Manufactured Stone Veneer: Common Pitfalls in Design and Installation Patricia Aguirre, REWC, PE, CDT Bristow, VA tricia@tros.org Matthew Innocenzi, RBEC, PE Nick Innocenzi & Sons Consulting Engineers and Associates, LLC Warrenton, VA minnocenzi@niscea.com IIBEC International Convention & Trade Show | SeptembeBEr 15-20, 2021 A AgUIrre and | 221 Patricia Aguirre, REWC, PE, CDT Bristow, VA Patricia Aguirre is a building enclosure consultant in northern Virginia. Her work focuses on forensic field and laboratory investigations; façade and building enclosure investigations; structural inspection, analysis, and design; architectural retrofit and repair; and development of design documents and repair recommendations. Aguirre is an active member of IIBEC, serving on the REWC Exam Committee and teaching several exterior wall-related courses. She also serves on ASTM C11 committee on Gypsum and Related Building Materials. Matthew Innocenzi, RBEC, PE Nick Innocenzi & Sons Consulting Engineers and Associates, LLC | Warrenton, VA Matthew Innocenzi is the principal of his firm. He has over 20 years of experience as an engineering consultant, with a focus on litigation support and expert testimony for building enclosure systems, particularly light-gauge metal framing, Portland cement stucco, brick veneer systems, steep-slope roofing materials, and waterproofing. Innocenzi is also an active member of ASTM C11 and D08 committees on Gypsum and Related Building Materials and Systems and Roofing and Waterproofing, respectively, and serving as chair and technical contact for ASTM C926, Standard Specification for Application of Portland Cement-Based Plaster and ASTM C1860, Standard Test Methods for Measurement of Tensile Strength or Bond Strength of Portland Cement-Based Plaster by Direct Tension task groups. 222 | Aguirre and Innocenzi II BEC International Convention & Trade Show | September 15-20, 2021 ABSTRACT SPEAKERS Adhered masonry veneer (often referred to as manufactured stone veneer, or MSV) has been growing in popularity and use throughout North America over the past 20 years. MSV offers the beauty of masonry with the cost efficiency and reduced weight of stucco. In addition to specific manufacturers’ instructions, current codes and industry standards that govern its design and installation include ICC-promulgated model building codes, masonry codes (TMS 402 and TMS 602), ASTM standards, and Masonry Veneer Manufacturers Association (MVMA) publications. Simply referencing these published code and industry standard documents in drawing notes, project manuals, or contracts is often insufficient, leading to improper design and installation techniques that ultimately result in failure. This paper presents some of the common design and installation pitfalls associated with MSV to help designers and installers enjoy a more successful, durable application. This presentation is targeted at an intermediate audience of designers, installers, and building owners. Manufactured stone veneer (MSV) has its roots in portland cement plaster (stucco). As will be discussed in greater detail in this paper, an MSV system is similar to stucco, as both MSV and stucco systems share a base coat (that is, scratch coat and brown coat) behind the finish coat. While adhered tile cladding systems have been in use since ancient Egypt, some of the early concepts of modern MSV can be traced back to the early 1950s via Garden State Brick. Named after New Jersey, where it was innovated and commonly used, Garden State Brick featured the use of a simulated brick template that was stamped into an oversized stucco finish coat, leaving the impression of perfectly laid brick coursing with the economic benefit of plaster. (Garden State Brickface and Siding, formed in 1953, innovated the technique and created the formulations for the proprietary system that is still in use.) In more recent times, cultured (faux) brick or stone or “thin” brick (actual brick units shaved into ¼-in.-thick sections) would ultimately become the finish coat that, applied on top of the base coat, formed the MSV system. While MSV has been in use for nearly 70 years and was first included in a building code in 1967, it was not until 2009 that a detailed installation guideline was issued.1,2 Even currently, the design standards are confusing, as the MSV system is a hybrid of both stucco and masonry. The following sections of this paper discuss the building code requirements and industry standards that govern the application of MSV. BUILDING CODE REQUIREMENTS The International Building Code (IBC) and International Residential Code (IRC) contain general requirements for exterior wall assemblies that apply to MSV assemblies. In particular, the IBC and IRC contain the following as they relate to exterior drainage wall assemblies (direct-applied applications are outside the scope of this paper):3,4 • Exterior drainage walls are to include at least one layer of a water-resistive barrier (WRB) and flashings