Approaching Total Reliability in Tile Repairs at the ...web.mit.edu/cron/Backup/project/guastavino/www/Koga-Oyster Bar.pdfApproaching Total Reliability in Tile Repairs at the Oyster

Approaching Total Reliability in Tile Repairs at the Oyster Bar and Whispering Gallery, Grand Central Terminal

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Authors:

Dean Koga

Director of Technical Services, Building Conservation Associates, Inc. 44 East 32nd Street, New York, NY 10016 212.777.1300 / [email protected]

B.A. Chemistry, Temple University, 1971 B.Arch, Pratt Institute, 1981

Christopher Gembinski

Senior Associate Building Conservation Associates, Inc. 44 East 32nd Street, New York, NY 10016 212.777.1300 / [email protected]

B.A. University of New Hampshire, 1988 Coursework, Boston Architecture Center, 1994 – 1996 Historic Preservation Planning Studio, Istanbul Technical University, 1997 M.S. Historic Preservation, University of Pennsylvania, 1998

Laura Buchner

Senior Conservator, Building Conservation Associates, Inc. 44 East 32nd Street, New York, NY 10016 �212.777.1300 / [email protected]

B.A. Physics and English Literature, Concordia College, Moorhead, MN, 2003 M.S. Historic Preservation, Columbia University, 2005

Derek Trelstad

Associate, Robert Silman Associates, PC. 88 University Place, New York, NY 10003 212.620.7970 / [email protected]

B.S. Mechanical Engineering, University of Vermont, 1986 Diploma, Preservation Carpentry, North Bennet Street School, 1988 M.S. Historic Preservation (Materials Science), Columbia University, 1991 Certificate in Stone Preservation, University of Pennsylvania/ICCROM, Rome, 1991

Abstract:

The Oyster Bar in Grand Central Terminal stands as one of the iconic venues in New York and among the best-known structures where Guastavino vaults and domes can be seen and experienced. Following a kitchen fire in 1997, which resulted in the loss of a significant number of original finish tile, the elegant sail vaults in the dining room were restored in a project that included repairs to original material, as well as installation of a substantial number of replica tile. After a piece of mortar reportedly fell “into a diner’s bowl of soup”, the Owner retained Building Conservation Associates (BCA) and Robert Silman Associates (RSA) in 2007 to document the condition of the ceiling. Following this investigation, BCA and RSA in 2010, developed and tested a range of approaches for cleaning and restoring the tile domes and vaults.


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During the documentation phase, BCA and RSA identified more than 3000 of the approximately 36,000 tile in the Oyster Bar as loose or potentially loose. The team had learned on other Guastavino vaults that tile that “sounded” loose were not necessarily loose, but were not completely attached either. Removing and resetting all tile that sounded at least partially detached would cause significant disruption to the operation of the Oyster Bar. Accordingly, the team divided the tile into three categories: stable, loose, and ambiguous, and then collaboratively developed several approaches to securing ambiguously attached tile in situ, as well as a specification for resetting loose tile or tile that could not be treated in situ for other reasons. The viable repair options were fully tested during a mock-up phase with a critical look at their reliability. The selected approach included installation of concealed fasteners to hold tile in place if they were not being reset.

This paper focuses on the development of a protocol that the Owner and Design Team could recognize as reliable, notwithstanding the age of the tile, their location beneath an exhibit hall, and close proximity to passing trains. The technical details of the repair options — including their advantages and disadvantages — will be discussed along with the out-of-the-box testing protocols that were developed to demonstrate the efficacy of the proposed repairs.


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Jokes about “Tile” Fish are not Funny: Approaching Total

Reliability in Tile Repairs at the Oyster Bar and Whispering

Gallery at Grand Central Terminal

The Oyster Bar and the Whispering Gallery in Grand Central Terminal stands as one of the iconic venues in New York City and among the best-known structures where Guastavino vaults and domes can be seen and experienced. Following a kitchen fire in 1997, which resulted in the loss of a significant number of original finish tile, the elegant sail vaults in the dining room were restored in a project that included repairs to original material, as well as installation of a substantial number of replica tile. In 2007, after a piece of mortar reportedly fell into a diner’s bowl of soup, the Owner retained Building Conservation Associates (BCA) and Robert Silman Associates (RSA) to document the condition of the ceiling. The scope was expanded to include the adjacent Whispering Gallery to allow full review of the Guastavino tile construction in the key public spaces in the terminal. Following this investigation, BCA and RSA, developed and tested a range of approaches for cleaning and restoring the tile domes and vaults.

