This article takes an in depth look at mezzanines.
You will learn:
A mezzanine refers to an intermediate level positioned between the main floor and the ceiling within a building. This level is typically partially open to the main floor below, with a lower ceiling and stretching over the main space without fully covering it. Mezzanines might be freestanding, suspended from the ceiling, or permanently integrated into the building's design.
Often, mezzanines are perceived as the floor situated above the initial ground level. They can be either permanent fixtures or temporary installations, serving multiple purposes such as additional office space, storage, or work platforms. These versatile structures can be set up in various places and configurations, ranging from outdoor platforms for improved access to extra levels within a workspace.
Freestanding mezzanines, as depicted in the diagram below, provide versatility as they can be effortlessly dismantled and relocated.
The term "mezzanine" can sometimes be misleading, as it applies to both lasting and temporary structures. Permanent mezzanines are those built into the original framework of a building using materials like concrete and steel, and they are incorporated into the building inspector's classification while being subject to regular inspections.
Conversely, mezzanine decks or work platforms are not meant to be permanent structures. They are installed post-construction to cater to the growing space needs of a company. As such, these mezzanines are seen as temporary solutions rather than integral components of a building's structure.
To differentiate between these types of mezzanines, consider their classification. Permanent mezzanines, which are integral to the building's original design, appear in a building inspector's report and require infrastructure like bathrooms and elevators, affecting the building's tax assessment.
Conversely, temporary mezzanines are regarded as equipment, akin to production machinery, and are documented in an inspector's report as such.
While temporary, mezzanines are crafted from robust materials like cold-rolled steel, hot-rolled steel, stainless steel, fiberglass, or aluminum. Flooring options for these structures include finished wood, steel, aluminum, or fiberglass grating.
Commonly, these structures are implemented in growing companies requiring additional space for storage, office setups, or work areas. Mezzanines offer an economical solution for space optimization, effectively doubling a building's usable floor area.
Typically found in warehouses, distribution centers, and factories with high ceilings, mezzanines make efficient use of the otherwise unused upper space. Industrial mezzanines come in various designs, including structural, roll-formed, rack-supported, or shelf-supported, to accommodate high-density storage needs.
When deciding to install a mezzanine, the primary consideration is the load requirement. While mezzanines generally have a similar design, the choice of construction materials varies based on the weight they need to support. Aluminum or fiberglass are ideal for lighter applications such as additional offices or light part storage, whereas steel or stainless steel is more suitable for supporting heavy equipment.
Free-standing mezzanines, also known as equipment platforms, are independent of the main building structure and offer the flexibility to be reconfigured as needed. They feature a securely anchored base, ensuring stability while allowing for easy relocation or repositioning. Supported by columns and bolted to the floor, these mezzanines occupy minimal space and are ideal for scenarios where the area beneath the mezzanine needs to remain accessible.
Rack-supported mezzanines are lightweight and provide the option to include a catwalk along with additional storage space. They are a cost-effective solution for expanding storage capacity. Unlike traditional mezzanines supported by structural legs, rack-supported mezzanines are supported by rack uprights. The mezzanine’s framing, including joints and stringers, bolts to these columns, enhancing the stability and anchoring of the decking. The close proximity of racks and shelves supports the overall structure, ensuring a stable and secure platform.
Catwalk mezzanines are used to increase the capacity of tall shelves or racks. The upper area of arack is accessible from catwalks that extend from the floor of the mezzanine. Existing shelving provides support for the mezzanine frame. Support columns can be added to offer additional support between the shelves. Catwalk mezzanines are a variety of shelving and rack supported mezzanines.
Catwalks primarily serve as walkways for accessing conveying systems, machinery, hoppers, silos, and attic spaces. Similar to mezzanines, catwalks utilize overhead space, converting it into secure and safe pathways for various purposes. They can be either self-supporting, like a free-standing mezzanine, or suspended from ceiling mounts.
Full mat mezzanines represent a hybrid of shelf-supported and rack-supported mezzanines. They integrate elements of both free-standing and catwalk designs, being supported by shelving or rack uprights. As illustrated in the diagram, the space above the shelving remains open, allowing for bulk storage, office areas, or employee cafeterias. Full mat mezzanines can be installed over existing shelving or rack systems.
Prefabricated, or modular, mezzanines come ready for use and are handy for quickly added extra space. They are free-standing and delivered ready to install to fit seamlessly into a work space. Prefabricated mezzanines are engineered for easy assembly and can be reconfigured when circumstances change.
