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Understanding Building Codes

Illustration is a map showing the route of technical results becoming updated standards, updated model codes, and then local laws.
Credit: N. Hanacek/NIST

Over the last century, building codes and standards in the U.S. have been improved to better protect people from harm. But what triggered these updates? And how are decisions made about what to change? 

The short answer: When buildings fail to keep their occupants safe or even come close to failing during a catastrophic event — natural, human-caused or a mix of both — organizations step up to study what caused the failure. Then, government and industry organizations take action through established processes to etch those lessons into codes.  

As an agency that has studied and investigated building failures for more than 50 years and wields legislative authority to get to the bottom of disasters, NIST plays a key role in updating codes. In addition to calling for enhanced codes and standards based on technical findings, NIST experts, along with many others, work to turn these recommendations into actionable codes.  

What Is a Building Code, Exactly? 

Building codes are laws that set minimum requirements for how structural systems, plumbing, heating, ventilation and air conditioning (HVAC), natural gas systems and other aspects of residential and commercial buildings should be designed and constructed. In the U.S., building codes mostly fall under the purview of state and local governments. 

Lawmakers and government officials in most jurisdictions do not build their codes from scratch. Instead, they start with common draft language — called a model code — the requirements of which they may tighten or loosen, tailoring the code to their state, county or city’s needs. 

Model codes aim to safeguard occupants from dangerous conditions by specifying fire safety and evacuation requirements as well as the level of wind, rain, hail or other hazards that buildings should withstand. These codes, produced primarily by the nonprofit International Code Council (ICC), incorporate existing consensus building standards developed by professional organizations with expertise in a particular relevant field. 

The standards specify design practices associated with a diverse array of building elements including sprinklers, exit signage, structural steel and concrete, windows and many more. ASTM International, the National Fire Protection Association (NFPA) and the American Society of Civil Engineers (ASCE) are just some of the many standards organizations commonly referenced in the model codes. 

As gaps or errors are identified and as pertinent information about engineering, natural hazards or human behavior comes to light, standards organizations and the ICC can upgrade standards and model codes through a process that normally takes many years.  

How Are Building Standards Created and Updated?

The principal building blocks of model codes are standards, so a natural starting point for altering a code is to update the appropriate standard first. Committees within standards organizations that produce consensus standards follow guidelines defined by the American National Standards Institute (ANSI)

These guidelines call for balanced committee representation among interested parties — builders, manufacturers, building officials, researchers and others — so that one group does not dominate the process. NIST researchers frequently participate on these committees, often leading the charge on specific updates based on their investigatory and research findings.  

New versions of standards are published on a regular schedule, generally every three to six years, and are developed by committees of dozens or sometimes hundreds of volunteer experts. 

Following the publication of a standard, the clock starts ticking for the next update. The associated committee will put out a call for proposed changes for the next version. Any member of the public or the committee can put forth a proposal to alter a standard. Then, once the call closes, the committee deliberates and votes on the proposals. 

ANSI also requires a public review period on new editions of standards, so a committee will issue draft standards for public comment after it votes on the proposals. The committee must address all comments from the public either by providing a technical explanation or agreeing to a modification. If there’s not enough time to address a question or update, it can be tabled for the next edition.

Building standards committees generally write standards with the intent that they become a component of a model code. This is because, although state and local governments could reference a standard directly, they are more likely to use a model code, which arranges many essential standards in one place, in a way that streamlines the design process for industry.  

How Are Model Building Codes Updated?

The ICC’s model codes, which include separate codes for residences and for new and existing commercial buildings, are developed and updated every three years. 

Similar to standards development, there is a period of time when anyone can submit proposals to change a code. Afterward, committees of about a dozen volunteer experts selected by the ICC vote on proposals for the model code at public hearings where anyone can provide testimony either for or against a proposal. Although the ICC does not strictly follow ANSI’s guidelines, the organization expresses that it aims to fairly represent different interests on its model code committees.

NIST experts who strive to incorporate the latest science into building standards often also make their case through testimony at these hearings. A new edition of a consensus standard can provide a basis for a proposal to update a building code but does not guarantee success. Committees may motion to approve a proposal as is, accept it with some modifications or vote to disapprove. However, the committee vote is not the last word. 

Following a public comment period, a second public hearing takes place to resolve all comments. Here, voting opens up to a much larger pool of ICC governmental members who are physically present at the hearing or who select to vote remotely. This group, largely composed of building officials from around the country who use model codes, votes on how to respond to public comments, providing the final word on what will be included in the next edition of a model code. 

Publication typically comes a year later. 

How a (Model) Code Becomes a Law

The long road ends when state and local lawmakers adopt these model codes into the law of the land that inspectors will use to judge the safety of buildings. 

Building codes vary from state to state and between jurisdictions. While California’s codes focus more on earthquakes, Florida’s include more measures addressing hurricanes. Some states may limit or strike out new requirements they view as too costly, unnecessary or otherwise inappropriate for their constituents. Others may see value in the updates, sealing them into law or even strengthening them to protect their community.

Created June 16, 2022, Updated June 21, 2022