Overview of the ICC 500
ICC/NSSA Standard for the Design and Construction of Storm Shelters

Based on the 2015 International Codes^® 

Course description
•	The ICC 500 is a standard for the design and construction of storm shelters for protection from tornados and hurricanes.  This course will review where storm shelters are required by the International building codes.  There will also be an overview of the technical requirements, or the how to, requirements in the ICC 500. 
 
•	The needs of the type of shelter differ because of the differences between tornadoes and hurricanes.  Some of the biggest differences is the amount of warning time to get to a shelter, the time the occupants will stay in the shelter and the differences in the forces from the wind and debris on the shelter.  This class will explain those differences and the why behind the requirements.
Goal
…determine the minimum 
technical requirements for storm shelters in.
•	2015 IBC.
•	2015 IRC.
•	ICC 500-2014: Standard for the Design and Construction of Storm Shelters
Objectives 
•	Upon completion of this seminar, you will be better able to:
•	Identify where the ICC 500 is scoped in the codes
•	Determine the extent to which storm shelter standard provisions apply.
•	Identify scoping and technical requirements
Presentation organization
•	Title slides indicating topic/main code section

•	Performance requirements – Main ideas/ Philosophy

•	Code definitions or tables

•	Example

•	Quick questions on what we learned

Scoping
All referenced standards
IBC Section 102.4
•	Considered part of the code to the extent referenced
•	Conflicts – codes rule

IBC Definitions
[BS] STORM SHELTER. A building, structure or portions thereof, constructed in accordance with ICC 500 and designated for use during a severe wind storm event, such as a hurricane or tornado.
Community storm shelter. A storm shelter not defined as a “Residential storm shelter.”
Residential storm shelter. A storm shelter serving occupants of dwelling units and having an occupant load not exceeding 16 persons.
IBC
SECTION 423
STORM SHELTERS
2015 423.1 General. In addition to other applicable requirements in this code, storm shelters shall be constructed in accordance with ICC 500.

2018 423.2 Construction. In addition to other applicable requirements in this code, storm shelters shall be constructed in accordance with ICC 500. Buildings or structures that are also designated as emergency shelters shall also comply with Table 1604.5 as Risk Category IV structures.
IBC
2015 423.1.1 Scope. This section applies to the construction of storm shelters constructed as separate detached buildings or constructed as safe rooms within buildings for the purpose of providing safe refuge from storms that produce high winds, such as tornados and hurricanes. Such structures shall be designated to be hurricane shelters, tornado shelters, or combined hurricane and tornado shelters. 

2018 423.1 General. This section applies to the construction of storm shelters constructed as separate detached buildings or constructed as rooms or spaces within buildings for the purpose of providing protection from storms that produce high winds, such as tornadoes and hurricanes during the storm. Such structures shall be designated to be hurricane shelters, tornado shelters, or combined hurricane and tornado shelters. Design of facilities for use as emergency shelters after the storm are outside the scope of ICC 500 and shall comply with Table 1604.5 as a Risk Category IV Structure.
IBC
2015 423.3 Critical emergency operations. In areas where the shelter design wind speed for tornados in accordance with Figure 304.2(1) of ICC 500 is 250 MPH, 911 call stations, emergency operation centers and fire, rescue, ambulance and police stations shall have a storm shelter constructed in accordance with ICC 500.
Exception: Buildings meeting the requirements for shelter design in ICC 500.

2018  IBC has removed the exception as unnecessary.
IBC
423.4 Group E occupancies. In areas where the shelter design wind speed for tornados 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 accordance 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.

2018 IBC has created a separate section for capacity.  
2018 IEBC will require storm shelters in additions to schools.
IBC 
2018 423.4.1 Required occupant capacity. The required occupant capacity of the storm shelter shall include all of the buildings on the site and shall be the greater of the following:
1. The total occupant load of the classrooms, vocational rooms and offices in the Group E occupancy.
2. The occupant load of any indoor assembly space that is associated with the Group E occupancy.
Exceptions:
1. Where a new building is being added on an existing Group E site, and where the new building is not of sufficient size to accommodate the required occupant capacity of the storm shelter for all of the buildings on the site, the storm shelter shall at a minimum accommodate the required occupant capacity for the new building.
2. Where approved by the code official, the required occupant capacity of the shelter shall be permitted to be reduced by the occupant capacity of any existing storm shelters on the site.
IBC
2018 423.4.2 Location. Storm shelters shall be located within the buildings they serve or shall be located where the maximum distance of travel from not fewer than one exterior door of each building to a door of the shelter serving that building does not exceed 1,000 feet (305 m).
2018 IBC
TABLE 1604.5
RISK CATEGORY OF BUILDINGS AND OTHER STRUCTURES
Risk Category IV - Buildings and other structures designated as essential facilities, including but not limited to:
•	Designated earthquake, hurricane or other emergency shelters.

