What is 2019 ICC G5 Guideline for the Safe Use of ISO Containers?
What is International Code Council (ICC)?
Introduction
Current Regulatory Environment
State Level
Local Level
Temporary vs. Permanent
Temporary Single Unit
Permanent Single Unit
Temporary Multi-Unit
Permanent Multi-Unit
Nonstructural Aspects of a Shipping Container Building Project
Use and Occupancy Classification
Type of Construction
Fire Protection System
Means of Egress
Interior Environment
Structural Design
Special Inspections and Tests
Soils and Foundations
Steel
Referenced Standards
Addressing the Interior of the Container and the Wood Floor
FAQ’s and Best Practices
Over 30 million ISO intermodal shipping containers are currently in service worldwide. Each one is manufactured in accordance with ISO specifications and maintained under the International Maritime Organization’s (IMO) Convention for Safe Containers.
Both new and previously used containers are increasingly being repurposed, fueling a global, multi-billion-dollar industry. Many of these containers are transformed into structures that fall under the International Residential Code (IRC) or the International Building Code (IBC). Their use as a building material varies greatly—ranging from full structural components to smaller architectural elements.
As the trend of converting shipping containers into buildings accelerates, many local and state regulatory bodies are working to catch up with appropriate codes and compliance measures. The ICC Guideline was developed to assist jurisdictions, as well as designers, builders, engineers, and property owners, in understanding how to properly design, evaluate, and approve shipping containers when used as part of a building structure.
What is 2019 ICC G5 Guideline for the Safe Use of ISO Containers?
The ICC G5-2019 Guideline for the Safe Use of ISO Intermodal Shipping Containers is a technical guidance document published by the International Code Council (ICC). Its purpose is to aid jurisdictions, owners, architects, builders, and engineers in assessing how ISO shipping containers (sometimes called “intermodal” containers) may be safely repurposed as buildings or building components.
Scope & Purpose
The guideline covers the repurposing of ISO containers (i.e. used for shipping) into permanent or semi‐permanent building elements (e.g. residential, commercial, accessory structures).
It is not a code in itself, but a reference document to assist in review, design, and regulation. Jurisdictions may adopt or reference it in local building codes.
Its aim is to provide technical clarity on structural, durability, safety, and other design considerations specific to containers used in building projects.
The guideline is a technical aid, not a mandatory standard. Authorities having jurisdiction might choose to adopt portions or refer to it when reviewing plans.
Because containers were originally designed for shipping loads, not as buildings, many modifications (e.g. cutting large openings) can significantly alter load paths. The guideline emphasizes caution and often additional reinforcement.
Local codes (structural, fire, energy, plumbing, etc.) still govern. The guideline helps bridge gaps but does not override local requirements.
The guideline may reference or complement other evaluation reports or acceptance criteria. For example, ICC published updates related to ICC-ES’s AC462 (which deals with evaluation of repurposed shipping containers) in relation to G5.
What is International Code Council (ICC)?
The International Code Council (ICC) is the organization responsible for creating and maintaining the model building codes that form the foundation of most building regulations in the United States—and that increasingly influence construction standards worldwide.
- Full Name: International Code Council (ICC)
- Founded: 1994 (through the merger of three regional code organizations: BOCA, ICBO, and SBCCI)
- Headquarters: Washington, D.C., USA
- Type: Nonprofit membership association
- Members: Building officials, architects, engineers, fire safety professionals, and construction industry representatives
Purpose
The ICC’s main mission is to develop a coordinated set of building safety codes—known as the International Codes (I-Codes)—to protect public health, safety, and welfare in the built environment.
These codes serve as model regulations that local, state, and national governments can adopt, adapt, or reference to create their own building laws.
The International Codes (I-Codes)
The I-Codes cover every aspect of construction and building safety, including:
- International Building Code (IBC) – general building design and construction
- International Residential Code (IRC) – one- and two-family dwellings
- International Plumbing Code (IPC)
- International Mechanical Code (IMC)
- International Fire Code (IFC)
- International Energy Conservation Code (IECC)
- International Existing Building Code (IEBC)
- International Green Construction Code (IgCC)
- International Property Maintenance Code (IPMC)
And others (there are more than a dozen specialized codes)
How the ICC Works
The ICC develops codes through an open, consensus-based process, where government officials and industry professionals propose, debate, and vote on code changes.
The codes are updated every three years (e.g., 2018, 2021, 2024 editions).
The ICC also offers training, certification, and evaluation services, such as:
ICC-ES (Evaluation Service): Issues technical reports verifying that innovative building materials and products comply with code requirements.
