April 13, 2017

Building A Storm Shelter to ICC-500 Requirements

The need for storm shelters is greater than ever as the 2017 tornado season kicks off to a powerful start. As of March 21, 2017, there have been 367 reported tornadoes and, as of April 4, there have been 26 deaths due to tornadoes in the United States. That is more tornadoes than the combined total during the months of January, February and March in 2014, 2015, and 2016 of 313. It also makes January 2017 the second-deadliest month on record due to tornadoes. The majority of people who have died in 2017, lived in mobile homes and houses; without the safety of a storm shelter.

The ICC-500 Design and Construction of Storm Shelters

In 2003 the International Code Council (ICC) and the National Storm Shelter Association (NSSA) began working together to develop a national consensus standard for storm shelters. It was named the ICC/NSSA Standard for Design and Construction of Storm Shelters (ICC-500). The FEMA P-361 served as the framework for the development of the ICC-500 and the standards for the ICC-500 are accredited by the American National Standards Institute (ANSI)The purpose of the ICC-500 was to provide design standards for a storm shelter that would ensure the safety of those in a building from storms that produce high winds and flying debris. The first publication of the ICC-500 occurred the summer of 2008. Since 2009, the International Building Code (IBC, Section 423) and International Residential Code (IRC, Section R323) have utilized ICC-500 as their reference standard6 and require building storm shelters according to ICC-500. The ICC-500 provides builders, engineers, architects, etc. a guide for occupancy safety requirements along with wind speed and debris impact resistance for storm shelters.

The 2014 International Code Council’s (ICC) ICC-500 is the most current ICC/NSSA standards for construction and design and construction of residential and community storm shelters. There are several basic criteria to the 2014 ICC-500.

  • The standard is intended for use by government agencies and organizations along with model codes to achieve consistency in the design and construction of storm shelters
  • ICC-500 covers the design, construction, installation, and inspection of both community and residential storm shelters
  • Residential storm shelters have a capacity not to exceed 16 people
  • Community storm shelters are not residential storm shelters
  • Storm shelters can be separate, detached buildings, or enclosed or partially enclosed within a host building
  • The 2015 edition of the IBC-Section 423 requires that if the following types of buildings, located in a 250 mph wind speed zone, the buildings must include a storm shelter as specified and in accordance with the ICC-500  Figure 304.2(1).
  1. K-12 school buildings with a capacity of 50 or more occupants, with certain exception
  2. Emergency operations centers
  3. Fire, rescue, and ambulance stations  
  4. Police stations
  5. 911 call stations

The ICC-500 Requirements for Building a Storm Shelter

The ICC-500’s design of a storm shelter far exceeds the wind load and performance requirements of a regular building code. A shelter's envelope must withstand wind-borne debris, the collapse of the adjacent structures, falling objects, etc.  A shelter must have a strong continuous load path that resists overturning, uplift, and foundation connection failure. Storm shelters in areas specified by the ICC-500 Figure 304.2(1) must meet the requirements of both the 2015 IBC and the ICC-500. These requirements apply to shelters that are separate, detached buildings or constructed as safe rooms within a building. Here is a list of the requirements for a storm shelter as specified by ICC-500:

  • Storm shelters must be large enough to accommodate all the occupants of the building
  • The location of the storm shelters must be within the buildings they serve or located no more than 1000 feet from at least one exterior door of the building
  • The 2015 IBC requires exit doors in the envelope of the storm shelter. The number of exit doors is dependent on the number of occupants. Each exit door must have an emergency escape
  • The storm shelters must provide a minimum level of natural or mechanical ventilation and lighting
  • Toilets and hand wash systems have to be independent of city systems
  • The entire envelope of the storm shelter must meet the structural criteria of ICC- 500. The design of the shelter must resist a 250 mph design wind speed, and resist the impact and cyclical pressure in accordance with ASTM E1886/ E1996. Also, the walls of the safe room must withstand a debris missile impact of a 15-pound 2-inch X 4-inch shot at 100 mph and the roofs must withstand an impact of a 15-pound 2-inch X 4-inch shot at 67 mph

Bautex™ Block Wall Assembly Exceeds ICC-500 Requirements for Storm Shelter Design

Bautex Block Wall Assembly’s concrete grid and continuous wall system meet the Federal Emergency Management Agency FEMA 320 and FEMA 361 guidelines in storm zones with possible wind speeds up to 250 miles per hour. The Bautex Block single integrated concrete assembly also meets or exceeds the following ICC-500 and FEMA standards for debris impact.

  • Series 1 FEMA 320/361 Bautex Block Panel with Brick Veneer.
  • Series 2 FEMA 320/361 Bautex Block Panel with CMU Block Veneer.
  • Test projectile 15 lb. wooden 2-inch X 4-inch propelled at 100 mph.