1604.10 Loads on storm shelters. Loads and load combinations on storm shelters shall be determined in accordance with ICC 500.
2018 IBC
1604.5.1 Multiple occupancies. Where a building or structure is occupied by two or more occupancies not included in the same risk category, it shall be assigned the  classification of the highest risk category corresponding to the various occupancies. Where buildings or structures have two or more portions that are structurally separated, each portion shall be separately classified. Where a separated portion of a building or structure provides required access to, required egress from or shares life safety components with another portion having a higher risk category, both portions shall be assigned to the higher risk category.
Exception: Where a storm shelter designed and constructed in accordance with ICC 500 is provided in a building, structure or portion thereof normally occupied for other purposes, the risk category for the normal occupancy of the building shall apply unless the storm shelter is a designated emergency shelter in accordance with Table 1604.5.
IRC
SECTION R323
STORM SHELTERS
R323.1 General. This section applies to storm shelters where constructed as separate detached buildings or where constructed as safe rooms within buildings for the purpose of providing refuge from storms that produce high winds, such as tornados and hurricanes. In addition to other applicable requirements in this code, storm shelters shall be constructed in accordance with ICC/NSSA-500.
2014 ICC 500
Application
•	The purpose of the Storm Shelter standard is to provide design and construction requirements for ‘safe rooms’ that provide refuge from hurricanes and tornadoes. 

History/Development
•	Started in 2002 as joint project for ICC and the National Storm Shelter Association (NSSA)
•	First edition in 2008
•	5 year cycle
•	Balances committee
•	Open consensus process
•	ICC has a commentary for this standard
Types of storms
Tornado
Hurricane
Hurricanes
•	A cyclonic wind circulation of the atmosphere around a low pressure center surrounded by strong winds and thunderstorms. 
•	Form over warm water near the equator.
•	Regionally know as hurricanes, typhoon or tropical cyclone
The Saffir-Simpson Hurricane Wind Scale 
Hurricane facts
Hurricanes:
•	Hundreds of miles wide.
•	Form only over warm ocean water.
•	Last for days and sometimes well over a week.
•	Produce rain and flooding in addition to powerful winds.
•	Independent, self sustaining storm systems. 
•	Winds ranging from 74 to about 200 mph
•	The hurricane season for the North Atlantic is June 1 through November 30.

Tornadoes
•	Storm systems that form on land due to pressure differences. 
•	Characterized by large rotating air columns, commonly shaped like funnels.
•	Can reach speeds over 300 mph before dissipating. 
•	Most tornado deaths are from flying debris. 

The Fujita Scale

Tornado facts
Tornadoes
•	Rarely over a mile wide
•	Usually form over land
•	Usually last minutes, rarely a few hours
•	Cause damage via wind and debris
•	Dependent on a large storm to develop and keep going 
•	Winds range from 65 to about 300 mph
•	Often have a condensation funnel.
•	The tornado season runs from later winter through mid summer, however, tornadoes can happen all year.
•	The strongest tornadoes have faster winds than the strongest hurricanes.

Types of shelters

•	Shelters used for hurricanes 
•	Shelters used for tornadoes
•	The primary difference in these two types is the expected duration of the storm.
•	Hurricane shelters – 24 hours
•	Tornado shelters – 2 hours 
Types of shelters
What requirements differ between hurricane and tornado shelters?
•	Occupant density
•	Sanitation
•	Water supply
•	Ventilation
•	Emergency power
•	Size/speed of flying debris

Types of shelters

Application and Administration
Chapter 1

Scope, applicability and provisions for compliance
•	For tornado and hurricane shelters
•	Can be a separate structure or within another building
•	Provides minimum requirements via alternative compliance paths
•	Construction not addressed should comply with IBC

Occupancy Section 104
•	Shelters used for other purposes shall be the IBC Group for those occupancies.
•	Dedicated facilities with >=50 occupants is Group A-3
•	Dedicated facilities with <50 occupants is Group B
Inspections, foundations, design loads
•	The code official will inspect.
•	Peer review
•	Special inspections/Observations
•	Construction drawings
•	Labeling (FEMA P-361)

Chapter 2
Definitions
Definitions
Same as IBC Definitions.

