Adhered masonry veneers: Converging the crafts of brick and tile

Preface: This article is adapted from an original paper authored by Scott Conwell, FAIA, FCSI, LEED AP and Sunup Mathew published by The Masonry Society (TMS) in the Proceedings of the 14th North American Masonry Conference (14NAMC), June 2023.

Abstract

Many commercial and residential projects attempting to maintain the look of masonry while achieving perceived cost savings use thin adhered brick, stone, or manufactured stone units over a masonry or non-masonry backing. Adhered veneer can be a viable alternative to anchored veneer in certain applications, but only when designed and installed correctly. As the use of adhered masonry systems becomes more widespread, preventable failures are also becoming frequent.?

This paper examines specific design and construction techniques common to anchored veneer that may be adapted to adhered systems. It identifies methodologies commonly used in anchored veneer that translate well to adhered systems, as well as concepts that pose challenges to adhered systems like drainage accommodations for bulk water, flashing, air barriers, and wall insulation.?

The paper also analyzes design and installation techniques that have proven successful for tile setting but are relatively new or uncommon in the field of traditional masonry, particularly with respect to types of trowels and other tools, types of mortar, various mortar application techniques, embedment of the units, and methods of pointing and grouting.??

The tile setting trade, closely allied to the bricklaying trade, has well-established standards, design practices, and construction techniques that have resulted in successful installations for decades. Due to their similarity, the masonry industry would do well to adopt many of the design and installation methods used for tile, bringing a parity to these systems and a unified set of information for both designers and installers.

1. Introduction

Adhered masonry veneer (AMV) is a wall system comprising direct-bonded masonry units supported by the backing through adhesion to a structural backing such as masonry or concrete; or to either a scratch coat and lath or a cement backer unit that is fastened to a structural backing such as masonry, concrete or stud walls. AMV gained popularity in California as a viable alternate to anchored masonry veneer in the 1960’s. The high seismicity and warm-dry climate in CA made it an ideal candidate for adhered masonry veneer applications. The reduced weight and negligible differential movement in a seismic event allowed for easier design and detailing while the low-moderate moisture load due to wind driven rain or vapor drive allowed for a barrier-type wall design without a cavity behind the veneer. Historically, AMV systems have performed fairly well in California for these reasons.

AMV has gained popularity across United States in the last 2 decades because of perceived cost savings and reduction in the wall section and dead load. As the use of thin veneer units have increased, the system evolved from a simple application to systems that address moisture drainage, ventilation and energy efficiency. The design and installation of AMV shall meet the requirements of Chapter 13 in TMS 402-22 Building Code Requirements for Masonry Structures (TMS 402) and Chapter 14 of the International Building Code (IBC) 2021 (IBC 2021). Also, careful attention is needed to address the moisture and vapor movement.

When designed per the prescriptive requirements of TMS 402, AMV units shall not exceed 2 5/8 in. (66.7 mm) in specified thickness, 5 sq. ft. (0.46 m2) in total face area, or 30 psf (146.5 kg/m2) in weight. Within these dimensional and weight constraints, AMV can comprise a variety of adhered units including thin brick (clay), natural stone, manufactured stone (cement-based), or calcium silicate. For the purposes of this paper, units classified as “tile” in the American National Standard Specifications for Ceramic Tile (ANSI A137.1) are outside the scope of AMV, since adhered tile has well established installation standards and work practices. Therefore, the materials of ceramic tile, glazed wall tile, quarry tile, and porcelain tile are excluded from the scope of this paper. This paper will focus exclusively on exterior applications of thin brick, natural stone, manufactured stone, and calcium silicate meeting the dimensional and weight criteria.

AMV is a unique system. In many ways, its design and installation are similar to those of traditional anchored veneer masonry, but in other ways, AMV is more similar to the design and installation of ceramic tile. The crafts of bricklaying and tile setting, both trowel trades, fall under the umbrella of the International Union of Bricklayers and Allied Craftworkers. Nevertheless, they remain two discreet trades, each with a unique set of skills, tools, techniques, training, and vocabulary.

