Tornadoes occur in the United States more frequently than any other country. According to the National Weather Service, approximately 1,000 tornadoes happen across the country annually, resulting in an average of 1,500 injuries and 80 deaths. In 2011, the seventh deadliest tornado in American history occurred in Joplin, Missouri, taking the lives of 158 people.

Although the smallest tornado path widths are less than 10 yards, the largest widths can exceed one mile. However, a tornado's size is not necessarily indicative of its intensity. Even smaller-sized tornadoes have caused significant damage on paths that lasted longer than 100 miles. 

Some studies show that there could be a potential connection between climate change and tornado frequency in the future, including tornadoes occurring in more vulnerable areas. To promote life safety during these unfortunate events, the Federal Emergency Management Agency (FEMA) created FEMA P-361, and the International Code Council (ICC) developed ICC 500 with guidance and requirements.

Timeline for FEMA and ICC guidelines and building codes

The following shows a timeline of the standard and building code development process over the past several decades:

• 2000: FEMA released the first edition of FEMA P-361, outlining the criteria of safe rooms for tornadoes. Before this release, no guidelines existed for safe room design or construction. 
• 2002: The National Storm Shelter Association (NSSA) collaborated with the Southern Building Code Congress International, Inc. (SBCCI) of the ICC, developing a national consensus standard for safe rooms and storm shelters. This revolutionary collaboration eventually developed into ICC 500. 
• 2008: FEMA published the second edition of FEMA P-361. In addition, the ICC released the first official version of ICC 500, providing the minimum requirements to safeguard public health relative to the construction of storm shelters.
• 2009: The International Residential Code (IRC) and the International Building Code (IBC) adopted ICC 500 as the governing standards for storm shelter design and construction.
• 2015: FEMA published the third edition of FEMA P-361, providing design and construction guidelines for shelter occupants with near-absolute protection from winds and wind-borne debris. Additionally, the IBC released its 2015 edition.
• 2016: FEMA revised OMB Circular A-119, which details the national strategy for creating standards.
• 2018: FEMA created several sections of the Disaster Recovery Reform Act (DRRA) to amend the Stafford Act, including enforcement policies of the latest published editions of relevant consensus-based standards, specifications, and codes.
• 2021: The ICC released the 2021 International Building Code.
• 2022: FEMA published its building codes strategy, which acts as the blueprint for managing and advancing building code efforts to help people before, during, and after disasters.

What is FEMA P-361?

FEMA created FEMA P-361 to provide guidelines for designing, constructing, and operating safe rooms that protect occupants during severe weather events, including tornadoes and hurricanes. The initial release was critical because it offered best-practice recommendations to ensure effectiveness in providing life-saving protection. It covered various aspects of shelter design, including structural integrity, window and door security, emergency communication, and ventilation. 

FEMA P-361 exists to provide best-practice guidance related to designing, constructing, and operating safe rooms. It outlines the criteria to build a shelter that protects against tornadoes and hurricanes. Because FEMA P-361 is a guideline and not a standard, it only provides recommendations. The only time it becomes a requirement is when a FEMA grant funds a storm shelter's design and construction. 

FEMA released its most recent update of this standard in 2021, which includes considerations from the 2020 consensus standard by the ICC and NSSA.

What is ICC 500?

The ICC developed the ICC 500 as a consensus standard using the first edition of FEMA P-361 as guidelines. It establishes construction and design requirements for storm shelters in municipalities or states adopting the 2015 IBC standard. 

ICC 500 outlines the minimum design, construction, and installation requirements to protect occupants from the potentially damaging effects of tornadoes and hurricanes. It ensures that storm shelters are capable of withstanding high winds, flying debris, and other hazards associated with these storms.

The IBC and IRC incorporated ICC 500 in 2009. The purpose was to regulate the design and construction of buildings and rooms designated as safe rooms or storm shelters.

FEMA P-361 vs. ICC 500

Several of the primary differences between FEMA P-361 and ICC 500 include:

• FEMA P-361 includes best-practice guidelines that use language like ”should" and “recommended.” FEMA P-361 safe rooms provide occupants with near-absolute protection.
• ICC 500 is an enforceable regulation that uses language like “shall" and “required.” ICC 500 storm shelters provide occupants with life safety. 

Another variation between the two is the wind-speed design requirements. FEMA P-361 requires a 250 mph wind speed design for all areas, while ICC 500 requirements can range from 130 mph to 250 mph, depending on the shelter's specific location.

Safe room requirements

Several factors determine the required codes for areas adopting the 2015 IBC or higher inside the 250 mph wind speed zone. Shelters must meet ICC 500 standards when building:

• K-12 school buildings with occupancy of 50 or more
• Fire, rescue, police, and ambulance stations
• 911 call stations
• Emergency operation centers  

Remember that code adoption will vary by the municipality within each state. It is also critical to know that the ICC 500 standards do not mandate a safe room for locations outside the 250 mph wind zone, as it states only that storm shelters must meet these standards if constructed.

If you build a safe room in any location and wish to participate in the FEMA grant funding program, you must abide by the more strict guidelines within FEMA P-361.

Funding

FEMA supports safe room initiatives through several grant programs. These programs aim to support communities in building new or modifying existing storm shelters to protect individuals during severe weather events like tornadoes.

FEMA funding for storm shelters typically operates through two primary grant programs — the Hazard Mitigation Assistance (HMA) program and the Public Assistance (PA) program.

The HMA program provides monetary grants to states, tribes, and local communities to build shelters that reduce the risk and impact of disasters. This program can help fund the construction of storm shelters in areas vulnerable to severe weather. In contrast, the PA program provides financial assistance to communities to repair, rebuild, or replace existing public infrastructure damaged by disasters.

State Hazard Mitigation Officers (SHMOs) can advise you on the information you need in order to secure funding for your project and any applicable local, state, or federal design requirements. Your SHMO will also be able to provide information about the various funding sources available.

Hurricanes

Because of a hurricane's rainfall and higher wind speeds, hurricane shelters and safe rooms fall under the ICC 500 standard with several additional regulations. Most significantly, the standard notes that most residents can leave areas facing immediate impact and seek safe refuge outside the at-risk area due to a hurricane's advanced notice. 

However, people like first responders and those physically unable to leave the area would remain in harm’s way. As a result, FEMA allocates grants designed for municipalities that cannot remove residents from harm's way during a hurricane. Other ICC 500 requirements for hurricane shelters include:

• Zones with wind speeds from 160 to 235 mph must follow ICC requirements for all hurricane storm shelters.
• ICC 500 requires structural design for rain loads according to ASCE 7. ICC 500 determines the rainfall rate by adding 6 inches per hour to the rainfall rate established on existing maps. 

How Cornell can help

Although many of these codes and guidelines apply to specific areas and conditions, ethics should also play a huge role in determining whether to construct a safe shelter.  Even if your location does not fall into a region requiring a storm shelter, it may be beneficial to add one if the slightest possibility of a storm hitting exists. Besides giving you peace of mind, these precautions will enhance the protection of the people occupying your building.

At Cornell, we test and certify our StormDefender® Safe Room Door to FEMA P-361, third edition and ICC 500-2014 code standards. These doors can fit into existing openings and remain hidden until you need them to provide protection. StormDefender Safe Room Doors have various innovative features customizable to your facility. StormDefender includes our award-winning AlarmGard operating system, which connects directly to your building's alarm system – deploying the doors when the alarm is triggered. 

Contact us for more information

To learn more about the benefits of StormDefender doors, contact us online today. Our team can also walk you through available FEMA grants for tornado-safe rooms or any other storm shelter challenges that you need to solve.