Ensuring Quality Installation

The installer, whether the MCM fabricator or an independent project manager, is responsible for safeguarding that each step of the installation process is properly completed. As part of the installation process, MCM fabricators are responsible for the coordination of material deliveries to the job site. They are also responsible for coordinating with individuals and companies from other trades regarding installation of the cladding system, and providing the materials and labor required to provide weathertightness for the designed system.

Final field measurements including framing/substrate tolerances and the “field” fabrication of panel components must be completed on-site. Final project closeout items are typically a joint effort between the MCM installer and the fabricator. The MCM installer typically provides warranties for the workmanship and installation, which we will discuss in more detail later in this article.

Images courtesy of Metal Construction Association

During installation, panels are routed and fabricated into formed pans with flexible exposed sealant applied at each panel and attached to interlocking or clip extrusions to join, thus minimizing air and water infiltration.

Wet-Seal, Dry-Seal, and Rainscreen Systems

Since MCM products were introduced to North America, installations have been performed using three different styles: wet-seal, dry-seal, and rainscreen systems. These systems have been utilized on many hundreds of different types of buildings. Variations of these systems are still commonly used today. Regardless of the installation system used, the primary goal is to ensure that exterior cladding and/or rainscreens prevent unwanted air and moisture from breeching the building envelope.

All of these systems are required to meet certain performance requirements, which can include air infiltration (ASTM E 283), water resistance (ASTM E 331), structural performance (ASTM E 330), and specific rainscreen requirements identified in AAMA 508 or 509 for these type of systems. All installations where panels are used in excess of 40 feet must meet the fire-protection requirements of NFPA 285.

Wet-Seal System and Testing

The wet-seal system is also known as a “single-line barrier wall” or “fully sealed wall” because there is a joint located between adjacent panels that is fully sealed with sealant. Silicone or a medium modulus sealant are typically used to fill this joint. These sealant types are used because they are flexible and will remain adhered to the panels as they move due to thermal expansion/contraction.

During this installation process, a single barrier is created between the exterior environment and the cavity behind the panel. Panels are routed and fabricated into formed pans and anchored to the substrate using extrusions. The joints are sealed with exposed sealant to minimize air and water infiltration.

The proper installation of sealant and adhesion to the panel is critical to keeping unwanted air and water out of the building. This installation must be inspected regularly to ensure that the sealant remains flexible and adhered to the panel. This is especially important as the exterior envelope ages. While this system is designed to stop water infiltration at the exterior panel surface, any condensation that makes its way into the panel cavity can still cause issues for the building interior and materials. A properly designed and installed panel system should have openings for cavity moisture to exit via weeping or evaporation without entering the building.

No additional testing is required for wet-seal systems other than the aforementioned air-infiltration requirements tested to ASTM E 283, water-resistance requirements tested to ASTM E 331, structural performance requirements tested to ASTM E 330, and fire-performance requirements tested to NFPA 285.

Dry-Seal System and Testing

Dry-seal systems do not use exposed wet components, such as sealants, in the panel joint design. The dry-seal system has a few more components when compared to the wet-seal system. MCM panels are formed into pans and joined with aluminum interlocking extrusions and/or gaskets. The infiltration of water is primarily controlled by the interlocking aluminum extrusions. Just like properly designed wet-seal systems, dry-seal systems allow for any water or condensation that finds its way into the panel cavity to drain or evaporate out before penetrating the building envelope. The type and location of an air/water barrier should not have an impact on the panel performance of a dry-seal system.

Dry-seal systems allow for a panel reveal from ¹⁄₂ inch to 12 inches. Joints can be finished with color matched or complementary accent strips to provide a sleek, clean, and aesthetically pleasing exterior.

When hiring a fabricator to provide and/or install a dry-seal system, it is important to ensure that it completes the same basic ASTM E283, ASTM E331, and ASTM E330 testing to ensure proper performance.

Raincreen Systems and Testing

Rainscreen encompasses two basic categories of systems: drain/back ventilated (D/BV) and pressure-equalized rainscreen (PER).

Both systems employ open joinery and allow a controlled amount of water into the wall cavity and between the outer and inner leafs. D/BV systems rely on the ventilation cavity to both drain and dry out any residual water.

PERs also employs a ventilation and drainable cavity but add compartmentalization, limiting the amount and duration of a pressure difference between the exterior environment and the air cavity behind the cladding. Compartmentalization of the wall cavity facilitates rapid pressure equalization.

Rainscreen systems allow for a panel reveal from ¹⁄₂ inch to 12 inches depending on the type of system and the required performance. Joints can be finished with color-matched or complementary accent strips to provide a sleek, clean, and aesthetically pleasing exterior.

The performance of all D/BV and PER systems rely on properly selected, detailed, and installed air/water barrier appropriate for the project’s climate zone. Air/water barrier imperfections introduced into the system test (AAMA 508 and 509) create a worst-case assembly that causes reduced pressure equalization.

As materials change and technological advancements are made, we have a better understanding of how exterior cladding and MCM products perform under loads and in severe weather conditions. These new developments are regularly incorporated into design and manufacturing processes as well as building codes.

Warranty Information

Nearly all MCM products and services come with some type of warranty. Not only are warranties available on the manufacturered products, but oftentimes a separate warranty is available on the work done by the fabricator and the installer. Warranties vary, so it is important to confirm all material and system warranty information with the manufacturer or fabricator prior to specifying and installing materials. Confirm terms other than the length of the warranty, as different finishes warrant different performance.

Because services and warranties vary by each MCM manufacturer, fabricator, and installer, it is important to review all warranty information early in the planning process.

Conclusion

MCM products produced by a quality sheet manufacturer, engineered and fabricated by a quality fabricator, and installed on the building by a quality erector provides superior building protection, a beautiful architectural facade, and a long-lasting building exterior for many years.

Jessica Jarrard is an independent writer and editor focusing on health, science, and technology. She contributes to continuing education courses and publications through Confluence Communications. www.confluencec.com