System Coordination

If an expansion joint is needed on a facade, it very likely needs to continue across the roof and other adjacent planes of the building as well. It is often the points of transition like these that are the source of problems and failure of the system─meaning air and water leakage potential, fire breaching, etc. Therefore, the ideal situation is to select a system that is already designed and manufactured to make the transition so a properly sealed, continuous joint cover system can be installed. It is of course also very helpful to have the manufacturer provide a full complement of CAD and BIM files so the details of the expansion joint system can be worked directly into the facade design and properly coordinated with other materials and systems.

In order to address this need, there are new products available that include coordinated wall and roof expansion joint systems with pre-designed transition caps for all types of changes in joint direction. Since both the wall and roof systems are designed and manufactured together, they work well in the field together too. This is a significant improvement over the traditional industry approach of matching the wall expansion joint with a dissimilar system on the roof. Installing two very different expansion joint systems on a building ultimately makes addressing all the changes in planes more difficult and usually requires project-specific solutions each time. A coordinated, modular-based manufactured system can wrap up, over, around, and back down the entire facade and roof with one continuous system that makes design implementation much easier. It is also possible to pre-assemble the covers to the greatest degree possible such that the installation is also simplified resembling simply hanging a door on its hinges. This approach also ensures repeatable results in quality, consistency of substrate requirements, a distinct reduction of field labor costs, and reduced time for workers on roof edge conditions or on scaffolding. A range of high-performance waterproof membranes can be coupled with this adaptable system such as insulated moisture barriers (for moisture and thermal control), reinforced, two-ply, 45-mm-thick EPDM sheets, (weather protection only), or flexible TPO or PVC membranes (for chemical compatibility with adjacent skins).

Images courtesy of Inpro

A coordinated expansion joint system that can transition seamlessly from facades to roofs and other adjacent surfaces can reduce the potential for problems or failures at the transition points.

Fire-Resistive Joint Systems

In many cases, expansion joints are installed in construction that need to maintain a fire-resistive rating across the joint. Since building expansion joints in floors, roofs, or walls create a pathway for fire and smoke to travel through, it is useful to recognize that a range of third-party tested joint solutions are available.

Expansion joints are tested under a rigorous three-tier testing classification called UL2079 - Test for Fire Resistance of Building Joint Systems. This encapsulates the burn characteristics of ASTM E119 (Surface burning) and the joint cycling of ASTM E1399 in a similar fashion to E1966 and is immediately followed by a hose-stream test for any vertical applications. These tests are designed to essentially replicate a seismic event with ground shaking (cycle test), broken gas lines, and electrical fire (oven burn, 120, or 180 minutes at 2,000°F) then control of the fire (hose stream test). If at any point during this testing, flames escape through the joint product, or if the temperature climbs too much, or if any smoke whatsoever makes its way through, then the product fails. Period. In order to pass, the manufacturer needs to re-design and re-test the product until it passes.

Beyond basic product testing, the International Building Code (IBC) references the need for entire facade assemblies that use combustible elements to show additional fire resistance following NFPA 285 “Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components.” This standard looks at the entire wall assembly, not just individual products for code compliance, and it was developed in response to building fires where combustible foam insulation was used in the facade design.

Note that there are three fundamental types of fire-rated joint systems. The first is to use compressible foam products that have been shown to achieve appropriate fire ratings. A manufactured fire-rated pre-compressed foam material that is totally impregnated with fire retardant will maintain the specified and tested fire-rated assembly even if the facing has been damaged. Another option is mineral wool and intumescent sealants, which are extremely simple to install and very cost-effective. However, they can only be deployed on narrow joints of 1-3" [25-75mm] and only allow for 20 percent (+/-) joint movement. A third fire-resistive product is based on the use of fire blankets. These are the most versatile systems, suitable for expansion joint gaps of 2 through 32 inches and able to withstand high rates of movement. Fire blanket systems come in two forms—either ceramic cloths with intumescent layering or graphite sheet goods encasing insulating blankets. In seismic conditions, they allow for approximately 50 percent (+/-) of joint compression and expansion movement. Some models are able to retain their rating through lateral shear movement testing while others cannot. Fire blankets are tested in concrete on horizontal decks; however, any tested and rated fire-rated deck assembly is acceptable as the joint only addresses gap protection. Walls are typically tested in steel studs and Type X gypsum, however similarly to the floors, any properly rated wall system (CMU, shaft walls, etc.) is acceptable.

Note that fire blankets can be specified either to withstand water or not. Those that cannot withstand water exposure and become wet are often rendered useless against smoke, fire, and heat - even after re-drying they carry diminished fire resistance. Products that are rated and tested for water exposure during or after construction or for open structures such as parking facilities and stadiums, provide fire protection even if they become wet. It is important then, to select and specify the appropriate material for the water conditions anticipated in the building.

CONCLUSION

Facades require design attention at the large scale and the detail level. That includes everything from the materials used, the approach taken to sustainability, the incorporation of expansion joints where needed, and the coordination of the facade design with other building planes. Expansion joints in particular require an understanding of the forces and conditions that need to be addressed as well as information related to available products and systems just like other components of the facade. Using BIM has been shown to be a very helpful and effective means to address the need for the design and coordination of facade elements. Of course, the strategies, features, and ideas presented here behind using BIM as a tool for designing a facade are certainly not all-inclusive. There are clearly many other advantages and opportunities that BIM tools can provide in developing, implementing, and creating better facades that are integrated, efficient, and sustainable. The combination of physical data with the visualization of component parts and the integration of the whole design for sustainability purposes is the launch pad for creating better building designs and more successful facade designs.

Peter J. Arsenault, FAIA, NCARB, LEED AP is a nationally known architect and a prolific author advancing better building performance through better design. www.pjaarch.com, www.linkedin.com/in/pjaarch