Thin Stone Marble Facade Systems

ISSUE 4/2010  V O L U M E 2 7  N U M B E R 4

Journal of architectural technology published by Hoffmann Architects, Inc., specialists in the rehabilitation of building exteriors. Thin Stone Marble Facade Systems

Juan Kuriyama, AIA and Stephanie L. Dillon, Assoc. AIA

Timeless, enduring, and stately, a time-consuming, disruptive, and marble has been used since ancient expensive endeavor. Greece and Rome for the most If you are considering thin stone important buildings of civilized society, marble for your building, or if you have from temples to bath houses to a building clad in marble panels, atten- markets. The expense of quarry- tion to fabrication, detailing, and signs ing and transporting the stone often of distress can make the difference constituted the bulk of construction between a minor repair project and costs, along with the workmanship of complete wall system failure. shaping and securing the heavy blocks. As the cost of labor increased, use of Material Properties and History marble came to be reserved for the most socially significant buildings, such Marble is a metamorphic rock that as courthouses and city halls. derives from the transformation of limestone and other sedimentary With technological advances in the last carbonate rocks under high heat and half-century, marble became avail- pressure. Unlike slate or mica, in able not only as traditional dimen- which differential stress creates planes sion stone, but as thin panel cladding. of cleavage, marble is non-foliated, As steel-framed structures grew in which permits its widespread use in popularity at the turn of the century, sculpture and construction. taller buildings changed the landscape of urban architecture. By midcentury, Hundreds of different types of marble marble veneers came into common are found throughout the world, New stone-cutting technology permits use as a curtain wall material, enabling including the United States, Europe, thinner marble panels—and brings new design wide availability at a fraction of the Egypt, and India. Characteristic veins challenges. cost of load-bearing stone. But marble and gradations in color result from panel wall systems are not without impurities in the limestone, which their drawbacks. move and re-crystallize as the stone metamorphoses into marble. Without the benefit of long-term performance testing, marble veneers In commercial applications, the term were installed at many buildings with “marble” may refer to a number of little understanding of the material’s geologic formulations, including true behavior over time. A number of calcite and dolomite marbles, as well these buildings have since required as travertine, serpentine, and hard partial or full wall system replacement, limestone, like Tennessee marble.

Juan Kuriyama, AIA, senior architect, and Stephanie L. Dillon, Assoc. AIA, project manager, develop building envelope solutions at Hoffmann Architects’ New York City office. They are specifically experienced in the design and rehabilitation of thin stone wall systems and marble structures. JOURNAL

Warping Fractures Spalls

The enduring presence of temples, ing an exacting attention to design, backup or to the structural frame by arenas, sculpture, and monuments engineering, and detailing. use of anchors. Selection of these from antiquity is a testament to the However, new developments in the anchors is critical to the performance durability of marble. However, while use of thin marble as a building materi- of the marble veneer. the physical properties and design al have opened up design options that When precast backup is used, stainless principles of dimension marble are were not possible with conventional steel hairpin anchors bonded into the time-tested, thin stone veneers don’t stone blocks. The textural richness of concrete are used to engage the back have centuries of refinement to guide marble can now be incorporated into of the marble panel. These pins are their fabrication, engineering, and curtain walls and shaped to achieve set on an angle, varying from 30 to 45 installation. In the 1950s, thin marble nearly any configuration. degrees. Each anchor should support was combined with large structural about two to three square feet of pre-cast concrete panels as a cladding To reap these benefits from the use wall panel, depending on weight and material. Due to its low cost, ease of thin stone marble veneers without anchor load tolerance. To protect of installation, and aesthetic appeal, falling victim to the material’s shortfalls, against cracks, anchors should be set the panels grew in popularity. Since consider intersections, terminations, about six to nine inches away from then, technologies for stone cutting, and physical properties of the selected panel edges, with no more than thirty anchorage, and detailing have evolved marble variety when reviewing design inches between them. considerably, offering owners more options, whether for new construction, options and better understanding of retrofit, or rehabilitation. Hand-set panels may employ anchors the causes and prevention of deterio- inserted into kerfs, which are narrow ration. Anchorage slots at panel ends, or fasteners set in There are two basic methods for thin holes at the sides or rear of the panel. Design and Installation stone installation: Care must be taken during fabrica- Considerations tion to cut kerfs and holes neither too • Hand-set method. Each stone is deep nor too shallow, so that they are The thinness that makes veneers so individually attached to the wall large enough to hold the anchor but economically appealing also makes framing system. not so large as to weaken the marble them more fallible than their conven- • Panelized installation method. panel. Incorrect placement too near tional dimension stone counterparts. One or multiple stone panels are the edge of the panel can cause Thinner marble is less resilient under factory installed on a steel frame the forces of changing temperatures, breakage. seismic loads, gravity, wind, and mois- or truss, or on a precast concrete Anchors should be engineered based ture. Connections require anchorage backup. The composite panels are on pull tests and calculations to systems far more sophisticated than then secured to the building frame withstand lateral and gravity loads. the metal fittings used to reinforce tra- as a unit. Where precast back-up is used, the ditional marble construction, demand- Panels must be secured to concrete thin stone veneer must be directly