Prefabricated mezzanines are commonly used for storage, offices, towers, and equipment platforms. Their ease of installation allows for rapid and cost-effective expansion of floor space. Generally more affordable and quicker to set up than custom-built mezzanines, prefabricated options also offer various heights, platform configurations, weight capacities, and beam and column arrangements, similar to custom designs.
Roll-formed mezzanines offer an economical and cost-effective storage solution, utilizing light gauge steel to create additional space. They are well-suited for commercial warehousing, retail stores, or locations where minimal interaction with forklifts or heavy lifting equipment is expected. These mezzanines can be quickly installed in various sizes to meet operational needs and their lightweight design allows for easy adjustment in response to changes in workload.
A structural steel mezzanine has steel beams and columns with metal decking for concrete or wood applications. Unlike roll formed mezzanines, structural steel mezzanines are heavier and a better option for shops and businesses that have large expansive production areas. They are made from high grade heavy duty steel that is durable enough for equipment handling and warehousing machinery.
Steel-fabricated mezzanines are commonly used in warehouses, equipment platforms, and industrial or manufacturing settings. The use of steel enhances durability, strength, and safety. These mezzanines can be freestanding and are bolted together to increase stability. Concrete flooring is often paired with structural steel mezzanines due to its high point load capacity and low noise levels.
Mezzanines are primarily used to create additional storage space and utilize the unused area beneath the ceiling. While this is their main function, the range of mezzanine types has expanded to accommodate a variety of applications.
Beyond providing extra storage, mezzanines can also serve as work areas for equipment or machinery in hard-to-reach locations. They can be designed to support chemical tanks, industrial pumps, sorting machines, conveyor systems, and even space capsules. The adjustable deck heights, load ratings, and deck layouts facilitate easy access for machine maintenance and specialized processes. Below are some examples of mezzanine applications.
Mezzanine offices provide a comfortable workspace elevated above the factory floor while occupying minimal floor space. They are ideal for supervisors who need to stay close to the manufacturing area but require an office for administrative tasks. By placing office space on a mezzanine, organizations can keep supervisory staff near the work area without interrupting the main production floor.
Mezzanines can be tailored to accommodate conveyor and catwalk systems, facilitating the movement of employees and inventory above the facility floor without disrupting work areas. Catwalks can be integrated to connect existing mezzanine levels and may be ceiling-hung or supported by the floor, adjacent structures, racks, or other mezzanines. Depending on the requirements and environment, catwalk surfaces can be either grated steel or solid. These systems also provide access between buildings and over machinery and equipment.
Equipment and work platforms create additional space for heavy equipment and can cover up to two-thirds of the main floor area. When both a mezzanine and an equipment platform are present, they collectively cover two-thirds of the main floor space and typically require a sprinkler system. Work platforms are designed to support industrial equipment such as cranes, conveyors, material lifts, and pallet racks.
Equipment or work platforms are designed to support industrial systems and equipment like piping and are built with structural steel. They include features such as ladders, railings, handrails, kick plates, staircases, and gates. Unlike standard mezzanines, equipment platforms must be specifically engineered to handle the weight they will bear, as well as their height and other dimensions.
Companies aiming to integrate automation into their operations often face space constraints. Overhead steel platforms, as illustrated below, are designed to facilitate efficient material movement, thereby freeing up the ground floor for time-sensitive and operationally critical processes.
Mezzanine flooring is widely used in retail environments to create additional display areas for products. By significantly increasing usable space and improving shelf capacity, mezzanines help boost sales and profits with a relatively modest investment. Their flexibility is further enhanced by the fact that they can be dismantled, relocated, or removed when no longer needed, adding to their overall value.
Workshops often face challenges when large orders exceed their available space. Mezzanines provide a flexible solution to accommodate increased demand without the need to relocate or rent additional sites. By moving shop congestion and overflow to a mezzanine, workshops can enhance efficiency and boost productivity. Affordable for small workshops experiencing sudden business growth, mezzanines are ideal for managing large orders and adapting to fluctuating needs.
Equipment platforms are designed for efficiency, convenience, and immediate access. Similar to catwalks, they provide clear and unobstructed access to equipment for monitoring, maintenance, and operation. These platforms can be designed to surround a piece of equipment or stand adjacent to it. They are typically freestanding and constructed from either roll-formed metals or structural steel. In addition to supporting equipment, these platforms can be utilized in facilities with tank and silo storage to manage and regulate capacities and structures.
Mezzanines provide a cost-effective solution for maximizing the use of available space and utilizing areas beneath the ceiling. As businesses expand and require additional office and work areas without the expense of constructing an addition, mezzanines and platforms offer a practical alternative.
