3 things to consider when designing a storm shelter for your school

It’s officially storm season in tornado alley, and as an architect for education projects, keeping students safe is top of mind. I’m a member of the National Storm Shelter Association’s (NSSA) Design Practices Committee, and the association’s purpose is to ensure its members produce the highest quality residential and community storm shelters for protecting people from injury or loss of life from the effects of tornadoes and other wind-related events.

The 2018 International Building Code (IBC) requires that all Group E occupancies that fall within FEMA’s 250 mph wind speed map with an occupant load of 50 or more have a storm shelter constructed in accordance with ICC 500, the ICC/NSSA standard for the design and construction of storm shelters. The required capacity of the storm shelter is intended to be the expected number of students and staff on any given day or the capacity of the largest indoor assembly space, whichever is greater. The 2018 International Existing Building Code (IEBC) clarifies that an addition requires a storm shelter but is only required to house the occupant load of the addition, not the entire existing building or campus, if the addition is not otherwise planned to be large enough.

The ICC 500 provides minimum design and construction requirements from structural design criteria, occupant density, critical support systems, and impact and pressure testing to name a few.

From my team’s standpoint, our goal is to provide a shelter that protects its occupants and to ensure we’ve designed everything you might need to maintain safety, communications, and comfort.  When designing storm shelters for K12 schools, there are three things to consider. 

1. Location 

A storm shelter may be free standing, attached to, or within a building. Chapter 4 Siting of the ICC 500 focuses on flood elevation, but the location also needs to be carefully analyzed for adjacent building collapse, debris, and proximity. Both the 2018 IBC and IEBC limit the travel distance from any building served by the shelter to 1,000 feet.

We’ve designed several basement level or subgrade parking structure shelters when those spaces were already part of the programmed design. A shelter covered by more than 12 inches of soil does not need to be impact tested. However, a basement level shelter with occupied floors above needs to be designed to withstand the collapse (impact) of the structure above, although any shelter that’s within a building’s fall zone would also need to resist the same.

In most schools, we are designing either a portion of a classroom wing or the gymnasium as the storm shelter. There are many things to consider, including occupant density, access, sanitation facilities, and impact protective systems (doors, window shutters.) Determining the right location for each project is not a one-size or location-fits-all scenario.

2. Critical support systems

ICC 500 defines critical support systems as structures, equipment, and components required to ensure the health, safety, and well-being of occupants. The standard requires we provide critical support systems for two hours for a tornado shelter and 24 hours for a hurricane shelter, including functioning toilets, hand-washing stations (in some cases, portable units), a fire extinguisher, a place for a first aid kit, lights on back-up or battery power, and ventilation (mechanical or natural). 

Should there be a loss of power, Uninterruptible Power Supplies (UPS) or a generator will be required to maintain emergency lighting, any plumbing supply/waste systems or sump pumps, and mechanical ventilation. Natural ventilation is preferred since most mechanical equipment is typically on the exterior and difficult to integrate within or protect against 250 mph winds. Comfort of occupants and certainly cost are considerations.

The most efficient shelters are those that function as classrooms or gymnasiums when not in use as a shelter and, therefore, have the least amount of additional storm shelter only spaces or features. Integrating the required sanitation facilities is often challenging, but the required number of fixtures is a fraction of what is required under the normal use of the space, whether a classroom or gym. We’ve found creative solutions will limit cost impacts.

3. Operations and maintenance (O&M)

Anything not considered life safety is user-defined, which may include communication systems such as a dedicated land line, wireless access point, TV with cable connection for weather and news, or power for charging two-way radios and cell phones.  Convenience outlets on back-up power will serve these items, and refrigeration for medicine is also a consideration. We often provide a control room where shelter equipment is located and for emergency supplies such as food and bottled water.

The ICC 500 requires that a Local Emergency Planning Committee (LEPC) be in place and responsible for local emergency planning. In the case of a school, this would typically be a committee appointed by the school board. FEMA outlines several operations and maintenance considerations for shelters including staffing, roles and responsibilities, access and entry, lockdown, and several maintenance concerns.

It is important to note that O&M drives the design, and we recommend our clients form a collaborative planning team, whether it be the LEPC or a subcommittee to help steer this process.We work with our clients to understand how they intend to operate the shelter, so we can design features that meet their particular needs. For instance, given the age of elementary students, their needs will vary from a shelter we design for a high school. Younger students may require a higher level of comfort and more distractions for longer periods.

Whether designing for 200 or 2,000 occupants, from elementary to high school ages, there is a lot to consider in addition to location, critical support systems, and operations and maintenance. We want to offer our clients expertise and design options that meet their needs while integrating all necessary components for a shelter to protect their occupants.