Guidelines like ICC G5-2019, which help interpret how unconventional materials (such as shipping containers) fit into existing codes.
Global Influence
Although the ICC is based in the U.S., its model codes are used or adapted by many countries around the world as benchmarks for building safety, energy efficiency, and sustainability.
Introduction
Today, more than thirty million intermodal shipping containers built under the International Organization for Standardization (ISO) are in service worldwide. These containers are manufactured in accordance with ISO specifications and maintained following the International Maritime Organization (IMO) standards outlined in the Convention for Safe Containers.
Both new and previously used containers are increasingly being repurposed, creating a multi-billion-dollar global industry. Many are adapted for uses governed by the International Residential Code (IRC) and the International Building Code (IBC). As a construction resource, containers are applied in a wide variety of ways—from serving as the main load-bearing framework to functioning as smaller structural or architectural components.
For builders, engineers, and developers, the appeal of containers lies in their wide availability, strength, durability, security, mobility, and the speed with which projects can be completed. Their modular design also allows them to be stacked efficiently. The concept of converting containers into habitable spaces has gained popularity among architects and environmentally conscious designers, who highlight benefits such as recycling, resource efficiency, and sustainability.
These factors have led to a diverse range of container-based projects and emerging market sectors, which generally fall into two main categories:
- Single-unit vs. multi-unit applications
- Temporary vs. permanent installations
While container reuse continues to grow due to its ecological and practical advantages, state and local authorities are still adapting to this evolving trend. Regulatory responses have been uneven, resulting in a patchwork of overlapping or inconsistent requirements.
Nevertheless, many architects, engineers, and builders have successfully demonstrated that container-based projects can meet the intent and safety goals of the model codes and can be approved by the authority having jurisdiction (AHJ).
Scope
As with other ICC Guidelines, this document is not a regulatory standard but an informational reference designed to assist the building industry, design professionals, and code officials. It provides guidance on the safe and compliant repurposing of shipping containers—whether used as standalone buildings, as part of larger structures, or as individual structural elements.
When jurisdictions receive proposals to use containers in construction, code officials often face challenges in determining what best serves their community’s interests. Beyond typical zoning considerations, they may lack clear permitting pathways and applicable standards specific to container-based structures.
This guideline offers recommendations and background information to help all involved parties—officials, designers, and builders—achieve a reasonable and consistent level of safety, public health, and welfare for occupants of buildings that incorporate shipping containers.
Current Regulatory Environment
To understand how shipping container repurposing is currently regulated, it is necessary to recognize the roles and interactions of the various national, state, and local authorities that oversee construction projects. Each level of government influences how such projects are reviewed, permitted, and approved.
The Modular Building Institute (MBI)—a nonprofit trade association representing manufacturers, builders, and fleet owners involved in relocatable and permanent modular construction—has taken an active role in this area. MBI has engaged with both state and local agencies to raise awareness about the regulatory processes governing the use of containers in building projects.
At the same time, MBI, code officials, and other stakeholders are collaborating to establish consistent national-level standards and requirements. These efforts aim to streamline approvals, promote uniformity across jurisdictions, and support the safe and efficient expansion of container-based construction in the future.
National Level
Even though current regulations for container-based construction are fragmented and lack nationwide consistency, the use of shipping containers as buildings or structural components continues to gain acceptance across many state and local jurisdictions.
At the national level, recognizing the need for clear, consistent, and enforceable code language, the International Code Council’s (ICC) Building Code Action Committee (BCAC) undertook efforts to develop specific provisions within the International Building Code (IBC). These provisions are intended to guide design professionals and code officials in the evaluation and approval of future container-based projects. The ICC updates and republishes its model codes, including the IBC, every three years to reflect ongoing developments in the building industry.
The BCAC’s first code change proposal related to containers was officially submitted in January 2018 as Proposal G151-18. It was included in the ICC’s formal code development hearings that took place in April 2018, where various proposed changes were reviewed and voted on. During this process, the IBC General Code Committee made minor revisions to the original G151 text.
After the initial hearings, stakeholders were given the opportunity to provide public comments on all proposals, including G151. The only comment on that proposal came from the BCAC itself, suggesting a few editorial improvements and small adjustments.
The revised proposal was then debated and voted on during the Public Comment Hearings (PCH) in October 2018, followed by the Online Governmental Consensus Vote (OGCV)—a national vote among eligible ICC members.
Based on the combined results of both the PCH and OGCV votes, Proposal G151, as modified through Public Comments 1 and 2, was approved for inclusion in the 2021 edition of the International Building Code (IBC).