However, while mezzanines present various advantages, it is crucial to recognize potential safety hazards. Improper installation and use can lead to significant risks, including injuries to employees and damage to equipment. It is essential to consider several factors when installing a mezzanine.
Like any construction, mezzanines must comply with specific building codes and regulations. Typically, each state has its own set of codes, in addition to those from the Office of Safety and Health Administration (OSHA) and the International Building Codes (IBC).
Mezzanine suppliers and manufacturers are committed to adhering to these safety codes to ensure the well-being of their customers.
Much like fire exits in a building, staircases leading to mezzanines must never be blocked or cluttered. Obstructed access can cause workers carrying equipment to fall or be injured. Employees must be properly trained on how to use the mezzanine and recognize its associated risks. As a safety precaution, stair widths are required to be 36 inches wide and feature skid-resistant diamond-plated treads.
All mezzanines have specific design specifications. When a side is exposed, appropriate guardrails must be installed to ensure safety.
The building floor must be capable of supporting the weight of the mezzanine. Typically, buildings have floor slabs that are six to eight inches thick, which can support up to 25,000 lbs. However, if the building is situated on sandy soil or has a high water table, it may not be able to support a mezzanine.
There is no universal load capacity for mezzanines. The weight a mezzanine can support and its load limit are defined by local building codes and manufacturer specifications. To comply with weight limit requirements, a mezzanine must be able to sustain its load across the entire deck area.
When assessing the weight that will be placed on a mezzanine, consider factors such as the equipment, office space, and the number of people along with their weights.
Local and federal building codes apply to mezzanines. Manufacturers diligently ensure compliance with all relevant regulations during the installation process. They also provide posters and notices for display in the work area to inform employees of mezzanine rules. Non-compliance with these codes and regulations can result in fines and potential facility shutdowns.
A mezzanine should be positioned as close as possible to the work area it serves to minimize the time workers need to access it and to avoid unnecessary movement across the facility. When planning for future growth and expansion, consider whether the mezzanine may need to be relocated or enlarged to accommodate changing needs.
Openings in mezzanine guard rails pose fall hazards, which can be effectively mitigated using safety gates with a dual-gate system. Tri-sided gates, for example, feature two gates: the first gate opens to allow loads to be dropped, while the second gate remains closed to ensure employee safety.
The appropriate type of safety gate is determined by the materials and equipment used on the mezzanine and the pallet drop area. For instance, when overhead hoists are employed near the mezzanine, a gate with an open top is ideal. This design allows products to be lifted onto the deck through the open space, while the employee remains protected behind the gate.
The number and type of gates required depend on their intended use. For instance, when overhead hoists are used near the mezzanine, a gate with an open top is suitable. This design allows products to be lifted onto the deck through the open space while keeping employees protected behind the gate.
Several safety gate models offer fall protection, including roly, pivot, clear aisle, and self-closing gates. The choice of gate should align with the specific use of the mezzanine and ensure adequate protection for employees.
Below is an example of an open-top safety gate.
When planning to install a mezzanine, several key factors need to be considered. The most crucial aspect is determining the intended use of the mezzanine—whether it will be for office space, storage, manufacturing, or equipment placement. The following information outlines important considerations to keep in mind as you plan your mezzanine installation.
The size and intended use of the mezzanine are critical factors that determine its required weight capacity. Typically, mezzanines are constructed to maximize available space.
Determining the purpose of the mezzanine also involves deciding its size. The dimensions and floor plan are usually dictated by the available space. Once the purpose is clear, you need to design the floor plan and plan the placement of personnel, walls, and equipment.
After installing the mezzanine, it is crucial to assess how it will enhance your operation and improve efficiency. The goals you set for the mezzanine will help determine whether additional components, such as hoists, racking, or shelving, are necessary.
The weight load capacity of a mezzanine floor is measured in kilonewtons per square meter (kN/m²). The intended use of the additional space will determine the required weight loading. General guidelines for weight loading are as follows:
Most building slabs are six to eight inches thick and can support up to 25,000 lbs. Before selecting the type of mezzanine, engineers will carefully evaluate the soil composition beneath the building to ensure a safe installation. The slab's capacity will influence the types of columns and footings required to support the mezzanine.
OSHA regulations require that mezzanines be at least seven feet above the floor to provide sufficient clearance for individuals. When designing a mezzanine, it is essential to consider how the additional space will be utilized.
Safety is a critical consideration in mezzanine design and depends on its intended use. If the mezzanine will be part of the manufacturing process, the type of handrails or guardrails will be selected based on employee safety. Building codes specify the types of stairways required, which must include handrails and diamond-patterned steps, as shown in the image below.
