by brittney_cutler | December 29, 2021 10:40 am
By Bill Egan and Dean Seabrook
Exterior insulation and finish systems (EIFS) are above-grade, exterior wall claddings used across the country on residential and commercial buildings. It is a popular cladding choice due to benefits such as high thermal efficiency, cost effectiveness, and design versatility. EIFS is used in new construction as well as to retrofit existing buildings, and can be installed either panelized or as an in-place application. The systems are used on all types of buildings including hospitality, retail, amusement, single- and multi-family homes, condominiums, apartments, and casinos.
EIFS components include a thermal insulation board, an adhesive attaching the thermal insulation board to the water-resistive barrier (WRB) system, a glass fiber reinforcing mesh embedded in a basecoat on the face of the thermal insulation board, and a finish coat. Since EIFS are proprietary systems, the manufacturers determine the material and technology for each component, installation methods, and conduct testing to demonstrate performance and code compliance. Initially, material choices for each of the EIFS components were limited, but industry growth and demand have resulted in many new options across key system elements. Some of the innovations have occurred in new finish appearances. While originally limited to integrally colored and textured finishes, many options such as thin masonry veneers are now available, greatly expanding design flexibility for architects and designers.
Drivers for new finish options
EIFS is a versatile building material and exterior wall cladding system. While a primary function of the system’s continuous insulation (ci) board is thermal properties, it can also be cut into special shapes, enabling the creation of a range of architectural features. Some commonly used shapes include cornices, quoins, window and door trims, moldings, medallions, caps, graphics, and arches. Further design options and appearances can be achieved by forming aesthetic grooves in the insulation board to provide the look of panels, cut stone, etc. These options give architects and designers the opportunity to create a variety of appearances as well as themes aligning with a building’s use, location, or function.
Over time, architects, designers, owners, and other construction professionals sought alternatives to the original EIFS finish options. Design trends, such as the use of ci, and buildings with multiple claddings, further influenced the demand for additional options.
Continuous insulation is available in a range of thicknesses, enabling EIFS to meet the project’s thermal protection goals. As an EIFS component, ci is integral to the system’s installation and performance. The system allows for ci thicknesses of at least 125 mm (5 in.) and is easily integrated into the overall building enclosure. While integral to EIFS, ci is an optional or added wall assembly component for many other types of veneers and claddings, which can result in additional design, installation, and performance considerations. For example, special detailing will often be needed for wall cladding closure pieces and integration with other enclosure components such as windows and doors since the wall thickness increases, which moves the exterior wall plane perpendicularly outward. With mechanically fastened cladding systems, additional support or attachment mechanisms may be necessary since the nonstructural ci does not support the cantilevered cladding weight. Depending on the type of ci and building, additional fire tests may also be necessary. As demands for ci have increased, so has the need for new EIFS finish options replicating the appearance of other cladding materials.
To achieve the desired architectural appearance, many buildings are constructed with multiple claddings such as EIFS combined with other veneers including stone, brick, metal, or ceramic tile. Structures with multiple claddings require additional considerations in terms of installation as well as design and material compatibility. For example, there may be more than one subcontractor installing the claddings, thus resulting in the need for careful scheduling and co-ordination by the contractor of record. With respect to design, contract documents should include details to assure continuity and compatibility if there are different types of ci and WRBs. Details are also needed to transition between the different claddings for weather-tightness, appearance, and compatibility with the overall building enclosure.
Over the years, EIFS manufacturers have introduced many new finishing materials as well as application techniques to provide additional performance and appearance possibilities. These have been relatively thin materials applied by trowel or spray in a manner similar to traditional EIFS finish coat technology. ‘New look’ or specialty finish appearance options now include:
• textures such as ultra-smooth, fine, and coarse;
• old-world effects;
• metallic; and
Finishing materials are also available with enhanced performance properties such as superior fade resistance, increased hydrophobic abilities, high elongation, and improved resistance to dirt pickup.
New masonry veneer finish options
Recently, some manufacturers have started to offer systems incorporating thin veneers such as ceramic tile, masonry, natural stone, and brick as an alternative to the original EIFS finish coat. While using typical EIFS components, these systems are sometimes referred to as insulated masonry veneer systems. Key features of such applications include:
• retain ci in conjunction with the option of thin veneer materials;
• realize depth, 3D characteristics, and natural veneer appearance;
• provide additional finish options;
• maintain continuity of the WRB and drainage plane; and
• provide a fully engineered and tested cladding system throughout the building façade.