located at interruptions in the vertical plane to divert water to the exterior. • Where plaster (including the base coats for MSV systems) is applied over wood-based sheathing, a performance equivalence of two layers of Grade D paper for residential construction or a WRB meeting ASTM E2556, Type I, for commercial construction is required. Alternatively, one layer of WRB with resistance equal to or greater than Grade D paper (residential construction) or a single layer of WRB meeting ASTM E2556, Type II (commercial construction), can be used if the base coat is separated from the WRB via an intervening non-water-absorbing drainage layer or airspace, such as in a rainscreen system. An additional exception for commercial construction permits a single layer of WRB where a ventilated airspace is provided between the stucco and the WRB for installations in Climate Zones 1A, 2A, and 3A. • When using multiple layers of WRB, each individual layer of WRB is to be lapped independently. • The WRB is to lap over the designated drainage screed or flashing. • Designated drainage screeds are to be located a minimum of 4 in. above earth, 2 in. above paved surfaces, and ½ in. above exterior walking surfaces supported by the same foundation that supports the exterior walls (for example, balconies and patios). In addition to the general exterior wall requirements highlighted previously, the IBC and IRC also incorporate requirements from other publications through reference. These include references to TMS 402, Building Code Requirements for Masonry Structures, and TMS 602, Specification for Masonry Structures, as well as to various standards promulgated by ASTM International (ASTM). These building codes and specifications provide requirements for WRBs, flashing, and weeps as well as structural requirements, such as the accommodation of differential movements, structural support (gravity and lateral loading), and height limitations and considerations. (Manufacturers’ requirements specific to proprietary systems may differ from those explicitly prescribed in the model building codes and referenced standards. Such deviations may be permitted through approval by the building official or other authority having jurisdiction under the alternative materials provisions in the code. A discussion of such proprietary systems is outside the scope of this paper.) Key prescriptive requirements in the masonry codes and standards as they relate to MSV include the following:5,6 • The size of the veneer unit is to have a face area of no greater than 5 ft2, a weight no greater than 15 lb/ft2, and dimensions that measure no greater than 36 in. in height and length and no greater than 25/8 in. in thickness. • The height, length, and wall area are unlimited except as required to accommodate differential movement. • Backing for MSV can be masonry, concrete, or metal lath and portland cement plaster. • The adhesion of MSV must have at least 50 psi in shear strength when tested in accordance with ASTM C482. Alternatively, the face units are to be adhered in compliance with Article 3.3C of TMS 602. The prescriptive requirement to adhere face units in accordance with Article 3.3C of TMS 602 warrants further discussion. This article of the specification refers to model building code provisions for metal lath and portland cement-based plaster. It also refers to ACI 524R, Guide to Portland Cement Plastering, for information on lath and accesII ii B E C International Convention & Trade Show | September 15-20, 2021 A Aguirre and Innocenzi | 223 Manufactured Stone Veneer: Common Pitfalls in Design and Installation sories and their installation. Article 3.3C also refers to the model building codes and ACI 524R for recommendations to control cracking. In turn, ACI 524R references stucco standards ASTM C926, Standard Specification for the Application of Portland Cement-Based Plaster (Stucco), and ASTM C1063, Standard Specification for Lathing and Metal Accessories.7 As can be inferred from their titles, ASTM C926 and ASTM C1063 are standards that provide the minimum design and application requirements for stucco systems. It is noteworthy that ASTM C926 and ASTM C1063 are prescriptive standards and not performancebased. The completed system conforming to these prescriptive requirements is therefore deemed to comply with building code requirements. Examples of key prescriptive requirements found in ASTM C926 and ASTM C1063 that are pertinent to base coats of MSV systems include the following:8,9 • Preparation of the base coat substrate • Proportioning and mixing requirements for the scratch and brown coats • Nominal thickness requirements of the scratch and brown coat • Application and curing requirements • Lath and accessory material and fabrication requirements • Lath and accessory fastening requirements • Lath laps • Control joint layout requirements as follows: — Maximum spacing of 18 ft — Maximum panel size of 144 ft2 (for vertical applications—that is, walls) — Maximum