The Oyster Bar and Whispering Gallery

The Oyster Bar at Grand Central Terminal, which was built in the early twentieth century, is a designated New York City Interior Landmark. Original drawings by the terminal’s architects, Warren and Wetmore, and Reed and Stem, refer to the space now occupied by the restaurant as the Suburban Waiting Room and indicate that it was to have Guastavino vaulted tile ceilings. The Guastavino Company designed and constructed the distinctive vaults in this area. Directly outside the Oyster Bar are similar vaults over a passageway known as the Whispering Gallery because of its unique acoustic properties. The vaulted ceilings consist of structural Guastavino tile vaults spanning to steel and masonry base building structure. The loads on the vaults include the self-weight of the structure, loads from the Vanderbilt Hall Floor above, and secondary loads and stresses caused by the vibration from trains using a track loop directly below the restaurant. The span of the vaults varies based on location within the restaurant, ranging from approximately 15'-0" to 31'-0". The height from the Oyster Bar floor to the underside of the vaults is approximately 15'-0". Review of the original Express Concourse framing plans and the Guastavino Suburban Waiting Room section drawings, as well as limited structural probes into the space between the Oyster Bar ceiling and the Vanderbilt Hall floor structure above, confirmed two structural systems in the existing ceiling construction: (1) a Guastavino tile vault supported by steel and masonry and (2) steel-and-concrete floor framing. The Guastavino tile vaults and arches consist of two different types of tile: concealed structural tile and architectural tile with decorative raised mortar joints. Original design drawings for the Suburban Waiting Room note that the larger vaults were to be constructed as three courses at the crown and four courses at the spring points.1 The structural tile is typically fabricated with a red clay. A print advertisement for the Guastavino Company indicates that the finish tile in the Oyster Bar were initially a “buff-colored tile in a matte glaze.”2 The glazed tile in the center

1 R. Guastavino Co., Suburban Waiting Room – NYC & HRRR Co. Grand Central Terminal Station Building (June 21,

1911/October 11, 1911), Drawing No. 3. 2 “Guastavino Print Advertising,” Guastavino Co. (1885-1962) Catalogue of Works in Catalonia and America, edited by

Salvador Tarrago (Barcelona: COAC, 2002), 77.


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fields of the vaults and arches have a ribbed surface and are laid in a herringbone pattern (Figure 1). The borders of the vaults and arches are comprised of smooth tile of a variety of shapes. 1997 Fire and Restoration

On June 29, 1997, a fire broke out in the kitchen area along the south end of the Oyster Bar. The fire burned decorative wood elements on the walls, doorways, and the floor; furnishings and fixtures melted; floor tile popped up, buckled, and shifted; and the restaurant sustained extensive smoke damage. Reportedly, “the underside of the vaults, or finished tile, encountered temperatures in excess of 400°F.”3 The decorative tile and terra-cotta vaults were found to have behaved in accordance with the fire and water tests conducted by the Guastavino Company in 1897 on a vault similar to those in the Oyster Bar.4 The glaze on the tile closest to the fire appeared to change to a gray-blue color from the extreme heat, and hundreds of ceramic tile fell or became loose.5 A cleaning and restoration campaign of the tile ceiling began immediately after the fire with the intent to reopen the restaurant in just a few weeks. Approximately 11,000 damaged architectural tile were reportedly replaced, and the remaining original tile and mortar were cleaned. Some damaged tile in the kitchen were removed and not replaced.6 Existing Conditions and Safety BCA and RSA reviewed reports and journal articles prepared in the aftermath of the 1997 fire, reviewed available original drawings, examined all visible portions of the Guastavino ceiling, conducted probes into the interstitial spaces between the Guastavino vaults and the Vanderbilt Hall floor above, and analyzed the original and replacement mortar materials. During the ”sounding” survey, BCA developed a technique to differentiate between loose and “ambiguous” (hollow sounding) tiles. Tile found to be hollow sounding or detached was often an indication that the architectural layer had lost its bond to the mortar and/or the structural tile substrate. In these cases, the support of the individual tile of the architectural layer is dependent on the “cohesive” nature of the vault and the raised pointing mortar holding the tile in place. 7 Unfortunately, the original raised mortar joints are often disintegrating, detached, or otherwise unstable. In addition, in isolated locations the replacement raised mortar, which differs in color

3 Timothy D. Lynch (Senior Engineer, Robert Silman Associates, P.C.) to Nancy McCoy (Ehrenkrantz, Eckstut and

Kuhn, Architects), 7 August 1997, Project Files, Robert Silman Associates, P.C. 4 Robert Silman, “Structural Repairs to Fire-Damaged Guastavino Tile Vaults at Grand Central Terminal’s Oyster

Bar,” APT Bulletin 30, no. 4, Preserving Historic Guastavino Tile Ceilings, Domes, and Vaults (1999): 49. 5 Frederic R. Harris, Inc., “Oyster Bar Restaurant Draft Inspection Report,” (Metro-North Railroad Contract

#7960, August 1, 1997): 3-3. 6 Denis G. Kuhn, Russell H. Newbold, and Kate Lemos, “Restoration of the Oyster Bar at New York’s Grand

Central Terminal: A Case Study,” APT Bulletin 30, no. 4, Preserving Historic Guastavino Tile Ceilings, Domes, and Vaults (1999): 43.