2. Installation methods, general

Adhered veneer installation methods can be separated into two categories: thick-set and thin-set installation methods. There are many variations of configurations within each of these classifications. Note that in both thick-set and thin-set AMV walls, the bonding mortars specified are the same mortars traditionally used for ceramic tile installations conforming with American National Standards Institute (ANSI) A108.4 or ANSI A108.15. Therefore, any installer of adhered masonry should be trained and adept at working with the tools and techniques required of these materials.

2.1. Thick-set method

A thick-set method uses a thin or medium mortar bond coat applied to a brown coat, or a cement plaster scratch coat with lath fastened to the backing. Brown coats are incorporated over the scratch coat to correct and plumb substrates that vary from a planar surface by greater than +/- 1/4" inch in 10 feet (6 mm in 3.05 m). An example of a commercial exterior thick-set wall is as follows (Also see Fig. 1):

Backing: Steel studs spaced max. 16 in. (406 mm) on center

Sheathing: Glass mat reinforced gypsum board

Water Resistive Barrier (WRB): 2 layers building wrap, or 1 layer plus drainage material

Scratch coat: Type N or Type S masonry mortar, 1/2 in. (13 mm) nominal thickness

Lath: Approved lath embedded in scratch coat, attached to sheathing with approved fasteners

Bond coat: ANSI A118.4 or ANSI A118.15 bonding mortar

Veneer: Thin brick, natural stone, manufactured stone, or calcium silicate

In the example above, as an alternative material for the bond coat, it was permissible to use ASTM C270 Type S masonry mortar for exterior walls less than ten feet high according to MVMA and 2016 TMS 402. Beginning with the 2022 TMS 402 code, this wall requires one of the ANSI A118 mortars specified as the bond coat.

2.2. Thin-set method

A thin-set method uses a thin or medium mortar bond coat applied to a cement backer unit, concrete, or masonry substrate. An example of a commercial exterior thin-set wall is as follows (Also see Fig. 2):

Backing: Steel studs spaced max. 16 in. (406 mm) on center

Sheathing: Cement board

WRB: 2 layers building wrap, or 1 layer plus drainage material

Bond coat: ANSI A118.4 or ANSI A118.15 bonding mortar

Veneer: Thin brick, natural stone, manufactured stone, or calcium silicate

3. Substrates

According to ANSI A108.01, suitable backings for exterior tile walls laid with modified cement mortars include masonry, concrete, and cementitious backer units. This standard also states that the quality and cost of ceramic installations are influenced by the stability, permanence, and precision of installation of the backing material. These criteria are equally applicable to substrates for adhered veneer masonry.

Substrates for AMV affect the finish in the same way as a tile assembly, therefore installers of AMV should pay close attention to the quality of the substrate. Substrates must be structurally sound, clean, dry, and free of oily or waxy films and all foreign matter. All substrates also have flatness and deflection requirements. Traditional bricklayers may not be in the habit of assessing a wall’s substrate for its suitability to receive adhered veneer, but this is an important part of an installer’s job.

In addition to general requirements for all substrates, there may be specific requirements for different materials.

Concrete and masonry

According to ANSI A108.01, when adhering directly to concrete or masonry, these materials should be free of contaminants such as sealers, cleaning compound, coatings, oil, and dust. Form release agents are also to be avoided, as they may inhibit bond. Surface preparation may be necessary to provide a bondable surface. Alternatively, a thick-set mortar bed application may be used over the concrete or masonry.

Thick-set mortar bed application

A scratch coat of cement mortar with embedded lath reinforcement, and optional leveling coat, a.k.a. brown coat, can be applied over a backing of concrete, masonry, or sheathing, creating a substrate for the AMV. According to ASTM C1780, the scratch coat should be applied minimum 1/2 in. (13 mm) thick, with sufficient material and pressure to fully engage and encapsulate the lath, and with sufficient thickness to allow for scoring the surface. The entire surface should be scored in the horizontal direction only. Scratch coat shall cure for 48 hours prior to unit installation to provide a firm surface to install the units to.

When the scratch coat is applied over concrete, ANSI A108.01 specifies that the concrete be bush hammered or heavily sandblasted to provide a degree of roughness to optimize mechanical bond. A leveling coat is required when a mortar bed thickness of more than 3/4 in. (19 mm) is required to build out the substrate. The scratch coat must be cured for at least 24 hours before applying the leveling coat.