panel length-to-width ratio of 2½ to 1 INDUSTRY STANDARDS Although not code requirements, several industry standards have been published to provide guidance regarding the design and installation of MSV. In 2009, the Masonry Veneer Manufacturers Association (MVMA) first published a guide that summarized best practices for the WRB, lath and accessory materials and their installation, scratch coats, mortar mixtures, surface preparation, and veneer installation. This guide also included schematic detail drawings for typical conditions at corners, transitions, and terminations.2 Since 2009, MVMA has updated and reissued its guide several times, with the two most recent editions (the fourth edition in 2014 and the fifth edition in 2017) issued by MVMA as an affiliate of the National Concrete Masonry Association (NCMA). The title of these last two editions was revised to Installation Guide and Detailing Options for Compliance with ASTM C1780, ASTM C1780 being a new consensus- based standard that was first released in 2013. The most recent revision of ASTM C1780, Standard Practice for Installation Methods for Cement-Based Adhered Masonry Veneer, issued in 2020, refers back to the MVMA installation guide document and reiterates much of the same information but does not include the schematic detail drawings. Guidance is provided for both interior and exterior applications. Important provisions in this ASTM standard for exterior applications include the following:10 • Two layers of WRB are required over all sheathing except where the local building code permits otherwise. • Foundation weep screeds and lath are to be installed in accordance with ASTM C1063. • Stucco scratch and brown coats when used as the MSV scratch coat are to meet ASTM C926 up to the brown coat without the application of the finish coat. MSV scratch coats are required to be a minimum of ½ in. thick, which differs from the ASTM C926 requirement for scratch and brown coats to be a total of ¾ in. thick (nominal) for application over lath. • Mortar is to be either Type N or Type S in accordance with either the property or the proportion specification of ASTM C270 or ASTM C1714. Mortars meeting ANSI 118.1, 118.4, or 118.15 are also permitted. • Cement backer board located outboard of the WRB and sheathing is a permissible substrate for MSV installation. Specific surface preparation instructions for this assembly are provided. • Assemblies incorporating continuous insulation are not addressed within ASTM C1780; however, direction is provided in the referenced MVMA guide. • Generally, MSV units are to be applied to the scratch coat after the scratch coat is thumbprint hard. The scratch coat is to be damp, but no free water is to be present on its surface. • Units are to be set in a full setting bed mortar that is either applied directly to the prepared backing surface (for example, scratch coat or cement board) or applied to the unit itself using the “back butter” method. Full coverage of the unit and full contact with the setting bed, unit, and prepared surface are required. The overall thickness of the scratch coat and mortar setting bed is limited to a maximum of 11/4 in. • Mortar is required between units, even in “tight fit” joint applications, such as 224 | Aguirre and Innocenzi II BEC International Convention & Trade Show | September 15-20, 2021 As can be inferred from their titles, ASTM C926 and ASTM C1063 are standards that provide the minimum design and application requirements for stucco systems. It is noteworthy that ASTM C926 and ASTM C1063 are prescriptive standards and not performance-based. The completed system conforming to these prescriptive requirements is therefore deemed to comply with building code requirements. those that are intended to provide the appearance of dry-stack masonry. • Movement joints (control and expansion joints) are not directly addressed in the standard. However, the standard does refer to other industry standards as follows: — The standard references TMS 402, which requires the veneer to be designed and detailed to accommodate differential movement.5 TMS 402 does not offer any further guidelines or requirements on how to accommodate the differential movement; rather, that is left to the discretion and judgment of the design professional. — Installation of lath and foundation weep screeds is to be performed in accordance with ASTM C1063, which itself provides prescriptive requirements for control joint installation. However, the MSV standard does not mention the term control joint, so it is reasonable to conclude that the control joint spacing requirements provided in ASTM C1063 are not necessarily incorporated by reference. — The referenced MVMA guide states that “consideration should be given to where differential movement is expected.”11 The current printing refers to NCMA’s website for more information. Previous printings of the current edition of the MVMA guide referred to an article titled “Are Control Joints Needed