State Level
Across the United States, the regulation of repurposed shipping containers used in building construction is typically handled through statewide modular building programs or by specific state agencies responsible for approving residential and commercial structures (see Appendix 1).
In many states, modified containers can be used in construction only after they have been evaluated in accordance with the ICC Evaluation Service’s (ICC-ES) Acceptance Criteria AC462, titled Structural Building Materials from Shipping Containers. This document establishes performance and safety requirements for containers used as structural building elements.
However, regulatory approaches vary widely:
- Some states prohibit the use of modified containers entirely.
- Others provide conditional allowances or exemptions, depending on the size, purpose, or location of the project.
- A few states restrict modifications to containers performed outside their jurisdiction.
Even among states with established oversight programs, there are differences in interpretation—particularly concerning how and when a container may be modified or integrated into a building or structure.
Below are examples of how specific states regulate or exempt the use of repurposed containers:
- California – Oversees modular and off-site fabricated container structures (whether produced in-state or out-of-state) through the Factory-Built Housing Program and Commercial Modular Program under the Department of Housing and Community Development (HCD). For modular school buildings, regulation falls under the Division of the State Architect (DSA).
- Georgia – Regulates all containers intended for residential, commercial, or industrial use, including temporary construction-site offices. The state is also considering a rule requiring that containers be manufactured within 48 months prior to their conversion for building use.
- Maryland – Exempts certain industrialized buildings from regulation if they measure no more than 8 feet wide and 40 feet long, and are used for business, storage, or mobile office purposes not open to the public. Oversight of other types falls under the Industrialized Building Program administered by the Department of Housing and Community Development.
- Massachusetts – Permits only new U.S.-made shipping containers under its state modular program, prohibiting the use of repurposed or previously used containers.
- Ohio – Regulates containers that are modified off-site and contain concealed structural components under the Board of Building Standards’ Industrialized Unit (IU) Program.
- Texas – Allows repurposed shipping containers to be used in construction if they comply with ICC-ES AC462, under the Industrialized Housing and Building Program.
In summary, while some states are developing comprehensive frameworks to integrate container-based construction safely, others remain cautious or restrictive. This variation underscores the need for national consistency to support the broader and more predictable adoption of shipping containers in building projects.
Local Level
At the local level, regulatory approaches to the use of shipping containers in construction differ widely across jurisdictions. Many local governments defer to their state’s building regulations or codes, while others adopt modified versions of national model codes (such as the International Codes) to better align with local priorities and community standards.
In addition to building codes, local zoning ordinances often play a major role. These ordinances may include design and aesthetic requirements that restrict certain materials or styles of construction—limitations that can make the use of containers costly or impractical in some areas.
Below are examples of local laws and policies that specifically regulate or provide guidance for the use of shipping containers under defined conditions:
- City of Anchorage, Alaska – Policy AG.19: Intermodal Shipping Containers, Anchorage Building Safety Division. Effective November 21, 2016.
- City of Long Beach, California – Cargo Containers Used as Storage in Industrial Zones (effective February 18, 2008) and Cargo Containers Adapted as a Building Material (effective November 27, 2012), issued by the Building and Safety Bureau.
- City of Los Angeles, California – Cargo Container Conversion to Building Modules, Department of Building and Safety. Effective June 2017.
- City of Louisville, Kentucky – Homeowner’s Permit Tool Box: A Check Guide to Permitting Your Shipping Container Project in Louisville Metro, issued by the Construction Review Department, Louisville Metro Government Center (no effective date listed).
- City of Portland, Oregon – Code Guide, Special Construction – IBC/3/#1 & IRC/1/#2, Bureau of Development Services. Effective January 29, 2013.
- City of San Diego, California – Cargo Containers Information Bulletin 149, Development Services Department. Effective October 2015.
- City of Tioga, Texas – Ordinance No. 295, Grayson County. Effective 2011.
- County of Grayson, Texas – Ordinance No. 295, applicable to the City of Tioga and surrounding areas. Effective 2011.
- County of Yakima, Washington – Ordinance Chapter 19.18: Cargo Containers, Shipping Containers, Trailers, Storage Units, Yakima County Public Services, Building & Fire Safety Division. Revised March 30, 2017.
In summary, local governments play a crucial role in shaping how container-based construction is permitted or restricted. However, because each jurisdiction establishes its own policies and zoning rules, the result is a highly varied regulatory landscape that can either encourage or limit the growth of container-based building projects.