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Cracks Sealant and anchorage failure Hysteresis connected with no annular (cavity) ally cut to a thickness of three or four Joint treatments are particularly criti- space between marble and concrete. inches. Developments in stone cutting cal in preventing moisture intrusion Relieving angles incorporated into the allowed for ever-thinner panels, with behind the panels, which can lead to anchorage system provide additional the 1970s seeing marble as thin as a heaving, displacement, and cracking. support. half inch. Lighter weight panels saved Water can also cause anchors to cor- money in materials and installation, but rode. Not only does this compromise Building Movement brought with them new problems. the strength of panel supports, the Marble, sealant, concrete and steel Thinner marble lacks the strength expansive forces of the deteriorating respond differently to changes in tem- to resist intrinsic material stresses. metal can crack the stone, creating perature, wind pressure, and seismic Through a process known as hys- further moisture entry points and ac- forces. Unless facade design antici- teresis, some fine-grained marble celerating the cycle of deterioration. pates and responds to these varying veneers gradually expand with each Controlling moisture egress through degrees of change, the wall system thermal change, resulting in perma- the appropriate use of flashings and will fail under the stress of restricted nent deformation. The interior and weep holes, which channel wind- movement. exterior faces of the stone expand at driven rain and condensation out of To improve tolerance for this differen- different rates, causing the panel to the wall system, are integral to the tial movement, a bond breaker, usually bow outward, away from the plane of durability of the facade. a polyethylene sheet or foam pad, may the wall. In turn, this warping causes be installed between marble panels stress on anchorage and perimeter Environment and concrete back-up. Likewise, joint systems. Rain water and rapid temperature accommodate movement at anchor Changes to the microstructure of the changes can cause detail deterioration points by drilling kerfs and holes marble also affect its permeability and and surface erosion. As the surface slightly larger than the anchor. contribute to micro-crack generation. of the marble deteriorates, bonds In the past, this anchorage space was Over time, the panel sustains not only between mineral particles in the often filled with epoxy to maintain deformation, but structural disintegra- marble weaken, and the stone’s flex- water-tightness. However, epoxies tion as well. ural strength, or ability to resist loads restrict shear movement, which can without deformation, can become cause the marble to crack. Instead, Moisture Intrusion compromised. The weakened marble opt for rubber grommets or flexible Hysteresis increases the porosity of becomes pitted at the surface, devel- sealants that balance the need for wa- marble, permitting additional moisture oping a characteristic texture known ter protection with the requirement to enter the panel. Damage to the as sugaring. At the same time, the for movement tolerance. marble from freeze/thaw cycling, salts, more porous surface admits still more acid rain, and pollutants then occurs water, compounding the problem. Hysteresis from the inside out, not just at the To extend the lifespan of marble Midcentury thin marble was gener- surface. veneers, clean thin stone facades

