Acoustical plaster helps create a comfortable interior environment for building occupants, thanks to its sound absorbing properties. Its design possibilities are flexible, since it can conform to an array of surfaces, from flat, to curved, vaulted, and in between. It’s also available in a wide array of finishes. Although white finishes are popular, color selection is unlimited, and additional textures, including the simulation of natural materials like stone, offer additional design options.
Sound Absorption
Acoustical plaster has microscopic pores that allow sound to travel through the plaster into an underlying acoustical board that’s part of the assembly and absorbs most of the sound. Large spaces with hard surfaces tend to reverberate sound, making intelligibility of voice, music, and other sounds challenging. Creating a pleasant acoustical experience has positive impacts on health, safety, learning, quality of life, and an occupant’s overall experience in a space. Acoustical plaster absorbs sounds, resulting in a reduction of the reverberation time, and allowing conversations or music, for example, to become clearer, even in the harshest of environments.
Systems
There are various acoustical plastering systems on the market with different mounting systems that may also impact the acoustical performance. Different mounting systems include direct to substrate, suspended, or direct to framing. There are also plaster only systems that can also be sprayed directly to the substrate without the use of an acoustical board.
Although moisture intrusion within building enclosures is one of the greatest risks to a building, acoustical performance is also high on the list. Highly trained, qualified craftworkers with artisan skills are necessary for the successful installation of acoustical plaster.
Applications
Acoustical plaster is commonly used in building types and spaces that need high performing sound absorptive characteristics. This includes spaces like museums, auditoriums, libraries, government buildings, religious institutions, healthcare facilities, and high-end residential or retail spaces.
Stucco assemblies draw on various materials, components, and practices, which can vary greatly throughout different regions of the U.S. Each system is designed to accommodate shrinkage, support the cladding system, and manage water with flashings. Stucco systems include:
Direct Applied
Stucco applied to mass walls like CMU and concrete is prevalent in the Southeast. This is considered a barrier wall strategy, as the intent is that there isn’t capacity for drainage. The performance of this assembly relies on water shedding completely at the outer face of the cladding. It may be appropriate, based on project specific conditions, to require additional detailing to mitigate risks. For example, direct application to a CMU wall may need additional detailing, like at rough openings, to manage the risks of fenestration leakage. It may also need water-resistive transition membranes at the CMU control joints that align with the stucco accessories in order to manage moisture in these localized areas where the stucco assembly or interface details are more susceptible to water leakage. In the case of direct applied stucco to cast in place concrete, adhesion testing and other quality assurance/control measures may be necessary to ensure adequate bond of the stucco assembly, due to density of the concrete and risk of not adequately removing form release agents.
Concealed Barrier Wall Strategy
Stucco with integral lath over framed walls with a building paper or wrap water-resistive barrier (WRB) is often found in the Southwest. This is considered a concealed barrier wall strategy, as the intent is that there’s little to no capacity for drainage. This may be an acceptable strategy based on geographic location, for example, where annual rainfall is low. Project specific conditions, like large overhangs that minimize moisture exposure, may also make it a suitable choice. The intent of the WRB is to protect the moisture sensitive back-up wall materials by placing them in the dry zone of the enclosure. Two layers of building paper, wrap, or other means may be required to provide a slight capillary and/or bond break with the stucco.
Drainage Strategy
Stucco with integral lath over framed walls and an water/air barrier and drainage mat is prevalent in the Pacific Northwest and also sometimes found in the Midwest and Northeast. This is considered a drainage strategy because of the integration of a space created by the drainage mat for drainage and drying. This strategy may be necessary or required by code depending on the geographic location, for example, in areas with moderate to high annual rainfall. Project specific conditions, like greater exposure to water due to building height, the amount and complexity of interface details, and other conditions that result in moderate to high moisture exposure, may also necessitate this strategy.
Contact IMI for guidance when evaluating an appropriate stucco assembly for your project.
Exterior Insulation and Finish System (EIFS) is an exterior wall cladding system that provides an insulated finished surface and waterproofing. EIFS can vary from project to project, but here are some typical components you may find in these assemblies.
Water and Air Barrier
The most common EIFS integrates a fluid applied water and air barrier membrane with accessories to aid in continuity. The membrane is often vapor permeable and allows the insulation board to be adhesively attached with vertical ribbons that create a space for drainage.
Adhesive
Often, EIFS integrates an adhesive to secure the typical rigid insulation boards. The adhesives are applied to create a space between the water-resistive barrier and the backside of the insulation board and oriented vertically to allow for drainage of water to egress the EIFS at integrated flashings. Both polymer-modified cement-based adhesives and polyurethane foam adhesives are available.
Insulation Board
Expanded polystyrene (EPS) is the most common insulation board type used as part of EIFS. Mineral wool, recently introduced in the U.S. market after being used in a limited capacity in Europe and Canada for several decades, is another insulation board option for EIFS. In either case, location of insulation board joints needs to be coordinated to ensure proper bond pattern/overlaps, L-shaped cuts around openings, butt joints, conflict with aesthetic reveals, and more. Note that EPS and mineral wool have different design and installation considerations. For instance, EIFS with mineral wool requires the integration of a supplemental mechanical attachment and cannot be shaved to eliminate planar irregularities. Depending on the backup wall and extent of planar irregularities, mineral wool may require thicker and/or multiple applications of the base coat material and/or heavier textured finish materials. These additional steps that can impact the installed cost and should be taken into consideration.
Base Coat
The most common base coat applied to the surface of the insulation is a polymer-modified cement-based material, which can also serve as the adhesive. Ready-mixed acrylic-based materials are also available, though not as common. Different base coats can have different properties and functions. For instance, a high build base coat can help resolve planar irregulates. Some have waterproofing characteristics that are helpful for applications like skyward facing sloped surfaces like projections, deep reveals, and more.
Reinforcing Mesh
Reinforcement mesh is embedded in the base coat layer or installed in multiple layers. It’s specifically designed for EIFS to provide reinforcement and impact resistance. Different mesh types and layers can be added for enhanced impact resistance where necessary, like at near grade conditions, balconies, and so forth. Typically, diagonal strips of mesh are installed at high stress concentrations like at corners of window or door openings. It’s critical that the mesh is part of the manufacturer’s tested system, since the mesh has material properties necessary for performance, including alkalinity resistance, fire-resistance, and more.
Finish Coat
The finish coat is applied over the base coat and provides a decorative, durable, crack-resistive finish with an array of different colors, textures, and performance properties. There are different products available to help achieve aesthetic goals while optimizing performance. Applying a primer that’s pigmented to match the finish coat layer, for example, can help create color uniformity and effective coverage. Darker colors can be prone to premature fading, so it’s a good idea to choose products that help minimize maintenance. You can also select products that help minimize staining in areas of the building that may stay wetter longer, like at north elevations and shaded elevations, for instance.
It’s important to work with qualified installers to achieve a high-performing EIFS system. Contact IMI for additional guidance on designing and installing EIFS.