7 “Cohesive” is a term that was used by Rafael Guastavino (the elder), but the vaults are not “cohesive” in the manner that he originally used the term. The documentation and mock-up process has demonstrated that there isn’t always adhesion between the architectural tile and the structural tile. The number of individual tiles that could be removed before the single-thickness of the architectural tile become unstable was not determined, so the point at which the single-thickness of architectural tile became unstable (or lost its “cohesiveness”) was not identified.


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and profile from the original, was placed only on the surface of the tile, and the joints between the replacement tile are not fully filled with mortar, resulting in some loose mortar and tile. Within the Oyster Bar and Whispering Gallery, approximately 2700 tiles were identified as loose and 3000 as ambiguous; the majority of these were original Guastavino tile. The former condition is considered potentially hazardous; the latter does not pose an immediate danger, but could become hazardous if subjected to on-going vibration. BCA also identified approximately 470 tiles that were cracked; of these fewer than 100 were considered loose and only about 90 sounded hollow. As part of the conditions assessment of the Oyster Bar ceiling, BCA and RSA designed a program of investigative probes, which included observation of the interstitial space above the Oyster Bar ceiling; isolated removal of glazed tile at the Oyster Bar ceiling; and the examination of the accessible spaces adjacent to the Oyster Bar. RSA determined that the main vaults in the Oyster Bar ceiling support the floor of Vanderbilt Hall which is located directly above the Oyster Bar through review of original framing plans, drawings of the vaults prepared by the Rafael Guastavino Company, and probes. RSA completed a finite element analysis (FEA) of one of the large vaults in the Oyster Bar to confirm that the vaults had sufficient capacity to support the floor of Vanderbilt Hall.8 Despite the deteriorated conditions of the architectural tile and mortar, RSA determined that the Guastavino vaults appeared to be in sound structural condition. When it became clear, during the restoration of the Whispering Gallery vaults, that the thickness of the vault shown on the Rafael Guastavino Company drawings which was used to develop the FEA model included the architectural tile, the results of this analysis became critical to evaluating the reliability of repairs. Based on the results of the survey, and the construction and conditions observed in the probes, as well as supporting laboratory testing of materials and structural analysis, BCA and RSA concluded that some original and new tile and mortar that are not solidly bedded to the substrate had the potential to fall and should, therefore, be considered unsound. Stabilization of such conditions was recommended as a precaution.

Design Mock- Up and Request for “100% Reliability”

In 2010, BCA and RSA designed a program of materials testing and mock-ups to facilitate development of repairs that maintained the appearance of the vaults and met the reliability criteria desired by the Owner. Originally requesting “100% reliability,” they were shown that there were too many factors affecting the tile vaults, such as the vibrations from the loop track below and an exhibit hall above, original non-mechanical attachment of tiles in place for a century, and variability of workmanship, to make such a request realistic. They tempered their position to one of stressing that the repair procedures should reliably secure and stabilize the tiles, recognizing possible adverse effects from other forces and factors. Reliability of repairs is implicit in any repair program; in this project it was made explicit. Given the constraints of budget, inherent variability in construction operations, and the need to minimize the impact on

8 The analysis assumed the existing Guastavino tile vault behaves in a linearly elastic manner. In general, this

assumption is valid if there are no cracks in the existing vault, an assumption consistent with the condition of the vaults as documented in the sounding survey. In addition, the analysis assumed that most of the horizontal thrust from the dome is transferred to ribs and resisted by a series of adjacent domes.