STORM SHELTER. A building, structure or portions thereof, constructed in accordance with this standard, designated for use during a severe wind storm event, such as a hurricane or tornado.
Community storm shelter. Any storm shelter not defined as a “Residential storm shelter.”
Residential storm shelter. A storm shelter serving occupants of dwelling units and having an occupant load not exceeding 16 persons.
Definitions
AREAS OF CONCENTRATED FURNISHINGS. 
•	Fixed furniture or partitions

AREAS OF UNCONCENTRATED FURNISHINGS. 
•	Moveable furniture

AREAS OF OPEN PLAN FURNISHINGS. 
•	Moveable furniture and no walls
Definitions
HAZARDS.
Collapse. Debris from wind damage to adjacent, taller structures that could fall onto the shelter.
Laydown. Nearby structures such as towers or large trees that could fall onto the shelter, if the shelter is within the laydown radius of the structure.
Rollover. Vehicles and small buildings, such as temporary classroom buildings, that could roll over due to extreme winds and impact the shelter.
Definitions
IMPACT-PROTECTIVE SYSTEM. A system or device such as a shutter, door or other device mounted on the inside or outside of the exterior wall of a shelter that has been demonstrated by testing to be capable of withstanding the impact of test missiles as detailed in this standard.

REBOUND IMPACT. The rebound impact by a test missile, or fragments thereof, on a portion of the shelter protective envelope after the test missile has impacted another surface of the shelter protective envelope.

Definitions
PROTECTED OCCUPANT AREA. 
SHELTER ENTRY SYSTEM, ALCOVE. 
SHELTER ENTRY SYSTEM, BAFFLED. 

Chapter 3 – 
Structural Design Criteria
Chapter 6 - Fire Safety
Application
•	Provides design requirements to resists high wind pressures and flying debris.  

Application
•	Provide construction requirements for:
•	The main wind resisting structural system
•	Components and cladding.  
•	Basic occupant life safety and health requirements
Structural Features
•	Water loads
•	Wind loads
•	Debris
•	Other concerns
Water loads 
•	Rain loads
•	6” per hour in addition to rate in maps
•	Hydrostatic loads
•	Flood loads
Wind loads
•	Wind load contour maps
•	Hurricanes
•	Atlantic coast and Gulf of Mexico
•	Hawaii, Puerto Rico, Guam and Virgin Islands
•	Tornado
•	Mid-west and eastern states
•	Alaska, American Samoa, Guam, Hawaii, Puerto Rice, Virgin Islands

Wind loads
•	Modifications to ASCE 7 Method 2
•	Wind directional factor, K_d
•	Importance factor, I
•	Exposure category
•	Topographic effects, K_zt
•	Enclosure classification
•	Atmospheric Pressure Change, APC 
Debris
•	Research based on compact, rod and plate type missiles.
•	Test methodology for testing walls, doors, shutters, and windows for impact from flying debris
•	The debris missiles expected for tornadoes is considerably higher than hurricanes

Other structural issues

•	Component design and testing;
•	Weather protection; 
•	Enclosure within a ‘host’ building; 
•	Connection of the shelter to foundations or slabs; 
•	Penetration of the shelter envelope by systems and utilities.

Other structural issues

•	Because fires often break out during or after a storm, where IBC requires fire barriers and horizontal assemblies with a fire-resistance-rating, where this is also a shelter wall or ceiling, it must be at least 2 hours.