Mezzanine floors are composite engineered wood, plywood, particle board, steel, grating, diamond plate, or concrete.
The design of a mezzanine must comply with all building code requirements, especially in West Coast states like California, Oregon, Washington, Utah, and Nevada, where Seismic Zone regulations apply. A properly designed mezzanine adheres to IBC codes, AISC & ASTM standards, and OSHA requirements. The International Building Codes (IBC) govern most parts of the United States, and all mezzanine projects must meet these IBC requirements.
In some cases, customers may need to adhere to OSHA codes, including the ASA minimum requirements for stairs and railings.
A well-engineered and designed mezzanine accounts for all necessary variables to ensure it meets space requirements and qualifications. An over-designed mezzanine may include excessive features and use inappropriate or unnecessary materials, while an under-designed mezzanine could risk structural failure and potential collapse. A properly designed mezzanine uses the minimum amount of steel required to achieve the desired capacity. The goal is to maximize material efficiency, optimizing strength with the least amount of material needed to reach the required load-bearing capacity.
While all mezzanines share basic elements, their configuration and installation can vary based on their intended use. When considering the purchase of a mezzanine, it is crucial to understand the fundamental requirements to effectively discuss installation with a supplier. Below is a brief overview of key facts about mezzanines.
Framing is essential for providing proper support to the mezzanine. Various types of framing include:
C-section framing can span a wide range of distances and is versatile enough to be used in various applications without limitations on size or type.
Beam and C-section framing can span more than 20 feet in one direction while keeping the structural depth to a minimum. This combination is used in mezzanines of all sizes.
Beam and beam framing is used for heavy loads or for spans that are unusually long.
Beam and bar joist framing is used for medium to large mezzanine projects requiring wide spans and high load capacities.
Bar joist and girder joist framing are open-web systems used in large projects or for spans requiring high load capacities.
Handrails on stairways must be 36 inches high from the stair tread. They should be welded and feature a smooth, continuous finish.
A guardrail prevents individuals from falling over the edge and must be at least 42 inches high.
PSF (pounds per square foot) determines the design load or uniform load as specified in Table 1607.1 of the IBC Code. The minimum design load for mezzanines or work platforms is 125 PSF. Most applications do not require a uniform load greater than 125 PSF. For example, a 50′ x 50′ mezzanine with a 125 PSF load capacity can support up to 312,500 pounds, equivalent to 208 pallets each weighing 1,500 lbs. The PSF rating applies to the average load across the entire deck of the mezzanine, not to a specific spot.
Footings may be required if it is determined that the building's slab cannot support the load. The decision to use footings is made by the design engineer, who will review the building's original blueprints to assess the slab's capacity.
Each coding agency employs a different method for determining stair runs.
Steel, stainless steel, aluminum, and fiberglass are commonly used materials in the construction of mezzanines.
Building codes provide the fundamental guidelines for determining whether a mezzanine is classified as an intermediate level or a separate floor of a building. The primary regulating agencies are the International Building Code (IBC) and the Occupational Safety and Health Administration (OSHA). Both agencies have similar definitions of what constitutes a mezzanine.
The International Building Code defines a mezzanine as:
“A mezzanine is an intermediate level between the floor and ceiling of any story. In regard to the building code, mezzanines must comply with Section 505.2 of the International Building Code (IBC).”
According to Section 505.2 of the International Building Code, a mezzanine is considered part of the story above and does not need to be included in the building area or the total number of stories as specified in Section 503.1 when calculating the building size. However, while it is not counted in the building area, its square footage is included in determining the fire area. Additionally, mezzanines must be constructed from materials that conform to the building's Construction Type as outlined in Table 601.
The clearance height above and below a mezzanine must be at least 7 feet. Additionally, the total area of a mezzanine within a room cannot exceed one-third of the floor area of that room.
Occupants of a mezzanine must have access to at least two means of egress if the common path of egress travel exceeds the limitations specified in Section 1014.3. When a stairway is used as a means of exit access from a mezzanine, the maximum travel distance includes the distance traveled on the stairway, measured along the plane of the tread nosing. Accessible means of egress must be provided in accordance with Section 1007.
A mezzanine must remain open to the room in which it is located, except for walls that are no higher than 42 inches. However, there are exceptions to this openness requirement. For instance, if the mezzanine accommodates ten or fewer people, or if there are two or more exits, the openness rule may not apply.
OSHA‘s regulations for mezzanines are covered under the construction standards for fall protection, specifically the Walking Working Surfaces Rule, 1910 Subpart D:
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