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the operation of both the Oyster Bar and adjacent Whispering Gallery, the design team collaborated on developing a range of repairs that would permit field testing of performance and constructability. The team had learned on other Guastavino vaults that tile that “sounded” loose were not necessarily so, but also were not completely attached. Removing and resetting all of the tiles that sounded at least partially detached would cause significant disruption to the operation of the Oyster Bar. Accordingly, BCA divided the tile into three categories: stable, loose, and ambiguous. There is no way to discern the cause of a hollow-sounding tile without removing it; some tile may be nominally adhered to the structural tile or span a void in the bedding mortar (see the section “Pointing,” below, for more detail on the mortar). Clearly, ambiguity stands in the way of reliability. The team accordingly developed several approaches to securing ambiguously attached tile in situ, as well as a specification for resetting loose tile or tile that could not be treated in situ for other reasons. The viable repair options were fully tested during the mock-up phase with a critical look at their reliability. From January 9, 2011 to March 1, 2011, Graciano Corporation executed the restoration mock-up in the northeast corner of the Oyster Bar restaurant. The mock-up was intended to inform the client of the visual and financial implications associated with different levels of restoration and to allow the design team to assess the reliability of the proposed repair options. The primary intent of the work was to establish whether “clipping” the hollow-sounding tile is an effective alternative to removal and resetting. The Graciano Corporation also restored the five vaults of the Whispering Gallery located outside the Oyster Bar Restaurant between July and October 2012. Work at the Whispering Gallery revealed more information about the vault construction and offered opportunity for the refinement of the repair approach. One vault and arch were selected for the 2010 mock-up location; the vault was divided into four quadrants, with varying restoration approaches scheduled in each quadrant. During the 2007 sounding survey, the mockup area was found to contain loose and ambiguous tile as well as deteriorated pointing mortar. The scope of work included in the mock-up therefore included:

• Removing and Resetting Loose and Hollow-Sounding Tile • Securing Hollow-Sounding Tile with Clips • Investigating and Repairing Steel Reinforcement Embedded in Tile Bedding Mortar • Raking and Repointing Joints to Match the Historic Joint Profile9

Tile Removal

The Contractor removed all loose tiles in the mock-up area by raking the mortar around the perimeter of the tiles and gently tapping the tile with a rawhide faced hammer. Most of the tiles were easily removed using this method, but some of the hollow-sounding tile remained firmly attached to the substrate. Documentation from the post-fire restoration indicated that removing isolated loose tiles was extremely difficult. Tiles that are detached from their substrate are often being held in place by compression; they are effectively squeezed between adjacent architectural tiles. When isolated tiles were removed during the previous restoration, the adjacent tiles reportedly delaminated,

9 Cleaning methods were also evaluated for removing general soiling and stains from tile.


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causing progressive failure and resulting in demolition of the entire architectural layer of tile within vaults.10 During the mock-ups it was confirmed that removal of detached tiles could result in the loss of adjacent tiles; however, the selective removal did not result in wholesale loss of the architectural tiles. Approximately 80 tiles were removed and reset as part of the mock-up; 19 of these tiles were not identified as loose or hollow sounding during the initial sounding survey. The findings from the mockup informed the estimating of the quantity of tile to be removed during the full restoration of the Whispering Gallery and Oyster Bar, as well as the time and cost to complete the repairs. By comparing the quantity of tile identified as loose or detached in the sounding survey to the actual amount of tile removed in the mockup, an approximate 20 percent increase was allotted for repairs to architectural tiles destabilized by removal of adjacent tiles. The actual amount of tiles removed in the Whispering Gallery project corresponded closely to the estimated quantity. Bedding Mortar Preparation

BCA evaluated multiple methods for preparing the existing bedding mortar before reinstalling tile. The minimal preparation consisted of brushing the existing bedding mortar free of dust and debris. Another tested method consisted of scoring the bedding mortar with a rotary grinder: parallel kerfs were cut approximately 1inch apart and 1/8–1/4-inch deep. The third method tested involved scoring the setting bed in both north-south and east-west directions. After cutting the kerfs, the contractor removed the prisms formed by the kerfs. Removing the mortar accommodated the thickness of new setting mortar so that the tile could be reset at their original elevations. BCA and RSA tested the load capacity of a variety of setting mortar mixes set on modified (chipped) and unmodified bedding mortar after the mortar cured for 72 hours. Testing included embedding 100-pound test fishing line in the setting mortar during its installation. BCA later attached a bucket to the line and progressively filled the bucket with weight to reach the 35 pound test load (Figure 2).11 Full size tiles weigh approximately three pounds. All tiles successfully sustained a load of 35 pounds, indicating that the minimal amount of surface preparation is acceptable. The tiles were not tested to failure. The tile adhesion testing program was initiated in part because the tile vaults are subject to constant vibrations from a train loop directly below the Oyster Bar. Vibrations were believed to be a factor in the detachment of the architectural tile from the structural vault. Other possible factors include poor preparation, such as dust or debris on the tile surfaces; inadequate pre-wetting of tiles prior to placement of subsequent layers of tiles; or sub-optimal curing conditions, such as low humidity or low temperatures. Conditions of the tile surface during the mock-up in the Oyster Bar and repairs at the Whispering Gallery were closely controlled to minimize effects of poor quality control that may have been present when the vaults were originally constructed. The project team anticipates that these measures will result in equal or greater reliability than the original tile construction. Despite these precautions, concern for meeting the client’s request for reliability was a driving force in developing redundant attachment for ambiguous tile conditions.