When a thin veneer finish is incorporated into an EIFS, the following are important considerations:
• shear bond strength of the composite veneer, setting mortar, and reinforced basecoat when subjected to vertical shear tests;
• tensile bond strength between all components when subject to normal loading;
• freeze/thaw resistance of the composite veneer, setting bed mortar, reinforced basecoat, and insulation board;
• rigidity and support provided by the backup assembly;
• creep/deflection and shear properties of full-size wall assembly panels subject to vertical loads;
• seismic/racking performance of the veneer system when subjected to a static lateral load parallel to the wall plane;
• transverse load tests for wind load capacity of the wall assembly; and
• fire performance related to endurance and flame propagation.
Thin veneer finish application
Most aspects of an EIFS application and components including the WRB, ci board, basecoat, and reinforcing mesh are similar regardless of whether the finish is a thin veneer or a traditional, textured finish coat. Systems with thin veneers may incorporate a heavier reinforcing mesh and thicker basecoat for increased strength and rigidity. Although recommended ci thicknesses may be slightly less when thin veneers are used, the system is typically fastened to the substrate with the same basecoat adhesives used with EIFS and a textured finish. This well-known EIFS attachment method alleviates penetrations and thermal bridging associated with mechanical fasteners, and has decades of proven performance in a wide variety of climates. Tests related to basecoat adhesive performance include water impermeability and absorption, drainage, wind load, and tensile bond strength under wet as well as dry state conditions.
Commonly used thin veneers include natural or manufactured stone, ceramic tile, and brick. Products are selected primarily on appearance along with performance attributes. Veneers are generally limited in terms of weight, size, and thickness with common requirements being maximum weight of 74 kg/m2 (15 psf), 1-m (3-ft) single dimension/1/2 m2 (5 sf) total area and under 75 mm (3 in.) thick. Use and other limitations are typically a function of design considerations, local code requirements, and manufacturers’ substantiating data to support the application.
The finishing application consists of the veneer and setting bed mortar installed to the substrate. Setting bed mortars are typically dry, polymer-modified proprietary mix requiring water and mixing prior to application. The mortar mix adheres the veneer to dry, reinforced basecoat and other substrates such as poured or precast concrete, unit masonry, stucco scratch or brown coat, and cement board sheathing. Depending on the type of veneer, setting bed mortars are applied to the back of the veneer as a solid layer application or a notched trowel pattern. In some applications, a wet skim coat of setting bed mortar is applied to the substrate prior to the installation of the veneer. Application temperatures for the setting bed mortar are minimum 4 C (40 F), and the thickness of the setting bed mortar varies depending on the veneer type. Veneers and the wet setting bed mortar are pressed into place on the substrate in a manner that the mortar is free of voids (potential collection points for moisture).
While veneers can be installed as dry stack or open joint systems, most applications use grouting or pointing mortar to fill and provide weather resistance between the individual units. Various types of pointing mortars are available with selection typically a function of the veneer type, desired performance, manufacturer recommendations, or design considerations. The pointing mortar is struck or tooled prior to set to provide the desired appearance.
Whether the finishing option is a traditional, textured type or masonry veneer, the outermost surface maintains its primary function, which is to provide the desired appearance. Masonry veneer provides an additional aesthetic option while maintaining the many benefits of EIFS.
Bill Egan has more than 35 years of construction experience including product and system design, standards development, testing, building code compliance as well as claim investigation, resolution, and litigation. Prior to starting the Bill Egan Group, a provider of consulting services related to building enclosures and products, Egan held key technical roles with construction product companies manufacturing exterior insulation and finish systems (EIFS), stucco, air and water-resistive barriers, and architectural coatings. He can be reached at firstname.lastname@example.org.
Dean Seabrook is the territory sales manager for BASF Wall Systems in eastern Canada. He has been with the company for more than seven years and has over 25 years of experience in the construction industry. Seabrook is a board member of the EIFS Council of Canada (ECC) and a member of CSC’s Toronto Chapter. He can be reached at email@example.com.
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