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periodically to minimize contaminants. Testing and Analysis Flexural strength tests may also be Depending upon the results of the conducted, both for existing marble initial inspection, the architect or en- and to evaluate potential replacement gineer may elect to remove panels to stones. identify concealed conditions and to Resolving Deterioration evaluate the properties of the marble. When developing a removal and test- Where wall cladding distress is ing program, the design professional observed, often in the form of cracks, should endeavor to remove sufficient displacement, bowing, or leaks, it is panels to provide a comfortable rep- important to address conditions resentation of the facade, and locate promptly. Emergency measures to panel removals accordingly. Tempo- prevent loose stone from falling, such rary protection or replacement is as face-pinning of marble panels, may also a consideration, so as to protect be necessary as a safety precaution. openings from the elements. Weather Ground-Penetrating Radar (GPR) identifies As research develops in the field of events and seasonal variables should anchor locations without removing panels. thin stone technology, new mechanical also be considered when scheduling and chemical treatments are becom- invasive testing. ing available to address hysteresis and loss of flexural strength, as well as to Removal of panels is disruptive, but promote resistance to moisture intru- it may be necessary to establish the sion and environmental stressors. marble’s physical condition and life expectancy, as well as to facilitate Visual Survey development of proper repair details. Depending on the height of the build- Typical laboratory tests include: ing, observation from street level using • Petrographic analysis (American binoculars may be a good place to Society of Testing and Materials start. However, use of a suspended / ASTM C1721) describes the scaffold or lift may be necessary for nature of the stone as regards its an accurate evaluation. In particular, lithology, mineralogy, morphology, hysteresis and other deterioration microstructure, and aging. within the stone may not be detect- Petrography enables classification able except by close examination of the marble and assists in the Replacement panel mock-up to assess and sounding, or tapping the stone to detection of defects. anchor geometry and installation protocol. assess its integrity. • Flexural strength testing (ASTM Using an accurate C880) indicates the stone’s ability set of drawings, to resist bending stress. Marble the architect or with higher flexural strength is less engineer should susceptible to hysteresis. label evidence of • Absorption (ASTM C503) tests damage, distress, the marble’s porosity, or tendency or failure. Visual to absorb moisture over time. survey provides an More porous stones tend to overall picture of sustain greater damage from the condition of the freeze/thaw cycling. marble wall system, such that remedial • Density (ASTM C503) indicates measures can be weight per unit volume. Different evaluated. classes of marble vary in Penthouse marble panel replacement in process. acceptable density for construction.

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The lightest, travertine, has a adhesion, while the stone should be or replacement stone. Sealant manu- minimum 144 pounds per cubic examined for cracks or spalls (areas facturers usually provide this service; foot, while the denser dolomite where the surface has broken away). however, testing by an independent must achieve at least 175 pounds Proper mortar adhesion is difficult to laboratory should be conducted per cubic foot. achieve, especially in high-rise applica- whenever possible. On-site testing commonly involves tions. To avoid water pooling in the Even if an appropriate joint compound measuring resistance to lateral forces joints, tooling profiles should provide a is selected, the system can still fail if produced by wind loading. Transverse path for moisture to drain. the space between panels is too small wind load tests simulate the vacuum to accommodate differential move- pressures that cause deflection and While some ment or too large for the sealant to bending, by subjecting marble panels “ span. Manufacturers’ guidelines and to increasing levels of force until the products do offer industry standards provide require- stone sustains permanent damage. ments for width-to-depth ratios and Planning for pull tests requires wind improved resiliency, minimum bond surfaces. load analysis to determine necessary Repair load values and factor of safety. they are not a Although displaced, de-bonded, or Wind Load Design heavily bowed panels will require replacement, it is possible to restore Most building codes provide prescrip- replacement for marble that has sustained only minor tive requirements regarding wind damage. This is good news both loads on building components and correct design and from a preservation point of view cladding, which vary depending upon detailing.” and from a practical one. With many building height. The American Society quarries closed or depleted by the of Civil Engineers (ASCE) 7 standard late twentieth century, finding suitable For the more commonly used joint is currently considered state-of-the- replacement marble can be expensive sealants, the design professional should art for determining design loads on or even impossible. structures. Note that some older consider properties such as adhesion building codes do not consider ASCE (bonding to the stone), cohesion (re- After evaluating information gathered 7, which could be significantly more sisting internal cracking), and flexibility. during the visual survey, the design professional should locate and catalog conservative than the code require- The sealant should resist moisture each deficiency. Small spalls less than ment. For this reason, it is important ingress and thermal degeneration, half a square foot and small cracks less for the architect or engineer to evalu- while providing enough tolerance for than a foot long can be repaired with ate all applicable codes and standards, marble panels to move in response to patching material. Granular matter, in order to provide the building owner changes in temperature and pressure. including marble dust, can be added with recommendations. Adhesion tests should be performed to determine the appropriate product to improve the match in texture Another method for determining load for the marble composition, as well as and color. Behavior of the patching compound in response to heat, UV values is a wind tunnel analysis, per- to evaluate whether or not a primer is radiation, moisture, cold, and pressure formed in a laboratory. While this ap- necessary. proach can provide more accurate val- must be considered, so that the mate- ues tailored to the shape and location In general, silicones have a better rial is neither so rigid as to restrict of the building, the cost to perform performance record than do poly- the movement of the marble nor so the analysis might be prohibitive. urethanes, which tend to revert to an pliable as to fail when exposed to the uncured condition. However, silicones elements. Perimeter Waterproofing collect more dirt, such that light colors If cracks or spalls are large or close to Typically, thin stone marble panels are will turn dark over time without dili- the edges of the stone, a “Dutchman” joined at the perimeter with sealant, gent cleaning. repair may be used. The damaged although mortar has also been used. Research and testing should be con- area is removed, and a new piece, or If the latter is the case, joint mortar ducted to verify that the product and “Dutchman,” is installed with appropri- should be evaluated for strength and primer selected do not stain existing ate anchors.