Industry Segments
Shipping containers can be repurposed in a variety of ways, and each type of application presents different design, regulatory, and safety considerations. For instance, a single temporary container used as a ground-level office space has very different requirements from a group of interconnected containers forming part of a multi-unit, permanent structure.
Likewise, there is an important difference between containers that function as complete buildings—with enclosed plumbing, electrical, and mechanical systems—and those that serve mainly as structural or supporting components within a larger building.
To address these distinctions and ensure that regulations reflect the specific characteristics of each application, the industry recognizes four primary segments. These categories serve as a framework for the development of appropriate codes, standards, and compliance procedures for container-based construction.
Single-Unit vs. Multi-Unit
There is a clear distinction between a single modified container used as a temporary or relocatable structure and multiple containers that are combined or altered to serve as building materials for a larger, permanent facility.
Recognizing these differences, several states and local authorities have updated their model codes or administrative procedures to include specific exemptions or requirements depending on the size, configuration, and intended use of the container project.
For reference, Appendix 3 outlines a simplified structural design approach suitable for single, stand-alone containers, as well as guidance for multi-unit container systems that are more complex and therefore require comprehensive structural analysis. These provisions are incorporated into the 2021 edition of the International Building Code (IBC).
Temporary vs. Permanent
When assessing how a shipping container must comply with building codes, code officials typically refer to Section 108.1 of the International Building Code (IBC) to determine whether a structure is temporary or permanent. Section 108.1 allows officials to issue permits for temporary structures that are valid for up to 180 days, with possible extensions granted for demonstrated need. Any container not classified as temporary is generally treated as permanent.
Section 108.2 of the IBC specifies that temporary structures must meet building code requirements necessary to protect public health, safety, and welfare, but they are not required to fully comply with all code provisions. For instance, containers classified as temporary may not need a permanent foundation. By contrast, containers designated as permanent typically must comply fully with all applicable building code requirements.
The classification of containers as temporary or permanent can differ by state or local jurisdiction. For example:
The City of San Diego and the City of Long Beach allow exemptions for containers temporarily placed on a site during the construction of a building with a valid permit, or for containers used as equipment, storage, or props during permitted special events.
It is advisable for design professionals and property owners to consult early with code officials to confirm the intended classification of their containers.
Some states also provide automatic exemptions based on occupancy type or usage. For example, construction site offices that are not open to the general public are often exempt from full building code requirements under state modular building programs.
Temporary Single Unit
Examples: Ground-Level Offices, Construction Site Offices, Storage Units
A typical 8’ x 20’ container used as a Ground-Level Office (GLO) is designed to remain on-site temporarily, in line with IBC Section 108.1, which allows for a 180-day permit. The building official may grant extensions if there is a valid reason.
Permanent Single Unit
Examples: Industrial Workspaces, Equipment Enclosures, Security Access Points
As the structure’s envelope is a shipping container, some code requirements—such as the 2% roof slope—cannot always be met. Nevertheless, life safety and other critical building codes must still be observed.
Temporary Multi-Unit
Examples: Pop-up Retail Spaces, Trade Show Installations, Special Event Structures
Even though these facilities are temporary, they are often open to the public. Therefore, they cannot automatically be exempted from code requirements solely because of their temporary status.
Permanent Multi-Unit
Examples: Industrial Housing, Hotels, Multi-Family Residences, Public Gathering Facilities
Fortress Obetz, currently the largest container-based structure in the U.S., serves as a permanent stadium hosting lacrosse games and festivals, illustrating the scale and complexity possible with permanent multi-unit container projects.
Current Code Requirements
Under the 2018 edition of the IBC, shipping containers can be utilized as building components, provided they meet the alternative building material provisions in Section 104.11. Because approval procedures differ by location, developers and builders should consult local authorities to understand state and local regulations, as well as the technical documentation required for project review and permitting.
There are multiple methods that a design professional, builder, or property owner can use to demonstrate compliance with the applicable codes in a given jurisdiction. Likewise, code officials may reference other consensus standards or technical documents to determine which code requirements should apply when evaluating container-based projects.
When containers are submitted to the authority having jurisdiction (AHJ) for use as buildings, structures, or structural elements, it is important to understand the general review and approval process. Like any other building, containers must adhere to model codes, including—but not limited to:
- International Building Code (IBC)
- International Residential Code (IRC)
- International Fire Code (IFC)
- International Existing Building Code (IEBC)
…and other applicable standards. These codes cover areas such as structural integrity, means of egress, sanitation, lighting and ventilation, accessibility, energy efficiency, and life safety for both new and existing buildings.