Cement board

ASTM C1780 contains specific requirements for cement backer board used as a substrate for adhered masonry veneer. Cement board, a.k.a. cementitious backer units (CBU), shall be in conformance with ASTM C1325 6. Other types of backer boards including fiber-cement backer board (ASTM C1288), coated glass mat water-resistant gypsum backing panel (ASTM C1178), glass mat gypsum panel (ASTM C1658), and others are not acceptable backing for exterior adhered masonry. Exterior cement boards shall be installed over approved sheathing and WRB. When cement board is used, a single layer of WRB is permitted.

Joint treatment for exterior CBU shall be treated with modified mortars meeting requirements of ANSI A118.4 or A118.15, and 4-in. (102 mm) wide alkali resistant fiberglass mesh tape. Tile installers often perform the joint treatment after carpenters have installed the CBU, but many traditional bricklayers are not accustomed to taping and treating joints in cement board. All AMV installers should be well versed at treating joints between cement boards.

3.1. Deflection requirements

As with tile installation, deflection is of paramount concern for AVM walls. Cement board on studs required a stud spacing of 16” (406 mm) on center, maximum, and when steel studs are used, they must be at least 3 1/2” (89 mm) studs, 20-gauge minimum thickness. If the backing wall is not sufficiently stiff, joints in the AVM may crack and the units may become debonded when exposed to severe lateral loads. It is not the responsibility of the AVM installers to design for deflection, but they should be aware of the requirement, and if they have any doubts that the backing is stiff enough, they should raise concerns to the general contractor or owner.

TMS 402 limits the out-of-plane deflection of the backing that supports AMV to hb/360 under application of 0.42 times the strength level wind load, and hb/150 under application of the strength level seismic load. It states, “The limitation is both to limit veneer cracking and to provide out-of-plane stability under the eccentric load from the adhered veneer.” Since the weight of the veneer is transferred to the backing through adhesion, it is fair to assume that cracking of the adhered veneer is more critical than the stability. Note that the requirements set forth in TMS 402-22 are consistent with 2021 IBC requirements for exterior walls with plaster or stucco finishes.

3.2. Flatness requirements

According to ANSI A108.01, wall surfaces to receive ceramic tile should be plumb and true with variations not exceeding 1/4 in. in ten ft. (6 mm in 3 m) from the required plane. Substrates not meeting this requirement should be remediated with a compatible patching material filling in the low areas before tile or thin masonry units can be adhered. Flatness requirements for radial walls and other walls that are non-planar by design are outside the scope of this paper.

Installers should not use bonding mortar to bring the wall to a flat plane. Both ANSI A118.4 and ANSI A118.15 explicitly say that these materials are not intended to be used in truing or leveling underlying substrates.

In the context of ceramic tile installations, lippage in the finished tile work is a function of substrate flatness and other factors, so it should also be addressed here. Because ceramic tile is manufactured to different standards and tolerances than thin brick, natural stone, manufactured stone, and calcium silicate units, tile work is held to tighter lippage tolerances. There are currently no lippage tolerances for adhered masonry veneer.

4. Moisture mitigation

IBC 2021 requires the design of exterior walls to prevent the accumulation and condensation of water within the assembly and to provide a means to drain the water that enters the assembly. Further, the TMS 402/602-22 Building Code Requirements and Specifications for Masonry Structures (TMS 402/602) requires that all veneers, including adhered veneers, be designed and detailed to resist water penetration. Additionally, tile installation standard ANSI A108.01 requires exterior wall design to prevent moisture from collecting behind the tile work. These can be achieved with the use of flashing, weep devices, drainage media, and waterproofing.

4.1. Flashing and weep devices

Flashing in adhered veneers must be corrosion resistant and integrated with the WRB when present. Flashing should be included at all wall terminations and penetrations. Weep screeds should also be corrosion resistant, should terminate behind the WRB if present, and should allow water to exit the wall assembly.

