Designing and constructing to these higher standards and beyond building codes does come with increased financial investment.
Storm shelters and safe rooms to protect residents
A storm shelter or safe room is a hardened structure designed to provide near-absolute protection during extreme weather events. ICFs are not impacted by drought or extreme heat or cold. The ICF structure in flooded buildings can often be dried out and restored because they do not contain biodegradable materials subject to mould. This is not the case for wood structures, some may need rebuilding from the ground up to reach areas of the structure which are not underwater.
In areas prone to hurricanes and tornadoes, storm shelters can be a fast, effective way to shield vulnerable communities until larger infrastructure can be retrofitted or replaced with more resilient features.
In 2008, the U.S., via the International Code Council (ICC) and National Storm Shelter Association (NSSA) first developed the ICC/NSSA Standard for the Design and Construction of Storm Shelters, also known as ICC 500. This outlines proper design, construction, and inspection of residential and community storm shelters, including considerations such as building materials, structural testing, occupant density, ventilation, and signage.
A residential safe room can be built within a home or as a stand-alone structure adjacent to a residence to accommodate no more than 16 individuals. A community storm shelter, on the other hand, is intended to hold anywhere from 16 to several hundred people.
The Federal Emergency Management Agency (FEMA) has its own guidelines for residential and community storm shelters, which they refer to as “safe rooms” in FEMA 320 and FEMA 361.4
Both ICC 500 and FEMA offer criteria for a structure’s ability to withstand wind loads, rain loads, hydrostatic loads, pressure differentials, and wind-borne debris loads.
Regions of the U.S. that fall within the 402 km/h (250 mph) wind-speed zone for tornadoes are required to have ICC 500-compliant storm shelters with the following building types:5
- K-12 schools
- Daycare facilities
- Emergency operation centres
- Fire, rescue, and ambulance stations
- Police stations
- 911 call centres
- Military installations
It is important to note how the design criteria for tornado and hurricane shelters differs due to the varying wind pressure, speed, and duration of the storms. Other factors impact the execution of these codes based on a structure’s occupant density, water supply, ventilation, and access to emergency power.
The National Building Code of Canada (NBC 2020) offers similar design criteria through importance categories, which can be determined by the NBC forming Part of Sentence 4.1.2.1.(3) Table 4.1.2.1.B.:
- Low Importance—low direct or indirect hazard to human life
- Normal Importance—all buildings not otherwise defined
- High Importance—buildings likely to be used as post-disaster shelters with a primary use as a school or community centre
- Post-disaster buildings
The post-disaster building category best reflects the ICC500 and FEMA guidelines for storm shelters in the U.S. For the definition of a post-disaster building category, the NBC Part 1 A-1.4.1.2 identifies essential structures and their services (Figure 1). All buildings under the definition of a post-disaster building must retain a professional engineer to undertake responsibility of the design to Part 4 of the NBC.