with Adhered Concrete Masonry Veneer?” that is no longer available from the MVMA/NCMA website;12 this reference is not included in the current printing of the current version of the guide. The article makes the argument that, unlike stucco, the joints between masonry units in MSV effectively act as control joints. It concludes that control joints at spacings mandated in ASTM C1063 are not justified, although movement joints should be located to coincide with expansion joints in the substrate. The article indicates that study of this issue was ongoing to determine what, if any, practical limits should be implemented for constructing oversized panels.13 The copy of the article the authors were able to locate was dated October 2011; it is unknown whether this subsequent study resulted in a revision to MVMA’s position regarding control joints. • The annex provides much-needed modifications to the shear bond test method in ASTM C482. The unmodified version is a tile test that uses a standard mortar and substrate to test the bondability of the adhered unit. The modifications in the annex to ASTM C1780 instead test the shear bond of the actual assembly using the masonry unit, mortar, scratch coat, and substrates that the system is to use during field work. However, the samples are still to be prepared and cured under laboratory conditions, which may not reflect actual construction or exposure. In addition to the consensus-based ASTM C1780 standard and the industry group MVMA guide, other industry associations have provided guidance for material-specific adhered veneers. These include Brick Industry Association (BIA) Technical Note 28C for thin brick; NCMA TEK 3-6C for concrete masonry veneers; Thin Veneer Installation Guide, published by the Indiana Limestone Co. (ILC) for Indiana Limestone veneers, and Adhered Natural Stone Veneer Installation Guide, published by the Rocky Mountain Masonry Institute (RMMI) for other natural stones. Items of interest within these industry standards include the following: • Thin brick can be installed via either (1) the thick set method, which employs a scratch coat installed over lath; (2) the thin set method, in which the thin brick unit is adhered directly to the substrate (consisting of either cement board, masonry, or concrete) with a thin (approximately 1/8 in. thick) layer of adhesive or modified mortar; or (3) as a modular panel or prefabricated panel system.14 The thick set method is nearly identical to the method described in ASTM C1780. • ILC provides instructions for installation of thin stone veneer over continuous insulation, while RMMI advocates against such installations, as the rigid insulation does not have enough rigidity to resist crushing under applied loads (such as from a ladder leaned against the completed veneer). The insufficient rigidity could, in turn, result in cracking of the stones.15,16 Neither BIA nor NCMA addresses assemblies with continuous insulation.14,17 • Movement joints are recommended for thin brick and natural stone products, even though RMMI notes that natural stone tends to be relatively dimensionally stable. BIA, ILC, and RMMI provide detailed direction regarding the spacing and construction of movement joints. For thin brick, these recommendations mirror the requirements for control joint spacing given in ASTM C1063.9,14 The recommendations for stone vary, but generally include locating movement joints at openings, near building corners, between dissimilar materials, and within large expanses without openings.15,16 • NCMA’s stance on movement joints in adhered concrete masonry veneer is less clear. TEK 3-6C provides information for both anchored and adhered veneers. As a design consideration that is applicable to both types of veneer, it states, “[C]ontrol joints should generally be placed in the veneer at the same locations as those in the backing, although recommended control joint spacing can be adjusted up or down based on local experience, the aesthetic requirements of the project, or as required to prevent excessive cracking.” It refers to another publication for additional information on this topic: TEK 10-4, “Crack Control for Concrete Brick and Other Concrete Masonry Veneers.”17 While adhered concrete masonry veneer would appear to be one of these “other concrete masonry veneers,” the dimensions of the units described in the publication all exceed the thicknesses permitted by code for adhered units. Assuming that adhered concrete masonry veneers do fall under the umbrella of “other concrete masonry veneers” within the purview of this document, control joints are recommended at locations of stress concentrations with a maximum spacing of 20 ft and a maximum panel ratio for length to height of 1½.18 Table 1 provides a comparative summary of the industry standard requirements discussed above. II ii B E C International Convention & Trade Show | September 15-20, 2021 A Aguirre and Innocenzi | 225 COMMON DESIGN AND INSTALLATION ISSUES The