The permitting process generally begins with construction documents prepared by a registered design professional (IBC Section 107.1). According to the IBC, construction documents are “written, graphic, and pictorial documents prepared or assembled to describe the design, location, and physical characteristics of the elements of a project necessary for obtaining a building permit.” For container projects, this typically includes dimensions, material properties of the steel frame and wood floor, and any other information required under Section 107 to verify compliance with code.
There are several approaches a design professional, builder, or owner can take to demonstrate code compliance. Regardless of the method, the container must comply with locally adopted building codes as well as all applicable federal, state, and local environmental regulations.
The following sections on structural and nonstructural topics highlight key design considerations to include in construction documents when seeking code approval for container-based projects.
Nonstructural Aspects of a Shipping Container Building Project
The International Codes also cover the nonstructural aspects of a building project.
For detached one- and two-family homes and townhouses up to three stories, the International Residential Code (IRC) applies. The IRC addresses all residential construction requirements, including means of egress, smoke and carbon monoxide detection, energy efficiency, fire protection, fire-resistant construction, room dimensions, and sanitation.
All other types of buildings generally fall under the International Building Code (IBC). In many cases, the nonstructural provisions in the IBC are similar to those in the IRC. Key nonstructural considerations in the IBC include:
- General Nonstructural Information
Construction documents should provide basic project details, such as:
- Project address and legal lot description
- Total floor area and type of construction
- Number of stories
- Use and occupancy
- Fire separation distances or setbacks to property lines or adjacent structures
- Lot size and dimensions
- Location of streets, alleys, and parking spaces
At a minimum, this information helps code officials determine applicable code requirements for containers.
- Use and Occupancy Classification
Chapter 3 of the IBC establishes use and occupancy classifications for buildings, including repurposed containers. Accurate classification is critical because it determines allowable height, floor area, number of stories, fire hazard level, fire protection requirements, and the design of the means of egress.
- Type of Construction
Chapter 6 of the IBC defines the construction type based on building height and area (as outlined in Chapter 5). Every structure, including container-based buildings, must be classified into one of five types of construction, ranging from Type I (highest fire-resistance, non-combustible) to Type V (lowest fire-resistance, combustible). The higher the construction type, the greater the allowable height, floor area, and number of stories for the container structure.
- Fire Protection System
Chapter 9 of the IBC specifies minimum requirements for active fire protection systems, which are generally determined by the occupancy type, height, and area of the building. These factors influence fire-fighting strategies and relative hazards associated with each occupancy.
- Means of Egress
Chapter 10 outlines criteria for the design of safe building exit systems, providing a means for timely evacuation of occupants. Both prescriptive and performance-based approaches are used to ensure a safe egress system for all types of occupancy.
- Interior Environment
Chapter 12 of the IBC defines minimum standards for interior environments in container structures. This includes:
- Minimum room dimensions
- Temperature, lighting, and ventilation requirements
- Limits on sound transmission through walls, floors, and ceilings
- Ventilation of underfloor spaces
- Guidelines for toilet and bathroom construction
These nonstructural requirements are essential to ensure that container-based buildings are safe, habitable, and compliant with current codes.
Structural Aspects of a Shipping Container Building Project
Both the IRC and IBC contain specific structural requirements that address environmental factors such as wind, seismic activity, and snow loads, depending on the project’s location and intended use. These codes also specify foundation design requirements and live load capacities for building systems based on the type of occupancy. Projects that incorporate shipping containers as structural elements must meet all applicable structural provisions. Appendix 3 offers a preview of what will be included in the 2021 IBC regarding intermodal shipping containers.
Regardless of the project type, designers face multiple challenges from both a regulatory and engineering standpoint. They must provide detailed documentation to demonstrate structural integrity, as well as fire and life safety compliance.
Once a container is modified, it is treated as a building material component. Similar to a roof or floor truss, the modified container must be engineered to perform under all relevant structural loads. This includes:
- The design of connections between containers or structural elements
- The impact on container walls from any openings or modifications
- All loads resulting from the intended building features and functional requirements
Proper structural engineering ensures that modified containers function safely and reliably as part of a building or structure.
- General Structural
Construction documents should provide basic structural details, including the size and location of load-bearing members within the container. Key elements such as floor levels, column spacing, and offsets should be clearly dimensioned. Steel members that carry structural loads must be identified and verified to meet the ordered steel grade according to standards referenced in IBC Chapter 35. If the material grade is uncertain or not easily verifiable through markings or test records, the AHJ may require testing as outlined in IBC Chapter 17 or other approved methods to determine the material’s properties, quality, and limitations. (See the discussion on container steel at the end of this section.)
