Rainscreen cladding assemblies’ functionality is based on the “perfect wall” concept developed by building scientist Joseph Lstiburek. Masonry cavity walls are widely considered to be the original rainscreen assembly. Much of that is due to the system’s ability to accommodate continuous insulation while simultaneously providing substantial moisture control. Rainscreen walls can be designed with both open and/or closed joints which allow primary bulk water deflection and protection via the facade surface itself. Like many cladding systems, rainscreens are designed with secondary water and moisture control layers. These layers allow any moisture that either penetrates the cladding or accumulates as a result of condensation behind the cladding to evacuate and dry via air convection. Moisture is further restricted from entering the building interiors by the air/vapor barrier (AVB), which is commonly applied behind the insulation and on the surface of the sheathing and/or backup wall structure. Most rainscreen wall claddings are held off the backup wall surface by specifically designed steel or aluminum sub-framing systems, which provide mechanical anchorage and the necessary space for insulation and air circulation.
Masonry cavity walls are widely considered to be the original rainscreen assembly. Often, building scientists deem rainscreen wall assemblies the “perfect wall.” Much of that is due to rainscreen systems’ ability to accommodate continuous insulation while simultaneously providing substantial moisture control. In fact, many people select rainscreen systems because of their superior moisture resistance and control. Rainscreen walls allow bulk water deflection and removal via the facade surface itself. In addition, they allow water and moisture that gets behind the cladding to drain out and to dry via air convection. Moisture is further restricted from entering the building interiors by the robust air/vapor barrier (AVB), which is commonly applied behind the insulation and on the surface of the sheathing and/or backup wall structure. Most rainscreen wall claddings are held off the backup wall surface by specifically designed steel or aluminum sub-framing systems, which provide mechanical anchorage and the necessary space for insulation and air circulation.
Rainscreens aren’t included in the 2021 IBC, and as such currently have no code prescriptive requirements. Because of this, local building inspectors generally don’t check specific assembly and building details of rainscreen assemblies in the field. Quality assurance is critical for rainscreens, which are often proprietary designs and products. Trained installers know they must follow manufacturer guidelines as well as approved shop drawings.
Many rainscreen details differ from one project or manufacturer to the next, so craftworker crews must be experienced and careful. Masonry and tile contractors have been installing rainscreen systems successfully for many years, and have the know-how, tools, and equipment needed to get the project built right the first time.
Modern rainscreen cladding assemblies have unique components but follow basic masonry veneer concepts familiar to mason contractors, such as provisions for moisture, movement, thermal control, and structural integrity. For example, when metal sub-frames are used to support rainscreen claddings, masons are trained to install them to maintain continuity of the water/air control layers on the back-up wall while locating the clips and rails to properly engage the back-up wall and masonry veneer units. After the metal sub-frame system is installed, the masons then install continuous insulation around the veneer anchors, as is typical for any masonry veneer installation. Lastly, masons are the perfect trade to install masonry cladding materials because they understand common masonry procedures of how to safely move, handle, and cut masonry material on the jobsite, are familiar with level and humoring work, and have access to appropriate scaffolding and other masonry related tools to realize installation efficiencies.