Since flashing and weep devices are part of the veneer system, installation of these components typically fall within the scope of the mason contractor or tile contractor. Installers of AMV should have a basic understanding of moisture management and the skills to install these accessories.

4.2. Drainage media

With the increasing use of polymer modified bonding mortar and exterior rigid insulation, it is more important than ever to drain the wall and aid drying of the mortar bed in both directions. Designers are advised to specify a drainage medium, preferably one that allows for moisture and air movement in both directions to the exterior of the continuous rigid insulation (if installed) or moisture barrier, and vent the cavity using flashing and weep holes.

Whereas anchored veneer masonry is typically designed with a drainage cavity and other accommodations to collect and divert water that penetrates the cladding, drainage of bulk water poses a unique challenge for AMV walls. Unlike anchored veneers, walls consisting of thin cladding adhered to a backing do not lend themselves to providing a convenient drainage path. Exterior adhered tile walls have traditionally been designed as barrier walls, with the tile and the waterproofing membrane behind it acting as barrier to moisture infiltration. AMV walls may be designed as barrier walls similar to tile walls, but preferably they should incorporate the use of a drainage medium behind the thin veneer and function as a drainage wall. ASTM C1780 describes applications over a designed drainage space as a special application, specifying a minimum drainage gap of 3/16 in. (5 mm) and maximum drainage gap of 3/4 in (19 mm). Rather than being considered special, drainage walls should become the norm for adhered veneer walls.

Recognizing the benefits of drainage walls, the masonry industry is rapidly endorsing details that show drainage media for AMV systems. Reference details by International Masonry Institute and MVMA show drainage media behind the adhered veneer as a mechanism for keeping the wall dry. With the movement toward AMV drainage walls, all installers of adhered masonry should be adept at working with flashing, weep devices, and drainage media.

4.3 Waterproofing membrane / WRB

According to ASTM C1780, the water resistive barrier (WRB) is the material behind an exterior wall covering that is intended to resist liquid water that has penetrated the exterior covering from further intruding into the exterior wall assembly. Some AMV systems use a liquid applied WRB as part of a proprietary system, referring to liquid or sheet membranes provided by the same manufacturer as the bonding mortar. The ceramic tile industry refers to this WRB material as “waterproof membrane.”

Waterproof membranes for exterior adhered tile assemblies are specified to prevent moisture intrusion and protect adjacent building materials; these membranes should meet the requirements of ANSI A118.10. The TCNA Handbook’s Membrane Selection Guide describes these membranes as single- or multi-component membranes applied in liquid/paste form, which cure into continuous membranes, or membranes applied in flexible sheet form. Some of these membranes have integral reinforcing fabrics for tensile or strength and minor crack-bridging properties. Others are designed to be used as a combination waterproofing and setting material for the tile.

Depending upon the type of waterproofing membrane, manufacturers may require that the tile products be installed on a reinforced portland cement setting bed applied over the membrane (thick-set method), directly on the membrane with an ANSI A118.4 or A118.15 mortar, or bonded to the membrane using a troweled application of the waterproofing membrane product.

ASTM C1780 describes WRB thusly: Install two separate layers of WRB outboard of the sheathing material in accordance with the WRB manufacturers’ installation instructions. The WRB shall be integrated with all flashing materials in such a manner that prevents penetration of water beyond the WRB. Some building code jurisdictions allow a single layer WRB when a drainage wall system is used. When the WRB is installed inboard of cement board, a single layer of WRB is permitted since there is not a need for a sacrificial layer of WRB.

Whether the membrane is fabric-reinforced liquid, single component liquid, or sheet goods, AMV installers should be trained and adept at working with all types of waterproof membranes, following manufacturers’ recommendations in all cases.

5. Bonding mortar

TMS 402/602 makes reference to “setting bed mortar,” and ASTM C1780 defines “setting bed” as the mortar used to bond units to a prepared surface or scratch coat. The ANSI A108 standards and the TCNA Handbook identifies this same material as the “bond coat” or “bonding mortar.” These terms may be used interchangeably. As noted earlier, bonding mortar for all types of exterior adhered masonry veneer walls must conform to ANSI A118.4 or ANSI A118.15.