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the Marble Institute of America’s which may be problematic if Dimension Stone Design Manual. In the structure already abuts the general, the type of marble, its weight property line. and thickness, and the composition • Presence of hazardous materials. and exposure of the structure should Where testing reveals PCBs in dictate the appropriate safety factor sealant or asbestos in insulation and anchorage method. or adhesives, removal of the Re-Cladding existing curtain wall may be cost- prohibitive. Where inadequate design, faulty installation, or widespread deterioration • Energy efficiency. Unlike their precludes repair of individual panels, load-bearing cousins, thin marble complete replacement may be a viable panels provide little insulating value. Thermal performance of stone Face-pinning is often used as a safety mea- option. Many cases exist of thin stone sure to prevent loose panels from falling. wall systems that have failed prema- veneers is derived primarily from turely, and the building is stripped of insulation in the cavity or backup Larger, continuous cracks should be the marble panels and clad with new wall. Newer systems are designed evaluated on a case-by-case basis. material. Re-skinning the facade is a for improved energy efficiency, Usually, face-pinning the stone and drastic and expensive approach, but which may help to offset the cost patching the crack is sufficient. How- for buildings exhibiting extensive fail- of rehabilitation or replacement. ever, multiple cracks on a single panel ures, it may be the only feasible tactic. • Aesthetics. Marble’s sculptural could be symptomatic of restraint quality and depth of light Evaluating the Options and hysteresis stresses, which might penetration makes it an require replacement of the panel and Before rushing to a decision, consider aesthetically satisfying building possibly the anchoring system. the technical viability and anticipated material. Replicating this effect return on investment for each option, with patches or replacement Structural Considerations including repair, isolated replacements, panels can be difficult, and care Marble panel systems are a type of anchorage rehabilitation, and re-clad- must be taken to mimic the curtain wall cladding, which does not ding. Some factors to consider: gradations and texture of the bear any building load other than its • Condition of the existing original stone as closely as possible. own weight. This weight must be substrate. If the back-up or Likewise, full replacement of a transferred via anchors, and some- framing exhibits deterioration, marble facade demands thoughtful times through secondary supports, to it may be necessary to remove consideration, as the finished the building’s main structural system. panels and repair the source of appearance of the building can Additional loads from wind, seismic, distress. Fixing cracks or replacing alter dramatically. impact, construction, and other forces sealant won’t help unless the When analyzing cost estimates, must also be considered in the an- underlying problem is resolved. consider not only the up-front price chorage system design. • Load capacity. Replacing very thin of repair or replacement, but the Due to hysteresis, anchorage details marble panels with thicker ones long-term expense incurred through must consider the change in shape of can resolve hysteresis issues, but maintenance and repair. Properly the marble as it ages. Therefore, new may cause structural problems constructed marble wall systems re- or replacement anchors must not only if the framing can’t handle the quire comparably less maintenance contain the stone panel within the ex- increased weight. than do many other types of curtain terior wall assembly and comply with • Space between cladding and walls. Sealant replacement every 10 code requirements for lateral forces, property line. A cost-effective to 20 years is usually the only major they must also remain flexible enough strategy for facade upgrades anticipated repair, depending on the to tolerate movement. can involve retrofitting a new type of sealant used. ASTM C1242 provides guidelines for curtain wall over existing framing. Whether choosing rehabilitation or re- the selection, design, and installation However, the building face then placement, establish a routine cleaning of stone anchoring systems, as does moves outward by several inches, program to remove stains and con- (continued on page 8)