- Structural Design
Chapter 16 of the IBC establishes the minimum structural load requirements for all buildings and structures, including containers. It covers design loads, risk category assignments, and approved design methodologies to ensure the safety of life and property. This chapter references numerous nationally recognized design standards that guide engineering practices.
- Special Inspections and Tests
Chapter 17 of the IBC outlines procedures for testing materials and assemblies, labeling components, and conducting special inspections of structural systems. It defines the standards for inspection, testing, and reporting to verify the quality and compliance of materials and structural assemblies.
- Soils and Foundations
Chapter 18 of the IBC provides requirements for geotechnical and structural considerations in designing and constructing foundation systems that support container loads. Registered design professionals must exercise care in planning and designing foundations, obtaining sufficient soil data, applying accepted engineering methods, and using sound technical judgment.
- Steel
Chapter 22 of the IBC sets forth requirements for designing the structural steel components of containers, including cold-formed steel, steel joists, and related elements. This chapter specifies the applicable design and construction standards necessary to ensure the strength and safety of steel structural members used in container-based construction.
One challenge facing the authority having jurisdiction (AHJ) is the limited information available on the material properties and specifications of container steel components. Since these steel elements act as structural load-bearing members, they must be properly identified and verified to conform to the specified steel grade in accordance with IBC Chapters 22 and 35, as well as any additional standards approved by the code official.
Many shipping containers are manufactured outside the United States and may not meet U.S. standards. As a result, investigating and confirming the material properties is essential for code officials to determine whether the container is suitable for structural use.
Steel of uncertain quality should undergo the testing procedures outlined in IBC Chapters 17 and 22, or other approved standards, to establish its strength, quality, and limitations. Any steel elements that cannot be clearly identified by markings or test records require testing to confirm their compliance with relevant standards.
The intended use of the containers—whether as part of a multi-unit assembly or as a single, stand-alone unit—can also influence the evaluation of material properties and the level of testing required.
Referenced Standards
The Convention for Safe Containers (CSC) is an international agreement established through the 1972 International Convention for Safe Containers. Countries that have ratified the CSC are called Contracting Parties, with the United States being one example. The CSC is managed by the governments of the Contracting Parties and an organization appointed by them, known as a Classification Society.
At the point of manufacture, the selected Classification Society inspects containers. After passing inspection, each container receives a unique CSC Safety Approval Number and is fitted with a CSC Safety Approval Placard (see section on CSC Safety Approval Placard). The container also carries the decal of the Classification Society.
While model building codes generally do not reference international treaties, authorities having jurisdiction (AHJs) may choose to rely on an “approved agency” as defined in IBC Section 104.4. According to Chapter 2 of the IBC, an approved agency is “an established and recognized organization regularly engaged in testing, inspection, or product certification, and approved by the building official.” This provision allows AHJs to accept the work of Classification Societies in verifying container compliance.
In the U.S., the American Bureau of Shipping (ABS) is one organization authorized to administer the CSC and the referenced standards. Approvals issued by a Contracting Party are recognized by other Contracting Parties, allowing containers to operate globally under a unified set of safety regulations.
ABS is part of the International Association of Classification Societies (IACS), a technical, non-governmental organization composed of twelve marine classification societies. Collectively, IACS member societies oversee standards covering more than 90% of the world’s cargo ship tonnage.
Marine classification establishes technical and engineering standards to ensure the safety of life, property, and the environment. These standards govern the design, construction, and life-cycle maintenance of ships, offshore units, and other marine-related structures. IACS serves as a forum for its members to research, discuss, and adopt technical criteria that promote enhanced maritime safety worldwide.
The CSC establishes international standards in two main areas:
- Design Type Approval: Ensures that new containers are designed and constructed to meet the dimensional and strength requirements specified by ISO standards.
- Safety Inspections: Ensures that containers are maintained in a safe condition throughout their operational use.
The ISO standards most relevant to containers include ISO 1496-1, ISO 6346, and ISO 668. These standards require that every container meets a strict set of criteria in order to receive approval from an authorized Classification Society.
Overview of Relevant ISO Standards
ISO 668 defines the dimensional requirements and tolerances for container construction, ensuring consistency in size and shape.
ISO 1496-1 specifies the static and dynamic test loads that containers must withstand during construction. The standard includes tests such as:
- Stacking – verifying strength under stacked loads
- Lifting from the four top corner fittings
- Lifting from the four bottom corner fittings
- Longitudinal restraint – testing container resistance to longitudinal forces
- End wall strength
- Side wall strength
- Roof strength
- Floor strength
- Transverse rigidity – resistance to sideways deformation
- Longitudinal rigidity – resistance to lengthwise deformation
- Lifting from forklift pockets
- Lifting from the base at grappler arm positions
- Weatherproofing – ensuring the container is resistant to environmental conditions
ISO 6346 governs the identification, coding, and markings of containers. This information is displayed on the CSC Safety Approval Placard to indicate compliance with international standards.