5.1 Bonding mortar: materials

ANSI A118.4 describes “modified dry-set cement mortar” as a mortar for the bonding of ceramic tile to which additives have been incorporated to improve performance above a non-modified dry-set mortar. ANSI A118.15 describes “improved modified dry-set cement mortar” as a mortar for the bonding of ceramic tile to which additives have been incorporated to improve performance, and specifically designed to obtain shear bond strengths greater than those required of modified mortars. While these mortars may have been initially formulated for the installation of ceramic tile, their application has expanded to include the installation of other types of adhered units.

According to both standards, these bonding mortars should be applied between the substrate and the plane of the back of the veneer unit to a thickness of 3/32 in. (2.4 mm) (nominal) to 1/4 in. (6.4 mm) (nominal) after the tile is embedded.

Bonding mortars manufactured to these standards may be further formulated to achieve special properties including thicker applications for large and heavy tile, fast-setting properties, extended open time properties, and sag resistant properties to reduce slippage on vertical installations.

5.2. Bonding mortar: mixing and application

ANSI A108.5 is the installation standard for modified and improved modified cement mortars. This standard requires 95% coverage and embedment for exterior installations. The standard describes procedures for mixing and applying ANSI A108.4 and A108.15 mortars and the application of the mortar to the backing or substrate as follows:

• Add dry mortar mix to amount of latex or water specified by manufacturer and mix thoroughly to obtain complete and visually uniform wetting of the dry mortar mix. Slake for 15 minutes and remix before using.
• The proper mortar consistency is such that when applied with the recommended notched trowel to the backing, the ridges formed in the mortar will not flow or slump.
• Apply mortar with flat side of trowel over an area no greater than can be covered with tile before the mortar skins over. Using a notched trowel of type recommended by mortar manufacturer, comb mortar to obtain even setting bed without scraping backing material. Cover surface uniformly with no bare spots and with sufficient mortar to ensure minimum mortar thickness of 3/32 in. (2 mm) between tile and backing after tile has been beaten into place. Tile shall not be applied to skinned-over mortar. (Author’s note: “adhered masonry unit” may be interchanged with the term “tile.”)

In some cases, mortar may also be applied to the back of the veneer units. This is known as back buttering. ASTM C1780 describes “back butter” as the act of applying bonding mortar to the back of a masonry unit. ANSI A108.5 describes the process as follows:

• If 95% mortar coverage is specified in the project specifications, back butter each tile with bond coat, or select a notched trowel sized to facilitate the proper coverage, key the mortar into the substrate with the flat side of the trowel, and comb with the notched side of the trowel in one direction.

These referenced standards provide good foundational information, but AMV installers should always follow instructions and recommendations of the mortar manufacturer. All AMV installers, whether bricklayers or tile installers, should be familiar and skilled in these methods of mixing and applying mortar.

6. Placing the units

After the mortar is applied to the substrate and/or the back of the units per recommendations of the mortar manufacturer, the units must be adequately embedded. ANSI A108.5 requires 95% minimum mortar coverage, including embedment, for exterior applications. Embedment is achieved as the units are applied.

ANSI A108.5 addresses techniques for placing the adhered units; note that “adhered masonry unit” may be interchanged with the term “tile” in the excerpt below.

• Press tile into freshly combed mortar, ensuring mortar contact with tile. Maintain joint alignment and spacing. Keep an adequate joint depth open for grouting.
• For exterior applications, average contact area shall be not less than 95% when not less than three tiles are removed for inspection. The 95% coverage shall be sufficiently distributed to give full support of the tile.
• Embed the tile in the mortar by beating-in, pushing in a direction perpendicular to the combed ridges, or other means to achieve specified coverage. The method used should produce maximum coverage with the corners and edges fully supported. Periodically remove and check a tile to assure that proper coverage is being attained.

