Facade Specialty Details

When it comes to facade design, the one thing that is certain is that there will be design and construction details to address. Those details can include connections, attachments, joints, or other conditions. Two things in particular deserve some attention here which are very common elements of many commercial building designs—expansion joints and architectural louvers in openings. Both of these elements can have a significant impact on the successful functioning of a facade in terms of the purpose they are intended to serve plus their integration with the surrounding facade materials. Additionally, they can have either a positive, negative, or neutral impact on the overall building design scheme depending on how they are handled. With the above in mind, let’s take a closer look at each of these specialty conditions.

Facade Expansion Joint Covers

Most commercial buildings of any size require expansion joints between sections of the structure to allow a building to expand, contract, or shift laterally due to imposed forces. Those movements can come from temperature changes causing materials to expand or contract, winds that move or sway the building, settlement over time, or seismic events. A well-designed series of expansion joints will allow sections of the building to move independently of each other without damaging either the structure or the finish materials.

Of course, leaving an expansion joint open to the elements on a facade is not a realistic solution. Hence, those joints need to be covered in a manner that maintains the integrity of the joint and the facade, both for appearance as well as performance, while still allowing for independent building movement on either side of the joints. Metal expansion joint covers are typically manufactured to allow for the anticipated building movement by using components that are designed to slide or otherwise pass by each other or adjacent building portions. The means to do that will vary by manufacturer and by type of expansion joint cover, and manufacturers typically provide a range of product offerings to suit different conditions. Selecting the proper one will help assure that the building and the facade are protected from damage when, or if, building movement occurs.

In addition to allowing for movement, these expansion joint covers also need to be able to insulate and protect the joint opening from outside elements. If water or moisture make their way into the joint opening, then the building could be susceptible to leaking, moisture damage, mold, or other deterioration which could cause failure. Therefore, metal covers with a water and vapor barrier installed behind the cover are common, as are fully watertight solutions that fit into a joint opening. Similarly, if airborne dust, dirt, or other objects get in behind the expansion joint cover, then it may not function properly since the anticipated movement or sliding of components could be impaired. Hence the expansion joint cover needs to seal against such penetration of foreign matter as well.

While the need for expansion joints and covers is clear, there is a design aspect that needs to be addressed. Often, the architect’s main design concern is focused on concealing expansion joint covers so as not to have a significant impact on the overall building facade design. Manufacturers have responded with multiple options for covers that can be infilled with whatever facade materials are specified for the rest of the building, thus creating a rather continuous appearance. The metal of the expansion joint cover itself can also be custom colored to match a building’s facade and become virtually undetectable.

When an expansion joint cover type is identified that meets the aesthetic criteria for a project, architects can then work with manufacturers to verify that the performance criteria is met. Some provide considerable technical assistance and, when applicable, they can conduct cycle testing on a joint cover to verify their performance. From that standpoint, architects should have confidence that the solution they specify will both perform well and blend into the overall facade design in a minimally invasive way.

Kevin Smith, PE, is the engineering manager at Construction Specialties and provides technical assistance to architects on a regular basis regarding expansion joint covers. He points out that “Many of our expansion joint covers have been reimagined over the years to accommodate architects’ demand for better integration with their designs. Each project that we work on is an opportunity for us to evaluate how to refine our solutions for better performance, resiliency, and concealment.” Clearly, then, there is an ongoing interest within the industry to accommodate project specific requirements that address all aspects of incorporating expansion joints successfully into a building facade.

Images courtesy of Construction Specialties

Expansion joints in a building facade are often necessary but need to be protected with an expansion joint cover. Selecting the best product involves meeting the performance needs of a project but can also involve selecting one that allows matching facade material to be inserted in the face of cover to blend with the overall design.

EXPANSION JOINT COVERS CASE STUDY

Photos courtesy of Construction Specialties

Project: De Young Museum
Location: San Francisco
Design Architect: Herzog & de Mueron
Principal Architect: Fong & Chan Architects

The Project: Due to the 1989 earthquake damage and the findings in 1993 that more earthquake damage would occur, the de Young Museum’s board of trustees agreed to rebuild the museum as a state-of-the-art facility. This included the use of a base isolation system that would allow for extreme seismic movement of up to 42 inches in any horizontal direction.

The Design Challenge: While seismic performance was a primary consideration, this very high-profile project also required the concealment of any large seismic joints on the exterior. The typical means to conceal such joints is to use an expansion joint cover, usually treated with a metallic finish for durability. However, a major consideration of the de Young project was that the expansion joint covers must be “virtually invisible” within the museum’s weathered copper skin.

The Design Solution: Architects Fong & Chan and Herzog & de Meuron designed a facade that incorporated a unique copper skin that is purposely riddled with inconsistencies in order to enhance the material’s natural ability to oxidize. Recognizing that a number of seismic joints were going to be needed, they reviewed the options available and ultimately specified a seismic joint cover system that could allow the same copper material as the rest of the facade to be inserted into the expansion joint cover. This allowed them to achieve a building skin that seamlessly incorporated the needed seismic joints into the facade’s copper panel frame. The finished product allowed the joints to be virtually invisible beneath the museum’s one-of-a-kind skin but also provided the necessary seismic function. The seismic joint covers used employed a unique gravity closure concept that allows the cover system to open and move during an earthquake and then reset automatically afterwards. Typically, expansion joint covers for this type of system range from 8 to 34 inches wide, but for this project, covers up to 60 inches wide were needed and successfully created.

Results: The gravity based seismic expansion joints and covers allow for the movement of the building when needed but with no impact on the museum appearance or overall functionality.