ANTIMICROBIAL CHARACTERISTICS OF COPPER-BASED HARDWARE

Photos courtesy of Rocky Mountain Hardware

These are examples of the range of antimicrobial copper alloy hardware and accessories that can be produced using bronze products to kill bacteria.*

As a result of the COVID-19 pandemic, there is a renewed interest in keeping public spaces clean and safe from the spread of disease. There are a number of ways to go about this in buildings, but there is one very successful approach based on using antimicrobial materials wherever people need to touch a surface. This approach has been recognized and registered with the U.S. Environmental Protection Agency (EPA) based on field testing as well documentaton in more than 40 peer-reviewed and professionally published papers. The material that has received the most attention is a copper-based metal alloy that may take several forms, such as different types of bronze or brass. These copper-based metal alloys have been shown to be the only class of solid material with the inherent ability to kill bacteria harmful to human health.*

The science behind these results suggests that copper surfaces affect these bacteria in two sequential steps. The first step is a direct interaction between the surface and the bacterial outer membrane, causing the membrane to rupture. The second is related to these rupture holes in the outer membrane, through which the cell loses vital nutrients and water, causing a general weakening and death of the cell. Based on these results, bactericidal copper alloy is the only class of solid surfaces (i.e., not a liquid or gas that EPA has recognized) that is registered with the EPA and capable of supporting public health claims of killing harmful bacteria that pose a risk to human health.* No other solid-surface material, no coating, nor any additive has this kind of registration and can currently support any such claims.

When bactericidal copper alloy is used as the material for producing hardware and accessories, these products carry the same ability to kill the tested bacteria. The installed hardware can be used in a conventional manner, meaning that door handles, pulls, door plates, etc. that people need to touch on a regular basis to operate doors still function in the usual manner. Similarly, cabinetry can be equipped with hardware made from antimicrobial copper for pulls and handles. And just as significantly, accessories such as hooks, shelves, switch plates, grab bars, and towel bars can be made of bactericidal copper alloy to help in those heavy-use locations as well. Other applications are possible too, including sink faucets and handles, handicapped door activation switches, and even custom-fabricated elements for particular needs in specific building designs.

Additional Bronze Hardware

Windows are another area where bronze hardware can be used quite successfully. The handles for casement, awning, or European-style tilt/turn windows can be made from bronze, as can hardware for double-hung, sliding, and other window types. Coordinating the style and color with door hardware can be an effective and sometimes unexpected way to create design continuity within a building.

There is also the opportunity to use bronze in a variety of other discreet ways in multifamily housing. Bronze accessories are available for things such as apartment/unit door numbers and mail slots, or signs for common public spaces like restrooms. For stairways, handrail brackets and balusters can be used that can match or complement other bronze hardware. Carrying this a bit further, even electrical switch plates and outlet covers are available in bronze to create a very coordinated look.

Not to be overlooked, bathrooms, kitchens, and lighting fixtures can be considered too. Nonferrous bronze is ideal for any wet location since it does not oxidize (rust) the way that iron-based metals do. Faucets, sinks, shower controls, and other offerings fabricated from bronze overcome these issues and create striking visuals. Similarly, bronze lighting fixtures hold up extremely well outdoors and are available in a variety of artistic styles and looks for all locations.

Overall, bronze hardware, fixtures, and accessories can help unify and upgrade the design of multifamily buildings in a significant and sophisticated way to promote the look and appeal desired.

Expansion Joints

Large buildings, including multifamily buildings and their associated parking structures, often require expansion joints to control movement. When this is the case, there are several things to consider, including the following.

Type of Movement

Thermal movements are caused by daily environmental temperature changes in and around the structure. Thermal movement is primarily one directional in nature and is the result of the expansion and contraction of the building as it is affected by heat, cold, and humidity. Seismic activity is caused by shifting of the earth’s tectonic plates (i.e., earthquakes, tremors, etc.). Seismic movement in buildings may be horizontal, vertical, in shear, or a combination of all three. Wind-load-induced movement is caused by high winds forcing the structure to sway. Wind-load-induced movement is normally perpendicular and/or parallel to the joint. This is common where a low horizontal building span meets with a taller vertical element, such as the communal space of a multifamily building adjacent a high-rise component.

Nominal Joint Size

The nominal joint size is the designed width of an opening at a median temperature as dictated by the structural engineer. The expansion joint system selected needs to accommodate the minimum and maximum dimensions of the movement range for the given joint width. For thermal concerns, this means the joint needs to move at least 25 percent in both directions (e.g., a 4-inch joint needs to be able to shrink to 3 inches or expand to 5 inches at any given time). For seismic and wind-load concerns, the joint needs to be able to move 50 percent in either direction (e.g., a 12-inch joint needs to be able to shrink to 6 inches or expand to 18 inches at any given time). Note that seismic joint widths may increase with higher floor levels as well.

Joint Applications and Locations

The design of the project will determine whether it includes interior joints, exterior joints, or both. Typical interior application conditions of expansion joint systems include floors, walls, ceilings, and roofs. However, joints may be needed on exterior building veneers, soffits, parking decks, patios, and roofing systems as well.

Image courtesy of Inpro

Typical locations of expansion joint systems in building construction.

Loading Requirements

Different expansion joint systems have different capabilities to withstand the daily wear and tear of the building use. Floor joints in particular are subject to different types of traffic, such as pedestrians, equipment, or vehicular. The room location, such as a heavily used lobby or corridor compared to storage spaces or ancillary spaces, will influence the loading as either uniform, rolling, or concentrated. Consider the route for tenants to move their belongings in and out of a multifamily building. If there is an expansion joint in that location, it will be subject to repeated rolling loads.

Form and Appearance

Different expansion joint systems bring different appearances: some look simple and utilitarian, others include metallic covers, while still others can accept inserts of finish materials. Depending on the desired aesthetic, anodized metal finishes, Kynar coatings, or foam seal colors can all be considered to either complement the decor, provide an accent, or minimize its appearance. Final selection can be based on things like the room location, adjacent finishes, or simply the nature of the multifamily building.

Photo courtesy of Inpro

The form and appearance of expansion joints in multifamily buildings can vary based on the selection of type and materials.