Significant Changes to the IBC 2015 Edition 423.4 ■ Storm Shelters Serving Group E Occupancies 47

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CHANGE TYPE: Addition

CHANGE SUMMARY: Storm shelters are now required in Group E oc-cupancies located in those areas of the United States where the shelter design wind speed for tornadoes is at its highest.

2015 CODE: 423.4 Group E Occupancies. In areas where the shel-ter design wind speed for tornadoes is 250 MPH in accordance with Figure 304.2(1) of ICC 500, all Group E occupancies with an aggregate occupant load of 50 or more shall have a storm shelter constructed in ac-cordance with ICC 500. The shelter shall be capable of housing the total occupant load of the Group E occupancy.

Exceptions:

1. Group E day care facilities.

2. Group E occupancies accessory to places of religious worship.

3. Buildings meeting the requirements for shelter design in ICC 500.

CHANGE SIGNIFICANCE: In order to establish minimum requirements for structures and spaces designated as hurricane, tornado or combina-tion shelters, the IBC first referenced ICC 500, ICC/NSSA Standard for the Design and Construction of Storm Shelters, in the 2009 edition. However, in the 2009 and 2012 editions of the IBC, there are no scoping provisions to enact the technical requirements. Although the IBC did not mandate that storm shelters be provided, it did regulate their design if they were constructed. The 2015 IBC now provides scoping provisions that mandate the construction of complying storm shelters in specified Group E educa-tional occupancies.

423.4Storm Shelters Serving Group E Occupancies

School gymnasium constructed as tornado shelter

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48 PART 2 ■ Building Planning

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Due to unpredictable and often very short tornado warning time, there are many high-wind events where it is unfeasible to evacuate school buildings. Therefore, it is very important that refuge areas be provided that are capable of providing a near absolute level of protection for these vulnerable individuals. Section 423.4 now requires storm shelters in Group E occupancies located in those areas of the United States where the shelter design wind speed for tornadoes is at its highest. These areas, where the shelter design wind speed for tornadoes is 250 miles per hour, include a substantial portion of the central United States, as shown in Figure 304.2(1) of ICC 500.

In addition to the necessary administrative and application provi-sions established in Chapter 1 and the definitions provided in Chapter 2, the ICC 500 standard includes criteria for structural design, siting, occu-pancy, means of egress, access, accessibility, and fire safety. In addition, essential features and accessories are regulated independently for tornado shelters and hurricane shelters.

The IBC mandates that the shelter be designed to house the total oc-cupant load assigned to the Group E occupancy. As a general requirement, the provisions apply to all Group E occupancies having an occupant load of 50 or more. However, there are two types of educational occupancies where the construction of a storm shelter is not required. Group E day-care facilities are exempt, as are Group E occupancies accessory to places of religious worship. In addition, a separate storm shelter space is not re-quired where the entire Group E building is designed to meet the shelter requirements of ICC 500.

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