Expansion joint cover systems are an important part of commercial construction. They provide structures with flexibility, allowing building movement to occur safely. They also support the required traffic, withstand the elements, provide life-safety fundamentals, and blend naturally with adjacent finishes. There are some nuances to selecting the correct product that make a significant impact on the success of the building project. Though identifying the correct product for a specific application may seem overwhelming, we’ve provided considerations that can help simplify the process.
1) Expected Joint Size and Movement
The first item to consider is how large the gap opening will be and the associated movement required in the building. This will steer the decision toward a set of products that meet that specific criteria.
Expansion joints will allow movement during temperature fluctuations, wind-loads, ground settlement, or even seismic activity. The nominal width refers to the width of the joint opening at a median size. Maximum width refers to how wide the joint is expected to open (also known as max open). Minimum width refers to how narrow the gap is expected to contract in size (also known as max close). The percentage of expected movement is used to determine the maximum and minimum widths.
A 2″ joint at ±50% movement indicates that the maximum width equals 3″ (the nominal width plus half the nominal width), while minimum width equals 1″ (the nominal width minus half the nominal width). Most Balco systems can withstand movement from ±50% percent to up to ±100 percent!
Another important consideration is the movement of joints that are perpendicular to each other, such as at a corner. When this occurs, one of the joint covers will need to laterally shear when the other opens and closes. If there are large amounts of movement expected, care will need to be taken in the design of transitions to handle lateral shear movement and maybe even vertical shear movement. (For this reason, when possible, joints should run continuously through the building without changing direction). The capacity for shear movement varies by product.
2) Interior and Exterior Considerations
The second item to consider is whether the system is intended for interior or exterior applications and what sort of environmental conditions apply — like weatherproofing.
Interior expansion joints do not typically require a weatherproofing moisture barrier as exterior expansion joints do. Occasionally, they require a hygienic barrier to prevent contamination in locations such as large commercial kitchens, food storage, prep areas, food manufacturing and packaging, surgical rooms, clean rooms, and laboratories. This is critical for health and safety reasons. A moisture barrier can be added to any interior cover, upon request.
Exterior expansion joint systems (found in roofs, walls, parking garages, outdoor stadiums, etc.) are exposed to all sorts of weather conditions. Exterior covers typically feature both primary and secondary moisture barriers (often in tandem with a building’s envelope system) to prevent intrusion of and wear from the elements (condensation, rain, snow, ice melt, UV exposure, hot temperatures, wind, dirt, flying debris, etc.). The appropriate material for the expansion joint system (whether a robust metal plate or durable face seal), along with its proper weatherproofing, ensure proper longevity from the brutal effects of Mother Nature.
3) Load Capacity
Expansion joints for the floor must be able to easily accommodate a variety of traffic conditions. One of the most common mistakes is that interior floors are often thought of as pedestrian-only applications without the consideration of other factors, like heavy food or beverage carts or scissor lifts and maintenance equipment. Irreparable damage can occur when heavy equipment comes into contact with systems designed for pedestrian traffic only. Floor expansion joint systems, whether interior or exterior, range from pedestrian design load to up to vehicular loads like those used for parking applications.
An important consideration when determining design loads is their capacity to allow the minimum live loads defined by IBC Table 1607.1., established primarily for flooring and supporting structure. Balco has developed a load-bearing technical guide (Balco’s Load Data Sheet) that considers both the size/type of load and the “load contact area,” an often overlooked consideration. A small load contact area runs a higher risk of stress and deflection due to unanticipated heavy loads.
4) Fire Rating Considerations
Both interior and exterior expansion joint systems often need to be fire-rated. Fire and smoke barriers help contain fire or smoke damage to a restricted area within the building or from spreading to an adjoining structure or building. Any fire-rated expansion joint assembly installed will also need to be of the same fire rating as the adjacent fire-resistant materials of the floors, walls, ceiling, roof. Fire and smoke barriers’ placement is either below (as in floors, roofs) or behind (as in walls, ceilings) expansion joint systems, they are designed to also accommodate the same movement as the expansion joint (up to ±100 percent), and they carry fire ratings up to four hours.
5) Expected Placement and Adjacent Constructions
It’s important to consider the adjacent construction materials, including wood, drywall, concrete, tile, CMU, and carpeting. These materials, the location, and the functionality affect which type of mounting will be used. Options include surface mount, recess mount, and flush mount. The type of construction — whether new, renovation, or new-to-existing — also impacts the type of mountings used. For example, concrete blockouts are often used in new construction to provide a recessed joint for a smooth transition.
The look of expansion joint systems often requires significant consideration, depending on the desired aesthetic result. Architects and owners can get creative and incorporate the expansion joint systems into the design in an obvious and stylish way. Or, they can make them as seamless as possible to blend in with the adjacent building material.
Elastomeric materials, which are often an integral part of expansion joints, are available in extruded silicone, Santoprene or PVC and come in standard factory color options to complement surrounding building finishes. (Custom color options may be available for some systems).
Metal finishes, especially in aluminum or stainless steel, are the current trend for both exterior and interior applications and can be provided with polished, painted, powder-coated, or anodized finishes. Kynar paints can match or complement surrounding materials (while adding a layer of durability).
Expansion joint systems should not only perform well but also complement the building’s design. Balco offers endless possibilities to this end.
Selecting the appropriate products requires forethought and careful consideration of many factors. Including Balco in the earliest planning stages of a project is beneficial to all parties involved. We are always available to help address concerns and provide direction to ensure nothing is overlooked so that the right expansion joint system is a proper fit for the project at hand.