News Article

Residential Safe Room Design

A res­i­den­tial safe room protects the occupants of a home or small business from the high wind forces of a tornado or hurricane. Safe rooms are essential in the United States where an average of 1,253 tornadoes occur yearly, creating wind speeds of 200 mph or more. Between the years of 1991 and 2010, Texas alone expe­ri­enced an annual average of 155 tornadoes, more than any other state. The impact of tornadoes and hur­ri­canes is dev­as­tat­ing. The National Oceanic and Atmos­pher­ic Admin­is­tra­tion (NOAA) reports that tornadoes cause an average of 60 – 65 fatal­i­ties and 1,500 injuries each year. In 2017, Hur­ri­canes Harvey and Irma took 143 lives. CNN reports that 500 people have died as a result of Hurricane Maria, with 113 people still missing. An added benefit of a safe room is it increases a home’s value. In fact, a study by Professor Kevin Simmons, an economist with Austin College and the Federal Alliance for Safe Homes concluded safe rooms increase a home’s value by approx­i­mate­ly $4,200, or on average 3.5 percent. Res­i­den­tial safe rooms are a good invest­ment and essential for pro­tect­ing the occupants of a home or small business from disaster during high wind events, like tornados and hurricanes.

Design Standards and Guidelines for Residential Safe Room Design

The ICC-500 is the Inter­na­tion­al Code Council’s and the National Storm Shelter Asso­ci­a­tion (NSSA) standard (ICC/​NSSA) for the Design and Con­struc­tion of Storm Shelters (safe rooms). The 2014 ICC-500 is the most current ICC/​NSSA standards for con­struc­tion and design and con­struc­tion of res­i­den­tial and community storm shelters. Since 2009, the Inter­na­tion­al Building Code (IBC, Section 423) and the Inter­na­tion­al Res­i­den­tial Code (IRC, Section R323) have utilized ICC-500 as their reference standard for building storm shelters.

The Federal Emergency Man­age­ment Asso­ci­a­tion guide­lines are found in FEMA P‑320,Taking Shelter from the Storm: Building a Safe Room for Your Home or Small Business and FEMA P‑361, Safe Rooms for Tornadoes and Hur­ri­canes: Guidance for Community and Res­i­den­tial Safe Rooms. Both FEMA documents use ICC-500 as a ref­er­enced standard, however, the FEMA standards for safe rooms are con­sid­ered slightly more con­ser­v­a­tive than the standard for ICC-500 storm shelters. The ICC-500 is the reference standard for the design and con­struc­tion of storm shelters that will protect the occupants of a business or home during wind storm events. Res­i­den­tial safe rooms designed to FEMA guide­lines offer occupants of homes and small busi­ness­es near-absolute pro­tec­tion” against severe wind events.

Designing an ICC-500 Residential Storm Shelter

An ICC-500 res­i­den­tial storm shelter is a solid structure designed to meet IRC/​ICC spec­i­fi­ca­tions and provide the occupants of a home a degree of life safety in extreme weather events, including tornadoes and hurricanes.The design and con­struc­tion of an ICC-500 res­i­den­tial storm shelter must follow the guide­lines specified in the ICC-500 standard (here is a free summary provided by FEMA). Key elements of an ICC-500 res­i­den­tial storm shelter are a strong con­tin­u­ous load path, and resis­tance to over­turn­ing, uplift, and windborne debris.

Residential Storm Shelter Design must have a Continuous Load Path

A strong con­tin­u­ous load path is critical to holding the roof, walls, and foun­da­tion of a res­i­den­tial storm shelter together during an extreme wind event. The shear walls1 of the storm shelter is the primary component of the con­tin­u­ous load path that combats the lateral-loads (hor­i­zon­tal wind forces). High winds trav­el­ling over the roof of the storm shelter creates uplift forces that pull on the walls. Winds hitting the windward side of the safe room impart lateral pushing forces on the wall and the movement of air around the leeward side of the structure causes suction pulling on the walls in the direction of wind travel. The walls of the storm shelter must maintain their integrity and transfer all of these loads to the foun­da­tion. The foun­da­tion must also be designed to resist any over­turn­ing of the structure due to the combined forces of the wind.

The Bautex™ Block Wall System is an excellent product for a res­i­den­tial storm shelter. The steel rein­forced concrete poured inside the Bautex Blocks have the con­tin­u­ous load path required to resist extreme wind events during tornadoes and hur­ri­canes. Bautex Blocks meet the ICC-500 guide­lines in areas with maximum wind speeds up to 225 mph. Essential to the design of a res­i­den­tial storm shelter is a con­tin­u­ous load path. Crucial to the con­tin­u­ous load path of a res­i­den­tial storm shelter is a strong wall system that can also support the roof, like the Bautex™ Block Wall System.

Residential Storm Shelter Design Resists Overturning and Uplift

The foun­da­tion of a res­i­den­tial storm shelter must be anchored so to resist over­turn­ing and uplift as it receives the wind loads from of the walls. The design and anchoring of the foun­da­tion must follow the guide­lines in the ICC-500 standard (Section 308.1.1.2) which mandates that the design of slab-on-grade foun­da­tions be designed for the applic­a­ble loads and must at a minimum be 3.5 inches thick, contain steel rein­force­ment, and take into account the presence of slab joints” . During severe wind events, the foun­da­tion of a res­i­den­tial safe room must resist over­turn­ing, uplift, and sliding forces.

Residential Storm Shelters Must Protect Against Flying Debris

The roofs, walls, and doors of a res­i­den­tial storm shelter must resist the impact and pen­e­tra­tion of flying debris during a severe wind event. The roofs of a safe room must be built to resist the impact of a 15-pound wood 2×4 shot at 67 mph. The doors of a safe room should have doc­u­ment­ed proof that they are compliant with the most current version of FEMA P‑361 and FEMA P‑320 or the ICC 500 for tornado wind speed of 250 mph. Walls of an ICC-500 storm shelter must be built to resist the impact of a 15-pound wood 2×4 shot at 100 mph. The entire envelope of a res­i­den­tial safe room must protect the room’s occupants from flying debris during hur­ri­canes and tornadoes.

The Bautex Block Wall Assembly resists the impact and pen­e­tra­tion of flying debris during a severe wind event, which makes the Bautex Block an ideal material choice for a res­i­den­tial safe room. Specif­i­cal­ly, Bautex insulated concrete block has the mass and strength to resist the impact to wind-driven debris at speeds more than 100 mph. Also, The Bautex Blocks meets or exceeds the following ICC-500 FEMA standards for debris impact.

  • Series 1 FEMA 320361 Bautex Block Panel with Brick Veneer.
  • Series 2 FEMA 320361 Bautex Block Panel with CMU Block Veneer.
  • Test pro­jec­tile 15 lb. wooden 2‑inch X 4‑inch propelled at 100 mph.

A res­i­den­tial safe room protects the occupants of a home or small business during severe wind events. A res­i­den­tial safe room con­struct­ed with Bautex Blocks meets and exceeds the criteria for a FEMA res­i­den­tial safe room design for con­tin­u­ous load path and impact resis­tance. Visit Bautex Block Wall Systems for more infor­ma­tion on res­i­den­tial safe room design.

1Shear walls are a struc­tur­al system that provides lateral resis­tance to a building home, safe room, etc.