovation of existing buildings. (Lpfeinstein@sgh.com)

David Ribbans, PE, was previously a Consulting Engineer in the New York office of SGH for the duration of this project and focused on the repair, restoration, and strengthening of existing structures. He now works for K2M Design. (david.ribbans@gmail.com)

Kevin Poulin, PE, is a principal in the New York office of SGH specializing in the restoration and adaptive reuse of existing buildings. (Kcpoulin@sgh.com)

Filippo Masetti, PE, is an Associate Principal in the New York office of SGH with extensive experience in assessing, analyzing, repairing, and strengthening existing structures. (Fmasetti@sgh.com)