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Shelter from the storm: a history of design standards for storm shelters

Tuesday, July 18, 2017

Ken Kilzer, Facilities Industry Expert


It’s funny, but true; those of us living and working in Tornado Alley are more likely to run outside and look to the sky when the storm sirens blow than seek shelter in the basement. We realize that the odds of any one spot getting struck by a tornado are exceedingly small.

But, when that tornado is bearing down, the sane among us run to the closest perceived place of safety: a building. The especially fortunate of us will hunker down in a storm shelter within that building, a shelter designed by a professional architect and/or engineer.

As building designers in the Midwest, it is incumbent upon us to understand where storm shelter design requirements come from, what the current code requires, and how to apply these requirements in the “real world.”

It is much easier for a designer to correctly apply code requirements when he or she is familiar with the process that went into developing the requirements. This article presents background information regarding the development of the current storm shelter design requirements.

         Courtesy: (L) FEMA, (R) Romaine McDaniel and Safe Sheds, Inc.









The Federal Emergency Management Agency (FEMA) began work in the 1970’s to determine safe room design parameters by studying post-disaster damage and assessing building performance after tornados of national significance in the United States.

Since 1980, FEMA has provided technical guidance on tornado protection, beginning with the publication of TR-82A “Interim Guidelines for Building Occupant Protection from Tornadoes and Extreme Winds.”

Since this first publication, FEMA has continued to do research and analysis of post-storm damage and has issued updated design guidance culminating in the most recent publications, FEMA P-361 Safe Rooms for Tornadoes and Hurricanes: Guidance for Community and Residential Safe Rooms, Third Edition (2015), and FEMA P-320 – Taking Shelter from the Storm: Building a Safe Room for Your Home or Small Business, Fourth Edition (2014).










These publications are not Codes or Standards. They were not written with the intent of being included in building codes, but rather to provide basic research and design information to the public. In practice, however, they have been adopted into many municipal and building codes because of the absence of an official Standard.


In 2008, the International Code Council (ICC) along with the National Storm Shelter Association (NSSA), first published ICC 500-08 ICC/NSSA Standard for the Design and Construction of Storm Shelters. The difference between this standard and the previous FEMA publications was that this standard was produced in an open-ballot, consensus manner as required for legal code adoption. An updated version of ICC 500 was published in 2014. A commentary for the ICC 500-14 was published in February 2016.  

Although similar, the design recommendations of the FEMA documents are slightly more conservative than those of the ICC 500.











The ICC 500 was first referenced in Section 423 of the 2009 IBC as the standard to use when a storm shelter is planned. This reference was repeated in the 2012 IBC. Although the ICC 500 was referenced in these code editions, the application of the standard was not mandatory (unless added by a local code amendment). 

This changed with the publication of IBC 2015. Barring local amendments, IBC 2015 Section 423.1 now requires storm shelters for certain building occupancies in areas of the US where the shelter design wind speeds for tornadoes is 250 mph per Fig 304.2(1).


Obviously, local governing bodies are free to amend the IBC however they see fit, including the section on storm shelters. 

Designers should be aware that ICC 500 sets forth requirements for a range of topics related to the design and construction of storm shelters, including administrative items, structural design criteria, siting requirements, occupancy and egress requirements, essential features, and test methods for impact and pressure testing. 

Independent peer reviews and signed/sealed reports are required for certain community storm shelters. Special inspections are required for post-installed anchors and foundation elements. Additional design information, such as calculations for the number of sanitation facilities, minimum foundation capacity requirements, etc. is required to be included with the construction documents.

Before designing a storm shelter, it is important for designers to research the local code requirements, the appropriate design guide or standard, and the required level of quality assurances and quality control. There are significant differences between the FEMA documents and the ICC 500 standards, and even between the editions of the ICC 500 standards themselves. It’s best to confirm these requirements with the authority who has jurisdiction in the area. This will avoid costly mistakes.

If you have any questions, call me at 402.970.2304 or email me, kkilzer@olssonassociates.com.  ____________________________________________________________________________________________

ICC 500-08 Cover: Excerpted from the ICC 500-2008 ICC/NSSA Standard for the Design of Construction of Storm Shelters; Copyright 2008. Washington, D.C.: International Code Council

ICC 500-14 Cover and Figure 304.2(1): Excerpted from the ICC 500-2014 ICC/NSSA Standard for the Design of Construction of Storm Shelters; Copyright 2014. Washington, D.C.: International Code Council.
Reproduced with permission. All rights reserved. www.ICCSAFE.org

Ken Kilzer, PE

Civil Engineer

Ken has nearly 30 years of experience in the structural design of many building types, including commercial, retail, educational, military, and religious. Projects have ranged from small bank additions to large retail shopping malls. Recent military and government projects have included experience in structural hardening design per Anti-Terrorism/Force Protection requirements.  

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