ASTM C1780 also provides instructions on setting the units:

• Set the units in a full setting bed mortar. Mortar between the unit and the prepared backing surface shall be a minimum thickness of 1/2 in. (13 mm).
• The total thickness to include setting bed mortar and scratch coat shall not exceed 1 1/4 in. (32 mm).
• [Provide] setting bed with complete coverage of the back of the unit and full contact between the mortar setting bed, unit, and prepared backing surface.
• Method A – Back butter the unit using sufficient mortar and pressure to fill texture and voids in back of unit. While setting bed mortar is wet, press and work the unit onto the backing with enough pressure to force mortar to squeeze out around the entire perimeter of the unit.
• Method B – The mortar setting bed shall be installed by trowel application 1/2 - 3/4 in. (13-19 mm) thick directly to the prepared backing surface. Back butter the unit, sufficient mortar and pressure to fill texture and voids in back of unit. While setting bed on the prepared backing surface is plastic, press and work the unit into the setting bed with enough pressure to force mortar to squeeze out around the entire perimeter of the unit. Limit mortar setting be open time and work only an area that can be covered before mortar skins over.

Some of the specific techniques like whether mortar must be applied to the backing, the thickness of the bond coat, and the recommended percentage mortar of coverage are inconsistent between ANSI A108.5 and ASTM C1780. The installer should always follow the instructions of the mortar manufacturer. All AMV installers, whether bricklayers or tile installers, should be trained and skilled in this method of placing the units to at least 95% coverage and embedment.

7. Finishing

Once the bonding mortar has sufficiently cured (around 24 hr. after the installation), joints between the units in AMV walls are typically grouted in with a pointing mortar. The pointing mortar is typically ASTM C270 Type N or Type S mortar, applied from a hawk or a grout bag, and tooled to the joint profile specified. Since workability and ease of cleaning are more critical over the strength of the pointing mortar, Type N may be preferred over Type S mortar. Additionally, installing from a hawk is preferred in severe weather conditions since the grout bag application requires more plastic mortar that is generally achieved with additional water, which can result in a less durable installation.

Place the pointing mortar on to the mortar hawk and begin with horizontal joints. Hold the hawk against the wall and just under the joint to be filled, push mortar into the joint with a tuckpointing tool and pack the joint with mortar. Scrape off any extra mortar so the mortar in the joint is flush with the units without excessive mortar smear on the face of the AMV units. Subsequently install the vertical joints by placing a small amount of mortar onto the pointing tool and packing the mortar into the joint. Scrape off any extra mortar so the joint is flush with the units. Tool the joints to the desired profile when the mortar is thumbprint hard.

The common practice in tile installation of smearing grout on the face of tile should be avoided for AMV since the surface characteristics of the units would make it extremely hard to clean mortar smears. Use a dry, soft-bristled, non-metallic brush to clean off remaining mortar from the surface of AMV units.

Joint finishing with masonry mortar is a work practice typically performed by bricklayers and tuckpointers, and it may be a new skill for tile installers. Since joint finishing is a critical part of AMV walls, all installers of adhered masonry should be adept at grouting and tooling the joints with masonry mortar.

8. Movement joints

8.1 Design for movement in AMV

AMV systems should be designed to accommodate stresses due to changes in temperature and moisture. While different materials move differently, the overall movement of the system is dependent on the substrate movement. Hence the adhered masonry units should be designed according to the design of movement joints in the substrate. In instances where the substrate is different from the structural backing (in cases where plaster or cement board is installed over rigid insulation on CMU or concrete), follow guidelines for substrate to locate the movement joints. Movement joints should be installed at specified spacing in the field of the wall, near the corners, at changes of height, at dissimilar backing materials, and at openings. Just as in anchored veneer and tile, it is the responsibility of the design professional to locate the movement joints in adhered masonry veneer.

8.2. Movement joints on thick-set applications

ASTM C1063 specifies requirements for movement joints in thick-set walls. One can follow the guidelines for plaster and lath.

Movement joints shall be installed in walls to delineate areas not more than 144 ft2 (13.4 m2) and the distance between control joints shall not exceed 18 ft. (5.5 m) in either direction or a length-to-width ratio of 2 1/2 to 1. Movement joints shall be installed in change of heights, dissimilar materials for back up and at openings.

Casing beads shall be installed back to back at the movement joints with backer rod and sealant between them. Casing beads help to achieve a clean edge at the control joints and termination to install sealant and help control the thickness of the mortar bed. The separation spacing shall be not less than 1?8 in. (3.2 mm) or as required by the anticipated thermal exposure range.