10 Timothy D. Lynch (Senior Engineer, Robert Silman Associates, P.C.) to Nancy McCoy (Ehrenkrantz, Eckstut and

Kuhn, Architects), 21 July 1997, Project Files, Robert Silman Associates, P.C. 11 Weights were added in increments: 2.5 lb., 5 lb., 7.5 lb., 15 lb., 22.5 lb., 30 lb., 35 lb.


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Clipping Tile

As an alternative to resetting tile, options for in situ stabilization repairs were evaluated. The option to face pin the partially detached tile was quickly discounted because the repairs would be highly visible in the low vaults of the Oyster Bar and Whispering Gallery. The variation of joint widths, which range from 0 inches to more than ½-inch, is one of the main challenges associated with selecting an appropriate stabilization clip for the Oyster Bar and Whispering Gallery ceilings. The raised decorative mortar is approximately ½-inch wide, which prevents it from covering clips set over wide joints. In addition, the curvature of the vaults results in offset tiles that prevent the use of rigid, flat clips or washers. Two clip configurations were ultimately selected for installation throughout the mock-up vault. The design for a composite anchor consisting of a bent sheet metal clip and a threaded stainless-steel fastener was developed by BCA and modified following review of geometric constraints and structural loading requirements. The modified anchor, developed jointly by BCA and RSA, consists of a 14-gauge stainless steel wire doubled at its midpoint and twisted to form a shaft that is embedded in the existing structural tile. The “loose ends” of the wire form legs that lap the surface of two tiles — one at each side of the anchor (Figure 3). A four-legged variant of the anchor was developed to accommodate wide joints between tiles; the two pair of legs were designed to create a combined mechanical and friction grip between the anchor and the edge of the tile (Figure 4). Fabricating such clips on site allowed them to be adapted to the varying tile configurations. The use of the multiple clip types was intended to minimize the visibility of wires at the edge of mortar joints. Both anchor types were embedded in holes drilled through joints in the architectural tile into structural tile beyond; high-strength structural adhesive was used to secure the anchor to the structural tile. There was no established protocol to test the efficacy of the twisted wire stabilization clips. BCA and RSA devised a field test to determine the pullout capacity of the anchors in the structural tile that entailed installing several anchors with a partial embedment leaving the legs proud of the tile, and incrementally attaching cast iron weights (Figure 5). Each tile weighs approximately three pounds; the anchor to structural tile connection was tested to just more than 30 pounds. The anchors were not tested to failure. RSA retained Atkinson-Noland Associates (ANA) to assist in development of a protocol and program for testing the capacity of the connection between the twisted wire anchors and Guastavino tile. ANA also completed testing, per the protocol developed with RSA, to demonstrate the capacity of the two-legged anchor lapped over the face of the architectural tiles and the four-legged anchor embedded between two tiles. Because the anchors used for pinning the Guastavino tiles were developed specifically for this project and do not have analogs in commercially-available anchors that have been tested using standard methodologies and/or equipment, the testing program was essential to develop confidence in the efficacy of the anchors. ANA’s experience with standard testing methods and equipment for testing commercially-available anchors, and their prior work on historic structures, assured that the protocol and testing procedures developed for this project were reliable and repeatable, as well as consistent with the intent of tests developed by standard-setting groups such as ASTM International. To evaluate the effectiveness of the anchors, two series of three pullout tests were performed using both two-legged and four-legged anchors, tiles, and mortar representative of those used at the Oyster Bar. The first series tested the single-wire anchors with un-cut legs. The second series tested the single and double-wire anchors with the horizontal legs cut to


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simulate the actual field installation (Figure 6). Tiles were set with the glazed face down in a bed of gypsum cement to level the tile and eliminate rocking of tile or flexure of the mortar joint during testing. The gypsum was held back from the mortar joint area so as not to bond to the anchor or pointing mortar. The effects of the raised joint on the capacity of the anchor to tile connection wasn’t considered critical; the added depth of the pointing mortar was expected to increase rather than decrease capacity. Mortar was prepared according to project specifications; after curing for seven days, three anchors of each type were tested in tension using a pulling device with a specially shaped load cell (Figure 7). Each anchor was loaded in tension until failure. Testing results indicate that the two- and four-legged anchors have an average capacity of 55 to 60 pounds. Average test results for untrimmed single-wire anchors were somewhat greater, but with wider variation, than the 55 pounds for the trimmed, single wire anchors. Given that each tile weighs approximately three pounds, these results provide a factor of safety of 30 to 60 for tile where two or four anchors, respectively, are installed to secure the tile. The mode of failure in all tests was cone-shaped tensile failure of the mortar and debonding between mortar and the glazed tile surface. For Guastavino tile with unglazed surfaces on the edge of the tile, such as typically exists at the Oyster Bar ceiling, we would expect increased mortar bond strength, and therefore, slightly higher anchor pullout values. As such, the tested values (from glazed-edge tile) are considered conservative. Steel Reinforcement Repair