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Thin Stone Veneer MasterCard Headquarters Purchase, New York Solving stone panel distress demands Travertine and Concrete Facade technical know-how, practical experi- Rehabilitation ence, and aesthetic sensibility. When it comes to resolving anchorage, clad- Verizon Building ding, or structural framing problems, 240 E 38th Street Hoffmann Architects has the expertise New York, New York to get the job done. Our architects Granite Veneer Facade Repair and engineers diagnose and correct deficiencies related to the unique ma- Ralph S. O’Connor Recreation Center terial properties and design challenges Johns Hopkins University of stone veneers. Baltimore, Maryland Limestone Panel Investigation Hoffmann Architects has developed thin stone wall system solutions at Bristol Myers Squibb Pharmaceutical diverse properties, including: Research Institute Wallingford, Connecticut Chase Manhattan Bank Stone Panel Anchorage Rehabilitation New Rochelle, New York Marble Panel Investigation Office Building 110 South Bedford Road One Shell Square Corporate High-Rise at 1095 Avenue Mt. Kisco, New York of the Americas in New York, New York. New Orleans, Louisiana Marble Panel Facade Rehabilitation Marble and Glass Curtain Wall Consultation. Marble Panel Failure Consultation

The Phoenix Companies Headquarters Hartford, Connecticut Limestone Panel Rehabilitation School of Law Library University of Connecticut West Hartford, Connecticut Granite Veneer Stabilization

Office Park 333 Westchester Avenue White Plains, New York Marble Panel Consultation

Crowne Plaza Hotel Times Square New York, New York Blessed Kateri Tekakwitha Parish in Sparta, New Jersey. Thin Stone Veneer and Roof Granite Panel Replacement Rehabilitation.

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Hoffmann Architects, Inc. 2321 Whitney Avenue Hamden, CT 06518

ADDRESS SERVICE REQUESTED

(continued from page 6) posed by this natural material in the built environ- JOURNAL is a publication of Hoffmann ment. Architects, Inc., specialists in the rehabilitation building exteriors. The firm’s As more research is con- work focuses on existing structures, di- ducted into the relatively agnosing and resolving problems within recent field of thin stone roofs, facades, windows, waterproofing wall systems, products materials, structural systems, plazas/ter- races, parking garages, and historic and continue to emerge on landmark structures. We also provide the market that claim to consulting services for new building improve resistance to en- construction, as well as litigation and vironmental contaminants, claim support. moisture penetration, For address changes, free subscriptions, temperature fluctuations, or information on the topics discussed hysteresis, differential in this issue, contact our Marketing Periodic sealant replacement should be part of a movement, UV radiation, Coordinator at 800-239-6665, comprehensive maintenance program. and other stressors. Some [email protected], or: taminants, without being so aggressive have contributed to improvements in 2321 Whitney Avenue as to damage the stone. Due to thin stone veneer construction; others are Hamden, CT 06518 marble’s propensity toward hysteresis, basically worthless. 203-239-6660 periodic inspection of the wall panels As with any new technology yet to 1040 Avenue of the Americas, Ste. 14C is recommended to evaluate loss of stand the test of time, treatments strength. Many of the problems inher- New York, NY 10018 claiming to resolve deficiencies in 212-789-9915 ent to thin stone marble wall systems design or material properties should can be avoided through appropriate be treated with caution. While some 2611 Jefferson Davis Highway, Ste. 200 maintenance and early detection. products do offer improved resiliency Arlington, VA 22202 703-253-9800 in marble panel systems, they are not The Future of Stone a replacement for correct design, wa- www.hoffarch.com Thin stone veneers offer the aesthetic terproofing, and detailing. To avoid the benefits of traditional load-bearing expense and inconvenience of repeat Editor: Alison Hoffmann Production: Cari Tate stone at a more affordable price. As repairs—some of which can actually the industry develops, more buildings cause permanent, irreversible damage have come to adopt this technol- to the marble—work with your design ogy. For thin marble cladding to last, professional to investigate, resolve, and, however, it is necessary to understand ideally, prevent underlying problems, and address the particular challenges before reaching for a quick fix.