following section of the paper provides examples and case histories of common design and installation pitfalls associated with MSV. While this section is not intended to provide a comprehensive examination, it is the authors’ intent to raise awareness of these common problems and offer ways to avoid them in practice. Improper Integration of WRB, Accessories, and Flashings As is common with any drainage wall assembly, problems with the design and installation of the WRB, accessories, and flashings can lead to devastating consequences, including water infiltration, microbial growth, curtailed service life of the exterior walls, and occupant discomfort. The IBC and IRC clearly require flashings in exterior walls at specific locations, such as perimeters of windows and doors; penetrations and terminations; exterior wall intersections with roofs, chimneys, porches, decks, and balconies; and other locations where moisture can enter the wall. Failure to properly integrate the WRB with the flashing can undermine the performance of the flashing to the point that it would be completely useless. The most common manner in which the WRB is not properly integrated with the flashing is a reverse lap where water is directed behind the flashing. An example of this condition is represented in Fig. 1, where reverse laps were observed between the WRB, consisting of a paper-backed metal lath installed over a liquid-applied material, and the base of wall flashing. Often, reverse laps between the WRB and the flashing (or between individual layers of sheet WRB) can also direct water behind the WRB, where it is subject to damaging the surface of the exterior sheathing. MSV is particularly vulnerable to water damage; although the system itself is relatively 226 | Aguirre and Innocenzi IIiiBEC International Convention & Trade Show | September 15-20, 2021 Component MVMA/ASTM C1780 BIA TN 28C NCMA TEK 3-6C ILC RMMI Continuous insulation Not addressed* Not addressed Not addressed Guidance provided Not recommended Mortar/base coat ASTM C270 Type N or S; ASTM C1714 Type N or S; ANSI A118.1, A118.4, A118.15 ASTM C270 Type S (with or without latex or polymer modifier) or ANSI A118.4 Follows TMS 402/TMS 602 requirements ASTM C270 Type S Type N or Type S (presumably ASTM C270) Drainage Two layers WRB and weep screed per ASTM C1063 References IBC and IRC requirements References IBC requirements for weep screeds; indicates that backing system must be designed and detailed to resist water penetration References building code requirements Single layer of building paper with flashing at base of walls Setting-bed application Full setting bed either applied to the scratch coat or “back buttered” to the unit itself Thick set per ASTM C1780, thin set with 1/8 in. setting bed, or modular/prefab system Follows TMS 402/TMS 602 requirements Back buttering of masonry units with reference to ASTM C1242 Full setting bed applied to the scratch coat Movement joints No guidance provided Follows ASTM C1063 20 ft or length-to-height ratio of 1.5:1 At openings, at changes in materials, and where movement is anticipated in backup construction; near outside corners; references ASTM C1242 and The Building Stone Institute for maximum spacing recommendations (15 ft and 30 ft, respectively) At openings and changes in materials, near corners, and at approximately 35 ft o.c. in walls without openings Table 1. Comparative summary of industry standard requirements * Not addressed in ASTM C1780, but direction is provided in the referenced MVMA guide. Note: BIA TN 28C = Brick Industry Association (2014); IBC = International Building Code; ILC = Indiana Limestone Co. (2016); IRC = International Residential Code; MVMA/ASTM C1780 = Masonry Veneer Manufacturers Association (2009); NCMA TEK 3-6C = National Concrete Masonry Association (2012); o.c. = on center; RMMI = Rocky Mountain Masonry Institute (2010); WRB = water-resistive barrier. 1 in. = 25.4 mm; 1 ft = 0.305 m. unaffected by water, when installed over weather-sensitive materials (particularly wood-based sheathing), the associated swelling and volumetric changes of the underlying material(s) can exert forces on the veneer, resulting in cracks, spalls, and pop-offs. Examples of this condition are provided in Fig. 2. In the authors’ experience, a rainscreen assembly is the most effective means of collecting and discharging water that penetrates the MSV. Effective drainage design and installation are key to avoiding the detrimental effects of water. To a lesser extent, two layers of WRB properly lapped and integrated with flashings can be used; however, consideration should be given to the scores of fasteners that will ultimately penetrate the WRB during installation. Insufficient Embedment of Lath As discussed previously, MSV is often composed of a cementitious base coat installed on top of lath. Until about 2015, metal was the predominant (and only) material used for lath. (While metal lath is most common, nonmetallic laths are readily