Deterioration in the steel reinforcement within the structural tile was observed at the kitchen during the sounding survey, where tile were previously removed from approximately two-thirds of a vault. Removal of loose and hollow-sounding tile in the mock-up vault revealed twisted, 1/4" (approximately) square steel bar stock placed in the “bedding mortar” between the architectural tile and the first layer of red clay structural tile. In the areas where they are visible, the bars were placed at approximately 22 inches center to center in one direction; some bars were not parallel to others where they were placed to avoid openings built into the vault and to compensate for the geometry of the vault.12 At one location, preparation of the setting bed for reinstallation of tile displaced a section of the steel reinforcement (Figure 8). The downward displacement of the bar and the change in the depth of cover on the bar from the apex of the vault (where cover was shallow) to the spring of the vault (where cover was deeper) suggests that the bar may have been bent over the lower layer of tile rather than being pre-formed to the curvature of the vault. This was among the first clues that the architectural tile may have been built integrally with the structural tile, rather than applied to the underside of the completed structural vault (see the section “Pointing,” below, for more information about the construction of the vault). The displacement of this reinforcing bar (“rebar”) prevented resetting tile at an elevation that would maintain the overall curvature of the vault. Although steel reinforcement repairs were

12 Based on review of Guastavino’s US Patents 947,177 and 1,052,142, additional steel reinforcing may be present

at collar joints deeper in the vault (as measured from the face of the vault); this construction was not observed directly. The “additional” reinforcing may be placed parallel or perpendicular to the reinforcing observed. Larger bar and/or other reinforcement or embedded steel may be present at vaults with larger spans, but not observed by RSA in any of the mock-up areas and was not confirmed as being present at the larger vaults in the Whispering Gallery.


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not initially part of the mock-up scope, the displacement of the rebar required the design of a repair to address both immediate concerns about constructability of the masonry repairs and the feasibility of steel reinforcement repairs during a possible future comprehensive restoration of the vaults within the Oyster Bar. The repair involved cutting out the old bar and replacing it with a new piece of bar bent to match the curvature of the vault and welded to the existing bar. The removal of loose and previously ambiguous tile during construction in the Whispering Gallery exposed twisted steel rods embedded approximately 14 inches apart in the structural vault, much more frequently and shallower than was visible in the Oyster Bar mock-up area. This unexpected condition required the design team to re-evaluate the specified approach to resetting the tile that included the modification of the existing setting bed. The project team anticipated that removing the setting bed around the steel reinforcement to a depth of ¼-inch, which allowed the reinstallation of tile to maintain the original surface plane of the vault, would dislodge significantly more rebar than previously expected, with consequent additions to the projected budget and schedule for the project. Concerns were also expressed regarding the long term effects setting bed removal may have on the integrity of the vaults and the function of the embedded steel bar.13 While the client’s original concern was reliability of the repairs to the architectural tile, that concern was extended to the overall vault structure once work began in earnest on a larger area of vault than had been included in the mock-up and as the design team realized that it was more difficult to differentiate between architectural and structural tile.14

Pointing

Two original mortar formulations exist in the architectural tile of the original Guastavino tile vaults: “setting mortar” between the tile and a raised decorative surface or “pointing mortar.” A third mortar was used for the “structural” portion of the vault. This mortar acts as the “setting bed” or “bedding mortar” for the architectural tile; it was typically placed over the upper surface of the architectural tile and used to set the second layer of tile. The original installation of two mortars at the architectural tile appears to be the result of the construction technique of the vault system. In most of the vaults, the pointing mortar between the tiles is embedded into the setting mortar; the setting mortar is similarly embedded into the “setting bed” mortar. This suggests that the tile were laid on a rudimentary formwork typical of Guastavino tile construction, and the joints were filled with the setting mortar. Additional layers of tile were added above the architectural tile; these additional layers were placed in the “setting bed” mortar. Placement of the steel reinforcement within the vault layers, described previously, also supports this thesis about the vault construction. The raised decorative mortar was later applied to the soffit or inner face of the vaults after the structural tile was complete and the formwork removed; some of the setting mortar may have been removed to allow installation of the pointing mortar.

13 Guastavino generally used steel sparingly in their vaults and only where it was required to resist tensile stresses.

The results of the finite element analysis show tension developing at the pendentives of the sail vaults; the pendentives, which narrow to a point at the corners of the vaults, are not expected to carry load from the central, domical portion of the vault. Rather, load transfers to the arches that surround the vault at the point where the domical portion of the vault transitions to the pendentives.

