Building codes are sets of regulations governing the design, construction, alteration, and maintenance of structures. They specify the minimum requirements to adequately safeguard the health, safety, and welfare of building occupants.
Rather than create and maintain their own codes, most states and local jurisdictions adopt the model building codes maintained by the International Code Council (ICC). The ICC’s family of International Codes includes:
• International Building Code (IBC): Applies to almost all types of new buildings
• International Residential Code (IRC): Applies to new one- and two-family dwellings and townhouses of not more than three stories in height
• International Existing Building Code (IEBC): Applies to the alteration, repair, addition, or change in occupancy of existing structures. The ICC publishes new editions of the International Codes every three years and many states and localities have adopted them since the first editions were issued in 2000. In 2000, the three regional model code organizations (BOCA National Code, SBCCI Standard Code, and ICBO Uniform Code) combined together to form the ICC.
What Are Seismic Codes?
Some provisions within the IBC, IRC, and IEBC are intended to ensure that structures can adequately resist seismic forces during earthquakes. These seismic provisions represent the best available guidance on how structures should be designed and constructed to limit seismic risk.
Changes or additions to the seismic provisions come from many different sources, including new research results and documentation of performance in past earthquakes. A primary resource is the 2020 NEHRP Provisions Edition Volume I and Volume II. FEMA’s companion document Earthquake Resistant Design Concepts (FEMA P-749) provides a nontechnical background explanation.
Adoption of the model codes is uneven across and within states, even in areas with high levels of seismic hazard. Some states and local jurisdictions have adopted the codes but have made amendments or exclusions relating to the seismic provisions.
Other jurisdictions have been slow to adopt the latest code editions. Unless your community has adopted the latest model building code—including its seismic provisions—new structures in your community will probably not provide the current minimum level of protection from earthquake hazards to you and others who use them.
How Are the Codes Enforced?
Adopting the latest building codes is only part of the solution. Codes must also be effectively enforced to ensure that buildings and their occupants benefit from advances in seismic provisions in the model codes. For the most part, code enforcement is the responsibility of local government building officials who review design plans, inspect construction work, and issue building and occupancy permits.
What About Older Buildings?
Except in certain circumstances, such as when a building is significantly renovated or altered or there is a change in its use that triggers the IBC or IEBC, the code requirements for existing buildings are those that were in effect when the structure was designed and constructed.
Your community probably has many older structures that are not protected against earthquakes. This is because buildings are often used for decades before being replaced or substantially altered.
These existing buildings are the single biggest contributor to seismic risk in the United States today.