Buildings in regions with 250 mph wind speeds for tornadoes must include a storm shelter in their design. Design and construction of the storm shelters must meet the requirements of both the 2015 IBC and the ICC-500. An ideal choice for material for building a storm shelter is the Bautex Block Wall Assembly.  It meets all requirements for wind speed and impact resistance. In addition the Bautex Block is insulated, fire resistant and has above-grade moisture protection.

The International Code Council (ICC) is a non-profit, membership association dedicated to the development of a single set of comprehensive and coordinated national modela construction codes (I-Codes). The International Code Council (ICC) has three Family of Companies.

  • The ICC Evaluation Service (ICC-ES) evaluates building products for compliance with I-Codes
  • The Solar Rating & Certification Corporation (SRCC) provides authoritative performance ratings, certifications, and standards for renewable energy products
  • The International Accreditation Service (IAS) provides objective evidence that calibration laboratories, inspection agencies, building departments, fabricator inspection programs and IBC special inspection agencies.

Model construction codes are developed and maintained by a standards organization (like the ICC) which is independent of the company or government institution that is responsible for imposing the building code on a construction project.

Local and State governments use I-Codes to design, build and compliance process to construct safe, sustainable, affordable and resilient structures. Government agencies depend on the ICC model I-Codes because of the complexity and cost of developing building codes and standards. Currently, fifty states and the District of Columbia have adopted the ICC model I-Codes; altering them to fit specific local construction practices, climate, and geography. 

The National Storm Shelter Association (NSSA began in 2000, in Lubbock, Texas. The National Storm Shelter Association initial purpose was to recognize and give distinction to storm shelter producers and products who meet high standards of quality. The first major task of the NSSA was to determine these high industry standards for storm shelters. The National Storm Shelter Association (NSSA) worked alone to develop codes until 2002. In 2002 an agreement was reached between NSSA and ICC to develop a national consensus standard for storm shelters. Accreditation of the standards is by the American National Standards Institute (ANSI). The ICC/NSSA Standard for Design and Construction of Storm Shelters is named the International Code Council-500  (ICC-500).

FEMA P-361 - Safe Rooms for Tornadoes and Hurricanes -  was first published in 2000 and is intended for architects, engineers, building officials, local officials and emergency managers, and prospective safe room owners and operators. It guides the planning, design, construction, and operation of residential and community safe rooms that will protect people during extreme wind events. The FEMA P-361 is intended for those seeking more technical guidance than FEMA P-320 provides.

The 2015 International Building Code  (IBC) is administered by the ICC and contains commercial construction regulations. The International Residential Code (IRC) is administered by the ICC and contains residential construction and remodeling regulations. The IRC is used or adopted in 49 states, Guam, the District of Columbia, Puerto Rico and the U.S. Virgin Islands. The IBC is used or adopted in 50 states, the District of Columbia, Guam, Northern Marianas Islands, New York City, Puerto Rico and the U.S. Virgin Islands. The IBC and IRC are model building codes that communities can adopt in whole or adapt to fit the local construction practices, climate, and geography. Only If the IBC or IRC are adopted whole, they become legal in a community. The IRC and IBC are designed to provide building safeguards to public health, safety, and welfare. The codes intend to protect public health and safety while avoiding both unnecessary costs and preferential treatment of particular materials or methods of construction. The 2015 IBC and IRC are fully compatible with all other published ICC codes.

The ICC referenced standard is an industry agreement of the level of performance in the designing manufacturing, testing and installing of materials, products or assemblies.  A referenced standard is a referenced reliable resource. It is not a primary law; like a model code. A model code becomes law when adopted by a jurisdiction. A standard becomes law when referenced in a model code.  Referenced standards are an extension of the code requirements and are therefore equally enforceable.

2015 IBC - Section 423.4 - Storm Shelters. Schools with 50 or more people and where shelter design wind speeds are 250 mph, as specified by Figure 304.2(1) of ICC 500 must have a storm shelter (safe room). The shelter must be large enough for everyone in the school.

FEMA P-320 -  Taking Shelter from the Storm - was first published in 1998 and is meant for builders, contractors, and homeowners for decision-making guidance on tornado and hurricane safe rooms.  The FEMA P-320 also has specific requirements for a safe room, which use ICC 500 as a referenced standard, however, are considered slightly more conservative.   

  • Safe rooms must be anchored to the building's foundation to resist overturning and uplift
  • A safe room must have a continuous load path that resists lateral and uplift loads during high winds.
  • The roof, openings, and walls of a safe room must resist perforation by windborne debris.
  • The walls of the safe room are independent of the rest of the building.