14 The layer of architectural tile was lost in several vaults during the fire in 1997. These vaults were not, apparently, destabilized by the loss of this layer of tile and the use of Vanderbilt Hall was not restricted while repairs were made at the Oyster Bar. RSA have not modeled a vault with its thickness reduced by one layer; the effective factor of safety for a vault reduced in thickness by loss of the layer of architectural tile has not been established.


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The original raised mortar exhibits heavy fire and atmospheric soil and is chipped, friable, and disintegrating. In many areas, it is weakly adhered to the setting mortar between the tiles. Pieces of the pointing mortar could detach and fall at any time. The original mortars are now approximately 100 years old. The raised pointing mortar has exceeded its life expectancy and the setting mortar between the tiles is deteriorated. The support of the individual loose or hollow-sounding architectural tile is dependent on the integrity of the inner tile shell, which includes the original setting mortar between the tiles and the presence of a continuous field of tile. The setting mortar is much softer and more friable than the pointing mortar. Before installing any decorative pointing mortar, it is necessary to fully rake the joints to sound material and to a depth of at least ½-inch to enable keying of the new pointing mortar to the tile assembly and ensure the full depth of the mortar joint between the tile is sound, thereby forming a cohesive vault. Where original setting mortar remained below the ½-inch depth, it was sound and is expected to perform on a par with the new pointing mortar. Only one type of pointing mortar was used for the mock-up vault repairs because the original function of the setting mortar between the tiles is no longer necessary (Figure 9).15 Keying the raised pointing mortar between the tiles during a single material installation was considered to be more important than replicating the setting mortar and the relationship between the setting and pointing mortars, especially because it was now possible to do so with no formwork in place. A Restoration Design Focusing on Reliability

The discovery during the restoration of the Whispering Gallery that the steel reinforcing bars were more closely spaced and closer to the surface of the setting bed led, after much discussion, to a modification of the tile setting procedure. Previous tests showed that tile reset on an unmodified substrate passed the same adhesion tests as those tile set in a new mortar setting bed over a roughened substrate. However, setting tile on a new mortar bed on top of the original setting bed created a slight visual impact to the appearance of the vault in areas where the reset tile created an offset area. The resultant visual change to the vault appearance was negligible given that a wide range of offset tile in the original construction of the vaults is intrinsic in the design and is mostly concealed by the applied raised pointing mortar.16 The contractor suggested shaving the tile to maintain the original surface of the vault, control costs, and maintain the tight schedule. The Project Team considered the ability of the restored architectural tile layer of the vault to function as an independent shell in compression to be of paramount importance, and the construction schedule did not allow time to perform a full analysis of the impact of reducing the thickness of the 5/8” tile. Adhesion between the architectural tile and the structural tile could not be considered reliable in the long term, despite the results from the tests performed in the mock-up. The Project Team anticipated delamination, possibly induced by vibration (as noted above), would occur again in

15 Petrographic and chemical analysis of the setting mortar in the Oyster Bar indicates it is a non-hydraulic high-

calcium lime mortar with no gypsum. This is at variance with references that R. Guastavino Co. used quick setting mortar or “plaster” to set the architectural tile. The reason for the use of lime mortar as a setting mortar is not known, since it lacks quick setting properties.

16 The impact of resetting the tile with a greater offset was determined to not substantially impact the “whispering” acoustical effect within the vaults, which is dictated by the overall shape of the vaults. The acoustical properties remained intact after substantial quantities of debonded tile were removed from the vaults.


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the future. A repair that used shaved tiles and relied heavily on the adhesion of the architectural tile to the structural tile would not meet the client’s expectations for reliability. Therefore, shaving the backside of the tiles to allow re-installation of tile on a new mortar setting bed as suggested by the contractor was not considered consistent with the project goals. With the desire to produce the most reliable repair approach within the constraints of the ongoing construction, the Project Team concluded that there was less uncertainty involved in the function of the vault with tile of relatively uniform thickness in an offset configuration and no modified steel reinforcing than a vault with irregular areas comprised of thinner units. New mortar installed around the reset and stable tile left in place would re-establish a “cohesive” shell. BCA and RSA initially recommended three options for restoration of the ceiling vaults that focused on the reliability of the repairs based on the results of the laboratory analysis, field-testing, and mock-ups. All restoration approaches included the removal of all pointing mortar and the stabilization of all known loose tile in order to prevent potential hazards, such as falling materials. All approaches assumed that the mechanisms involved in the detachment of the architectural tile from the substrate, such as vibration within the Terminal, will continue to stress the vaults and over time cause future detachment.

• Option 1: Remove and reset all tile; replace broken and missing tile, and repair steel reinforcing, where necessary.

• Option 2: Remove and reset all loose tile and all ambiguous tile, as well as repair steel reinforcing, where necessary.