CSC Safety Approval Placard
Containers that have been manufactured, tested, and inspected to meet ISO standards by a Classification Society are marked with a CSC Safety Approval Placard on the rear door. Often referred to as a data plate by code officials, this placard provides important information about the container, including its identification number, inspection date, and verification details that confirm the container was maintained in a safe operational condition.
Information typically found on the placard includes:
- Manufacturer’s name or identification number
- Date of manufacture
- Safety approval number
- Container identification number
- Maximum operating gross weight (kg/lbs)
- Allowable stacking load for 1.8G (kg/lbs)
- Transverse racking test force (Newtons)
- Valid maintenance examination date
A code official can generally rely on the data plate to confirm that a container was built and inspected in accordance with ISO standards. Design professionals can also use this information to verify compliance with ISO 1496-1 testing requirements. This verification is valid as long as the official accepts that the data plate is current and applicable to that specific container.
If a container lacks a data plate, the code official must use alternative methods to determine the container’s quality and reliability, which can complicate approval. It is therefore recommended that designers, builders, and owners check for the presence of the original data plate before purchasing or acquiring a container for repurposing. Using a container without a data plate, or removing it, may result in rejection by the AHJ.
Once the container is accepted and modified, retaining the data plate is no longer required, as the original information may no longer apply to the modified structure.
Addressing the Interior of the Container and the Wood Floor
When repurposing shipping containers, questions often arise regarding their previous use and construction, particularly focusing on two main concerns:
- What cargo was previously transported in the container?
- Does the wood floor require evaluation before reuse?
Containers used for cargo transport are subject to strict regulations to ensure safe packing, securing, storing, and separation of hazardous materials. They are inspected at loading and unloading points and when returned to depots for repair or storage. This makes it highly unlikely that a contaminated container would enter the marketplace.
Containers that receive a “cargo-worthy” designation during inspection have been verified to comply with standards set by the International Maritime Organization (IMO), the International Organization for Standardization (ISO), the International Maritime Dangerous Goods (IMDG) Code, and the Convention for Safe Containers (CSC). In the United States, many of these regulations are enforced under Title 49 of the Code of Federal Regulations by the U.S. Coast Guard.
Additionally, many state modular or industrialized building programs require manufacturers to maintain a quality control/quality assurance (QC/QA) program. Third-party inspection or QA agencies evaluate the manufacturer’s processes to ensure compliance with these programs, including procedures to mitigate contamination risks.
As with any repurposed material, a container should be thoroughly cleaned and sanitized before reuse. Depending on the intended application, it may also be appropriate to recoat the interior with a sealant or paint suitable for the planned use.
The Floor
Containers are manufactured with a wood platform floor. Because containers are exposed to various environmental conditions during transport and storage, these floors are typically made of marine-grade lumber that is treated to resist decay, moisture damage, and insect infestation. The presence of wood treatment chemicals may influence how the container is reused.
When evaluating the floor, the future intended use of the container should be considered. For example:
If the container will serve a static purpose with limited interior access—such as a storage unit or equipment shed—the existing floor can usually remain in place, as the container is effectively continuing its function similar to shipping.
This approach may also be suitable for containers used for short-term temporary purposes or permanent applications where there is minimal direct contact with the floor.
If there are concerns about the floor but it is determined to remain in the container, there are multiple options to address these issues, as discussed in the following sections.
One approach is to use the existing container floor as a subfloor and install an additional floor covering on top. Alternatively, if the flooring is in good condition, it can be sealed. In either case, direct contact with the treated wood is minimized, either by covering it with another material or by applying a protective sealant such as polyurethane.
During renovation, removal, or repair, special care should be taken to avoid inhaling dust from treated wood, especially if sanding is involved. Use of appropriate personal protective equipment (PPE), as required by local or federal regulations, is recommended. After any renovation or removal work, all surfaces should be thoroughly cleaned to remove dust and wood fragments and to prepare for the installation of additional flooring.
Another approach is to test the wood floor for treatment residues. For example, a study by the National Portable Storage Association (NPSA) examined four commonly used wood treatments for plywood flooring and concluded that the health risks from treated container floors are minimal to nonexistent. The full study can be obtained by contacting the NPSA (see Appendix 4 for details).