To control the cracking due to stress concentrations at the corners use a corner lath [typical corners laths have 3 in. (76 mm) legs at inside and outside corners] and lap 1 in. (25 mm) minimum with the field lath.

8.3. Movement joints on cement board substrates

Movement joint recommendation for AMV cement boards vary from manufacturer to manufacturer. These recommendations range from 12-16 ft. o.c. (3,660 – 4,880 mm) for movement joint spacing. Note that the Tile Council of North America (TCNA) has the very conservative guidelines of 8-12 feet (2,440 – 3,660 mm) spacing for movement joints in ceramic tile assemblies, clarifying that it is the responsibility of the design professional to locate and dimension all movement joints. Movement joints should be continuous through the AMV unit and the cement board. To eliminate cracking at corners, the joints between cement boards must be treated with 4 in. wide alkali-resistant reinforced tape embedded in polymer modified bonding mortar conforming to either ANSI A118.4 or ANSI A118.15.

8.4. Requirements for CMU and concrete walls

When installing AMV to CMU or concrete backing, locate the movement joints on AMV at the same locations as the backing wall. When AMV is installed over plaster or cement board over CMU or concrete, follow the guidelines as described for those substrates, which may be spaced closer together than the control joints in the CMU or backing wall. The movement joints in the veneer that do not coincide with those in the backing wall need to extend only through the thickness of the substrate.

9. Conclusion

Adhered masonry veneer and tile installation are different enough that they will always remain two separate trades, and the growth of adhered masonry veneer will not result in the blending together of those trades. However, because the skills, tools, and techniques required of AMV draw from both trades, it becomes important to define a single set of best practices that both trades can work from. If bricklayers use only traditional masons’ tools and techniques for AMV, it would be incorrect; and if tile setters used only tile tools and techniques for AMV, it would be equally incorrect. The masonry industry must not only define a single set of best practices for AMV, but we must train and equip both trades, bricklayers and tile installers, for adhered masonry veneer installation based on those best practices.

10. References

ANSI 108.01 American National Standard Specifications for the Installation of Ceramic Tile - General Requirements: Subsurfaces and Preparation by Other Trades, 2021.

ANSI A108.02 American National Standard Specifications for the Installation of Ceramic Tile - General Requirements: Materials, Environmental, and Workmanship, 2021.

ANSI A118.4 American National Standard Specifications for Modified Dry-Set Cement Mortar, 2021.

ANSI A108.5 American National Standard Specifications for the Installation of Ceramic Tile - Installation of Ceramic Tile with Dry-Set Portland Cement Mortar for Latex-Portland Cement Mortar, 2021.

ANSI A118.10 American National Standard Specifications for Load Bearing, Bonded, Waterproof Membranes for Thin-Set Ceramic Tile and Dimension Stone Installation, 2021.

ANSI A118.15 American National Standard Specifications for Improved Modified Dry-Set Cement Mortar, 2021.

ANSI A137.1 American National Standard Specifications For Ceramic Tile, 2022.

ASTM C1063-22 Standard Specification for Installation of Lathing and Furring to Receive Interior Portland Cement-Based Plaster, 2022.

ASTM C1325-22 Standard Specification for Fiber-Mat Reinforced Cementitious Backer Units, 2022.

ASTM C1780-20 Standard Practice for Installation Methods for Cement-based Adhered Masonry Veneer, 2020.

Handbook for Ceramic, Glass, and Stone Tile Installation (2022), Tile Council of North America (TCNA).

International Building Code 2021 (IBC 2021).

Lstiburek, Joseph W. (2019), Stoned: Problems with Thin Stone and Thin Manufactured Stone Veneer, AKA, “Lick and Stick Stone” AKA “Lumpy Stucco”, ASHRAE Journal Vol. 61, Issue 10.

Masonry Veneer Manufacturers Association, Installation Guide and Detailing Options for Compliance with ASTM C1780 For Adhered Manufactured Stone Veneer 5th Edition, 5th Printing, October 2021.

TMS 402/602-22 Building Code Requirements and Specifications for Masonry Structures, 2022.