available with the development of ASTM C1787 and 1788.) A common challenge with lath—particularly expanded metal, or diamond, lath—is embedment within the plaster matrix. It is well known that MSV is not waterproof and allows water to penetrate through the veneer to the WRB. As water penetrates through the veneer, it comes into contact with the metal lath. In conditions where the lath is not protected by the plaster matrix, and especially in brackish and coastal environments, the lath is subject to corrosion. In turn, corroded lath can cause the MSV system to spall, or pop off the wall, because of the expansive forces associated with the corrosion. Examples of this phenomenon are provided in Fig. 3 and 4. Moreover, corroded lath can also lead to compromised lath attachment to the backup wall and present a risk of falling debris. In most instances, improper embedment of the lath is the result of poor workmanship—such as, poor troweling and insufficient base coat thickness. However, even with the best of application techniques, it is noteworthy that complete embedment of lath is nearly impossible to achieve in the field. Screws, nails, and staples used to fasten the lath to the substrate pinch the lath tightly against the backing material, making it impossible to achieve complete embedment II ii B E C International Convention & Trade Show | September 15-20, 2021 A Aguirre and Innocenzi | 227 Figure 1. Example of reverse lapped WRB materials in an MSV system. Note: MSV = manufactured stone veneer; WRB = water-resistive barrier. Figure 2. Poorly integrated/installed water-resistive barrier and flashing behind manufactured stone veneer allowed for significant water intrusion, damage, and swollen substrates. Figure 3. Poorly embedded lath and associated corrosion. Figure 4. Poorly embedded metallic lath resulted in corrosion, pop-offs, and compromised anchorage. in all locations. In the authors’ opinion, consideration should be given to materials that are not sensitive to corrosion, such as nonmetallic laths and stainless steel, particularly in highly corrosive, brackish environments. Failure to Account for Anticipated Movements A common pitfall in the design of MSV is the failure to appropriately account for and accommodate differential movements. This is most commonly found when the MSV is applied over dissimilar backing materials, such as cast-in-place concrete and wood framing. With the advent and growing popularity of wood-frame over podium-slab construction, this problem has likewise grown in frequency and severity. An example of this condition is presented in the detail in Fig. 5. As can be seen from this detail, a continuous application of MSV was designed over dissimilar backing materials: namely, wood-framed exterior walls and bulkheads and the edge of a concrete podium slab. No means to accommodate differential movement were called out in the detail or provided in the finished construction. After construction, widespread cracking, bulging, and delamination were noted in this area (Fig. 6). Test cuts performed in the existing cladding revealed no provisions for differential movement, discontinuous lath, and poor bond between the MSV base coat and the concrete slab edge (Fig. 7). As is well known and documented in the industry, wood-frame construction undergoes considerable shrinkage with time. In the absence of joints to relieve the downward movement of the wood-framed exterior walls, the MSV compressed at the slab edge, leading to the observed cracking, bulging, and delamination. In addition to the differential movements anticipated between dissimilar substrate materials, the MSV also needs to be designed and constructed with movement joints to accommodate movement within the veneer itself, due to shrinkage (or in the case of thin brick, expansion) of the MSV units, the shrinkage of the underlying cementitious mortar and scratch coats, and thermal cycling. Although ASTM C1780, MVMA’s guide, and NCMA’s TEKs do not directly address the inclusion of control joints for these purposes, it is the authors’ opinion that such joints are necessary, particularly in long expanses of veneer that can occur on commercial buildings. Such joints should be located as directed in ASTM C1063 and summarized earlier in this paper. Failing 228 | Aguirre and Innocenzi IIiiBEC International Convention & Trade Show | September 15-20, 2021 Figure 5. Sample detail indicating continuous application of MSV over dissimilar materials. Note: MSV = manufactured stone veneer. 