If the floor is to be retained, it should be inspected to confirm that both the floor and its supporting structure are in adequate condition and safe for the intended use. Any damaged or substandard flooring or structural members should be removed or replaced before reuse.
ICC-ES Acceptance Criteria for Shipping Container Building Materials (AC462)
ICC-ES is a nonprofit organization in the U.S. that evaluates new and innovative building materials, components, and systems. They issue Evaluation Reports (ESRs) that show a product meets building codes and technical standards. These reports rely on International Codes and sections 104.11 of the IBC and IRC, which let code officials approve materials or construction methods that aren’t specifically mentioned in the codes. This flexibility helps encourage innovation.
In February 2016, ICC-ES introduced AC462, which provides guidelines for reusing shipping containers as building materials. For any new building made wholly or partly from ISO containers, AC462 is a good starting point. It gives rules for demonstrating that containers meet code performance requirements, but it does not approve the finished building itself.
AC462 is regularly updated through a public review process, so the rules can change over time. It is important to know:
- AC462 is meant for new construction using containers, not for assessing existing buildings that have already been modified.
- While AC462 is a common and widely accepted method to show compliance, it is not the only way to determine if a container can be safely used in a building.
In short, AC462 helps designers and builders demonstrate that containers are safe as building materials, but final approval of the building itself is still up to the local code officials.
FAQ’s and Best Practices
Q: I own existing ground-level offices made from modified shipping containers. Can I keep using them?
A: It depends. If the structures were built to an earlier version of the building code or in line with a state modular/industrialized building program, they may be fine. Otherwise, they must meet the current code as enforced by the local Authority Having Jurisdiction (AHJ).
Q: Do I need to bring my existing container structure up to code if I move it to a new site?
A: Yes. The International Existing Building Code (IEBC) governs existing buildings. The 2018 IEBC defines an existing building as one built before the adoption of the relevant code or one with a legal building permit. Chapter 14 of the IEBC covers relocatable buildings, requiring them to meet site-specific requirements such as seismic, snow, and wind loads, and proper foundation support.
Q: Can I get an ICC-ES Evaluation Services Report (ESR) to show that my existing container can be used as a building?
A: Yes, but it must follow AC462 Acceptance Criteria. AC462 evaluates quality control processes for the steel components of the container, including their dimensions, chemical and physical properties, and confirms they meet code requirements for structural use.
Q: Do I have to get an ESR under AC462 to use containers as building materials?
A: No. AC462 is one method to verify the steel components, but other methods may be accepted if approved by the AHJ.
Q: How can I check for other chemicals or toxins from packing materials, cargo, or container construction?
A: The shipping container industry follows national and international safety protocols to minimize contamination risk:
- The International Maritime Dangerous Goods (IMDG) Code, developed by the International Maritime Organization (IMO), regulates the safe transport of hazardous materials by sea. It is internationally recognized and mandatory.
- In the U.S., the Environmental Protection Agency (EPA) regulates chemical imports under the Toxic Substances Control Act (TSCA). Importers must certify compliance, and U.S. Customs and Border Protection (CBP) will only release shipments with a valid TSCA statement.
In short, international and U.S. regulations already manage hazardous materials to ensure containers are safe for reuse.
Q: How high can containers be stacked?
A: Standard shipping containers are designed to carry up to 66,000 pounds of cargo and can be stacked up to nine units high for shipping purposes. When repurposed as buildings or structures, structural engineering and code compliance determine how high they can safely be stacked.
Q: How are existing relocatable building units being used?
A: There are roughly 350,000 relocatable building units currently owned or leased by the modular construction industry. These units are commonly used as construction site offices, security offices, and classrooms. About 15–20% of these units are modified shipping containers, though this does not include units owned by construction companies, schools, or private businesses. This percentage is expected to grow as older wood-framed units are retired and replaced with container-based units.
Q: How are container-based structures classified in terms of construction type?
A: Typically, container-based structures are classified as Type VB construction. However, with proper modifications, they can meet the requirements for other construction types. See IBC Chapter 6 for more details.
Q: Can container-based structures be used for any type of occupancy?
A: Yes. Container-based structures can be used for any occupancy or purpose, as long as all applicable code requirements for that particular use are met.
Q: What is the fire-resistance rating of shipping container walls?
A: There is currently no definitive study or testing that establishes fire-resistance ratings for container walls, roofs, or floors. Determining a fire-resistance rating may require performance testing or another method approved by the AHJ. The code references ASTM E119 as the standard for fire-resistance testing.
Link https://codes.iccsafe.org/content/ICCG52019