The deaths of eight students at a school struck by a tornado in Enterprise, Alabama in 2007 and the deaths of seven others when a tornado struck a school in Moore, Oklahoma in 2013 have spurred building code writers to make the protection of students from tornadoes a priority in the 17 U.S. states commonly referred to as “tornado alley.”
The International Building Code 2015 requires new schools in those states to be built with tornado shelters—which is a step in the right direction.
But for the approximately 40,000 existing school buildings, averaging 40 years in age, it’s no step at all. School administrators in those facilities have limited options for providing tornado protection. They can:
- build new additions to serve as tornado safe rooms,
- find places of refuge in existing school buildings,
- or retrofit portions of existing school buildings to become tornado safe rooms.
Each of these options presents restrictive challenges for architects and engineers; however, through designing tornado shelters I have become convinced that if we in the design and construction community focus on the issues we can find creative and cost effective solutions that apply the best-in-class construction materials and technologies to save lives.
New additions can be problematic. If the space is dedicated to serve only as a shelter, or even if it is dedicated to serve as a shelter plus new space for school functions, there can be drawbacks. Administrators must factor in the travel time associated with moving an entire school population from various parts of a campus into the shelter during a tornadic event, which could require students to travel outside during hazardous weather. Moreover, if the addition is also to serve as a classroom or gymnasium, the area usable as a shelter will be reduced by the furnishings, meaning the addition may need to be larger and more costly than what is required for a shelter alone. The logistical difficulties and reduced economic efficiencies can make this option less attractive.
As far as finding places of refuge in existing buildings, for a long time we have been fooling ourselves. Historically, interior corridors have been determined to be the safest location for students to take shelter during a tornado. Short roof spans and concrete masonry corridor walls, and their close proximity to classrooms has often led to the selection of corridors as the safest place for students during storms.
However, typical school corridors do not qualify in any way as tornado shelters. Considering that the wind pressures associated with a design level, or 250-mph, tornado are more than seven times higher than the pressures used to design buildings in non-coastal areas and that shelters are subject to wind-borne debris impacting surfaces at speeds of up to 100 mph, it becomes obvious that corridors built to standards less than ICC 500 ICC/NSSA Standard for the Design and Construction of Storm Shelters will not provide real tornado safety.
That leaves us with the third option of retrofitting existing areas to create true storm shelters in many of those 40,000 schools.
Jim Waller, PE, of Remagen SafeRooms and I have been collaborating to design a system for retrofitting classroom corridors with ICC 500 and FEMA 361-compliant tornado shelters. We have developed these tornado shelter designs for three elementary schools in Henry County, Tennessee, which we believe offer a new solution for retrofitting tornado safe rooms within existing schools.
The systems use rigid steel frames and patented, prefabricated light gauge steel enclosure components to sleeve the existing schools’ corridors with a structure designed to resist the wind pressures and debris impacts of an EF-5 tornado.