1″ = 1 in. = 25.4 mm; 1′ = 1 ft = 0.305 m. Figure 6. Cracking noted in manufactured stone veneer in area that correlated with dissimilar backup materials. Figure 7. Test cut over bulged and cracked MSV revealed continuous application of MSV without provisions for differential movement between framed exterior walls and concrete podium slab. Note: MSV = manufactured stone veneer. to provide these movement joints can result in cracking, such as that exhibited in Fig. 8 and 9. Insufficient Coverage on Back of Units As previously discussed, ASTM C1780 requires that MSV units are to be set in a full setting bed mortar that is either applied directly to the backing surface or applied to the unit itself using the “back butter” method. Full coverage of the unit and full contact with the setting bed, unit, and prepared surface are required. Full coverage is required to provide sufficient adhesion of the finish material to the base coat. Without appropriate adhesion, it is possible the veneer units would not have sufficient shear or tensile bond strength to resist applied stresses, putting them at risk of detaching from the substrate. Additionally, voids in the setting bed (Fig. 10) can collect water that penetrates the finish coat. Water that remains in these void pockets is subject to freezing and thawing effects that can impart expansive forces on the back side of the adhered veneer and spall it from the wall surface. CONCLUSION In summary, MSV can be an economical, attractive, and durable cladding material when properly designed, detailed, and applied. With roots in portland cement plaster, MSV shares many of the same design and application techniques. As a result, the MSV base coat is often governed and specified by stucco standards ASTM C926 and ASTM C1063. In addition to stucco, MSV also shares common elements with masonry cladding. Masonry codes/specifications (for example, TMS 402 and ASTM C270) and masonry industry standards (for example, BIA Technical Note 28C, NCMA TEK 6-3c). Proper knowledge and understanding of these requirements and industry standards is key to a proper and successful installation. Common pitfalls in the design and installation of MSV include improper integration of WRB materials, insufficient lath embedment, improper accommodation for differential movement, and insufficient coverage on the back side of face units. Awareness of these common mistakes can avoid problems in MSV systems and costly repairs. II ii B E C International Convention & Trade Show | September 15-20, 2021 A Aguirre and Innocenzi | 229 Figure 10. Incomplete setting bed resulted in voids/pockets behind the adhered brick veneer. Figure 8. Large area of manufactured stone veneer without any control joints. Figure 9. Close-up view of Fig. 8 showing cracked manufactured stone veneer (MSV) likely resulting from the absence of control joints in a large surface area of MSV. REFERENCES 1. International Conference of Building Officials (ICBO), Uniform Building Code. Pasadena, CA: ICBO, 1967. 2. Masonry Veneer Manufacturers Association (MVMA), Installation Guidelines for Adhered Concrete Masonry Veneer. Washington, DC: MVMA, 2009. 3. International Code Council (ICC), 2018 International Building Code. Country Club Hills, IL: ICC, 2017. 4. ICC, 2018 International Residential Code. Country Club Hills, IL: ICC, 2017. 5. The Masonry Society (TMS), Building Code Requirements for Masonry Structures, TMS 402-16. Boulder, CO: TMS, 2016. 6. TMS, Specification for Masonry Structures, TMS 602-16. Boulder, CO: TMS, 2016. 7. ACI (American Concrete Institute) Committee 524, Guide to Portland Cement-Based Plaster (Farmington Hills, MI: ACI, 2008). 8. ASTM Subcommittee C11.03, Standard Specification for Application of Portland Cement-Based Plaster, ASTM C926-20b. West Conshohocken, PA: ASTM International, 2020. 9. ASTM Subcommittee C11.03, Standard Specification for Installation of Lathing and Furring to Receive Interior and Exterior Portland Cement-Based Plaster, ASTM C1063-20. West Conshohocken, PA: ASTM International, 2020. 10. ASTM Subcommittee C15.05, Standard Practice for Installation Methods for Cement-Based Adhered Masonry Veneer, ASTM C1780-20. West Conshohocken, PA: ASTM International, 2020. 11. Masonry Veneer Manufacturers Association/National Concrete Masonry Association (NCMA), Installation Guide and Detailing Options for Compliance with ASTM C1780, 5th ed., 4th printing. Herndon, VA: NCMA, 2020. 12. Masonry Veneer Manufacturers Association/NCMA, Installation Guide and Detailing Options for Compliance with ASTM C1780, 5th ed., 1st printing. Herndon, VA: NCMA, 2017. 13. Herb Nordmeyer, “Are Control Joints Needed with Adhered Concrete Masonry Veneer?” accessed September 29, 2020, https://www.multibriefs.com/briefs/ncmaorg/AreControlJointsNeededFINAL-%20ENewsSolutionCenterJun19.pdf, 2011. 14. Brick Industry Association (BIA), “Thin Brick Veneer,” BIA Technical Note 28C. Reston, VA: BIA, 2014. 15. Indiana Limestone Co., Thin Veneer Installation Guide. Bloomington, IN: Indiana Limestone Co., 2016. 16. Rocky Mountain Masonry Institute (RMMI), Adhered Natural Stone Veneer Installation Guide, updated ed. Denver, CO: RMMI, 2010. 17. NCMA, “Concrete Masonry Veneers,” NCMA TEK 3-6C. Herndon, VA: NCMA, 2012. 18. NCMA, “Crack Control for Concrete Brick and Other Concrete Masonry Veneers,” NCMA TEK 10-4. Herndon, VA: NCMA, 2001. 230 | Aguirre and Innocenzi IIiiBEC International Convention & Trade Show | September 15-20, 2021