• Option 3: Remove and reset all loose tile and mechanically fasten all ambiguous tile that remain attached to the substrate after removal of perimeter joints.

Although Option 1 provided the least uncertainty by providing new setting materials at all locations, it was the most costly and it required the longest duration of restricted use or closure for the busy restaurant and Whispering Gallery passageway. Option 2 offered a low level of ambiguity as all loose and ambiguous tile were to be removed and either reset or replaced. However, removal of partially detached tile could result in the breakage and loss of some tile where the bonding was still partially sound. Option 3 was selected by the Owner for construction, even though it retained ambiguously attached tile and accordingly had lower expectation of reliability than the other two. It included the removals of all tile that could be removed with minimal effort, including ambiguously attached tile that either became detached during removal of mortar or adjacent tile, or were easily detached with hand tools, followed by the installation of concealed fasteners to secure all remaining ambiguous tile in place. This approach retained the most original tile in their existing locations and provided a shorter construction schedule. Testing demonstrated that the stabilization clips offered secondary support for ambiguous tile, securing them to the structural tile vault above. However, the Project Team preferred to minimize the number of ambiguous tile to the extent possible, thus limiting the amount of stabilization clips. Accordingly, the clips will be used only on the ambiguous tiles that resist removal efforts. The Guastavino vaults in the Oyster Bar and Whispering Gallery are unique in their combination of construction challenges. They are located in relatively small, but highly trafficked, spaces where the relatively low ceiling allows intimate viewing of original and repair materials. The original construction of the vaults, in distinct layers of tile and with embedded steel


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reinforcement, presented combined technical and aesthetic issues, sometimes not considered in the restoration of Guastavino assemblies in less accessible locations away from the public experience. The 100-year old tile and mortar joints are easily separated from their substrate and taken out of compression from their adjacent materials. The tile has withstood a fire. Partial post-fire restoration of the tile vaults resulted in sometimes unsuitable installations and surfaces that were not uniform in appearance. Between 2010 and 2012, the design, construction mock-ups, testing, and recent restoration of the Whispering Gallery Guastavino tile vaults aimed to resolve these issues and the potentially hazardous conditions presented by the loose tile and mortar, all the while bearing in mind the Owner’s desire for a long-term repair with high reliability. Addressing the above requirements while minimizing impact on the operations within the busy areas of the terminal during construction, with an eye toward preserving the original appearance of the Guastavino tile construction, the project team chose an overall restoration approach that included:

• Stabilizing all loose and ambiguous tile by removing and resetting as many as possible • Installing stabilization clips around ambiguous tile to remain • Re-establishing the cohesion and continuity of the architectural tile shell by repointing all

of the joints This approach establishes a stable assembly with the majority of the tile fully adhered to the structural vault with secondary support for the partially adhered (ambiguous) tile afforded by the stabilization clips. New mortar in the joints between all tile will allow the architectural tile to perform as an independent “cohesive” shell when the tile eventually detach from the substrate. In so doing, the restoration approach provides a very high expectation for extended stability of the architectural tile assembly while retaining a maximum amount of the original tile. This program balances the establishment of a stable system with reasonable longevity while minimizing disruptions to the operations of the restaurant and passageway and staying within budget.


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Figure 1. Typical vault in Whispering Gallery, with restored tile and mortar similar to that found in the Oyster Bar. Note the herringbone pattern at center of the vault comprised of ridged tile, and the smooth border tile.

Figure 2. Testing of the setting mortar’s load capacity. This test consisted of embedding 100-pound test fishing line in the setting mortar during its installation and attaching a bucket to the line, which was progressively filled with up to 35 pounds of weight.


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Figure 3. Two-prong stabilization clip installed.

Figure 4. Four-prong stabilization clip installed.


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Figure 5. Testing of the pullout capacity of the stabilization clips anchored into the structural tile. This test consisted of installing anchors with a partial embedment and leaving the clip legs proud of the tile; cast iron weights were then incrementally attached. The anchor to structural tile connection was tested to just more than 30 pounds, as shown here.

Figure 6. Two and four-prong clip configurations tested by ANA.


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Figure 8. Square steel bar stock placed in the “bedding mortar” between the architectural tile and the first layer of red clay structural tile, which was exposed during the mock-up in the Oyster Bar.

Figure 7. ANA testing of anchors embedded between tiles using a pulling device.


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Figure 9. Partially restored vault in the Whispering Gallery, with new mortar matching the

color of the historic mortar.

Documents

Approaching Total Reliability in Tile Repairs at the ...web.mit.edu/cron/Backup/project/guastavino/www/Koga-Oyster Bar.pdfApproaching Total Reliability in Tile Repairs at the Oyster