Chapter 4
Siting
Travel distance
•	IBC says commercial tornado shelters at schools have to be within the building or less than 1000’ from an exterior door of the building to the door of the shelter (IBC Section 423.4.2)
•	ICC 500 says residential shelter have to be within the building or less than 150’ from an exterior door of the home to the door of the shelter (ICC 500 Section 403)
Flood provisions
•	Both commercial and residential shelters have to be elevated to limit the chance of flooding
•	Option differ based on if this is a tornado or hurricane, commercial or residential
•	Hurricane shelter will consider storm surge and costal wave effects
•	Considerations may include 
•	2’ above the 100 year flood elevation and 
•	Above the 500 year flood elevation
•	Above the highest recorded floor elevation
Safety provisions
•	Shelters must be protected from the possible release of any high hazard materials in the building
•	Shelters must not be located in Costal V zones on in the Floodway.
Chapter 5 - Occupancy, Means of Egress and Accessibility
Chapter 7 - Shelter essential features and accessories
Application
•	Basic occupant life safety and health requirements include:
•	Accessibility
•	Means of egress
•	Lighting
•	Sanitation
•	Ventilation
•	Fire Safety
•	Minimum required floor space per occupants

Essential Features

•	Occupant density
•	Number of doorways
•	Emergency escape
•	Ventilation
•	Potable water and sanitation
•	Emergency features
•	Location
•	Accessibility

Occupant Density
•	Community shelters
•	Hurricanes 
•	20 sq.ft. per person
•	Wheelchair – 20 sq.ft.
•	Bedridden – 40 sq.ft.
•	Tornadoes 
•	5 sq.ft. per person
•	Wheelchair – 10 sq.ft.
•	Bedridden – 30 sq.ft.

Occupant Density
•	Residential shelters
•	One- and two- family residential shelters
•	Hurricanes 7 sq.ft. per person
•	Tornadoes 3 sq.ft. per person
•	Larger residential shelters
•	Hurricanes 10 sq.ft. per person
•	Tornadoes 5 sq.ft. per person

Number of doorways & Emergency Escape
•	Number of exits for primary occupancy during normal use, not the occupant load of the shelter
•	When a community shelter has a single exit, a 2^nd emergency escape opening is required
Ventilation
•	Minimum ventilation openings required
•	Based on:
•	Tornado or hurricane shelter
•	Residential or community
•	Occupant load of community shelter  greater than 50
Potable water and sanitation facilities
•	Toilet facilities higher for hurricane shelters due to length of stay
•	Can use toilets within shelter if they can be converted for emergency mode
•	Toilets can be chemical toilets.
•	Hurricane shelters must have supply and storage for potable and waste water.
Emergency features
•	Tornado shelters
•	Fire extinguishers, first aid kits
•	Community shelter must have emergency lighting
•	Hurricane shelters
•	Fire extinguishers, first aid kits, emergency lighting
•	Community shelters with greater than 50 occupants must have standby power and lighting

Location & Accessibility
•	Community shelters must be on an accessible route
•	Residential shelters can be accessed by a stairway, ladder or alternating tread device

Chapter 8
Test methods for impact and pressure testing
Testing Protocol
•	Impact testing
•	Pressure testing
Chapter 9
Referenced standards
Referenced Standards
•	The full name of any standards referenced in the text, the edition and information on the promulgator are found in Chapter 6.
•	If you look up a standard, you will also see the section where that standard is referenced.
Summary
•	Building codes require that buildings be able to withstand a “design” wind event. 
•	Most tornado-prone regions, the building code design wind event is a wind event with 90 mph winds. 
•	Hurricane-prone areas, design wind events in the code range from 90 to 150 mph. 
•	A tornado or extreme hurricane can cause winds much greater than those on which local code requirements are based. 
•	Having a home built to “code” does not mean that your home can withstand wind from an extreme weather event.
Summary
•	Home or small business owners should assess their risk and determine the best type of safe room for their needs.
•	A safe room is the preferred method of wind protection in high-risk areas.  
•	IBC Section 423 does not require storm shelters in most occupancies, but does require compliance with ICC 500 if someone wants to build a shelter. 
•	Storm shelters are required in schools and buildings housing people we need for emergency response after the storm

Summary
•	Having a shelter can reduce injury and death.
•	Evacuation plans must be made known and practiced. 

Is your area in tornado alley?
Would a tornado shelter be required?
Would a hurricane shelter be required?
Your comments?
•	What in this section might you be able to use in your own work?
•	What could you best share with others in as part of a collaborative effort?

Thank you for participating

To schedule a seminar, contact:

The ICC Training & Education Department
1-888-ICC-SAFE (422-7233) Ext. 33818
or
E-mail:   icctraining@iccsafe.org