Life Safety

Best Practices in Tornado Resistant Construction - Utilize ICB in a Continuous Load Path

Tor­na­do-resis­tant con­struc­tion is essen­tial in the Unit­ed States where an aver­age of 1253 tor­na­does occur annu­al­ly and can pro­duce wind speeds of more than 200 mph. Because tor­na­does are unpre­dictable and vio­lent, their destruc­tion is often wide­spread. Accord­ing to the Nation­al Ocean­ic and Atmos­pher­ic Admin­is­tra­tion (NOAA) tor­na­does cause an aver­age of 60 – 65 fatal­i­ties and 1,500 injuries each year. Tor­na­do Alley is hit par­tic­u­lar­ly hard by the occur­rence of tor­na­does. Tor­na­do Alley is unof­fi­cial­ly a region from cen­tral Texas, north­ward to north­ern Iowa, and from cen­tral Kansas and Nebras­ka east to west­ern Ohio. It is a region where cold, dry air from the north­west, warm dry air from the south­west, and warm, wet air from the south­east clash. The col­li­sion of these three weath­er sys­tems fre­quent­ly results in intense thun­der­storms and vio­lent tor­na­does. In Texas alone, between the years of 1991 and 2010, there was an annu­al aver­age of 155 tor­na­does, more than any oth­er State. In addi­tion, Texas aver­ages annu­al­ly 2.8, EF-31 to EF‑5 tor­na­does. Tor­na­do resis­tant con­struc­tion is essen­tial for the pro­tec­tion of a build­ing and its occu­pants from dis­as­trous out­comes dur­ing a tor­na­do emer­gency.

A Continuous Load Path Protects a Building's Integrity When Under Attack from a Tornado

FEMA high­ly rec­om­mends a safe room for max­i­mum safe­ty to a build­ing’s occu­pants dur­ing a tor­na­do emer­gency. How­ev­er, a tor­na­do-resilient design of the entire build­ing is ulti­mate­ly the best pro­tec­tion of lives and the struc­ture. A con­tin­u­ous load path is the best defense towards hold­ing a build­ing togeth­er when the high winds of a tor­na­do try to pull it apart. The con­tin­u­ous load path ensures that when a load, includ­ing lat­er­al (hor­i­zon­tal) and uplift loads, attacks a build­ing, the load will move from the roof, wall and oth­er com­po­nents toward the foun­da­tion and into the ground. A strong con­tin­u­ous load path is essen­tial to hold­ing the roof, walls, floors and foun­da­tion togeth­er dur­ing a tor­na­do or oth­er extreme wind event.

Insulated Concrete Blocks Build Tornado Resistant Buildings

Build­ings con­struct­ed with insu­lat­ed con­crete blocks (ICB) main­tain their integri­ty dur­ing the intense winds of a tor­na­do. Insu­lat­ing con­crete blocks can with­stand winds of over 200 mph. Build­ings con­struct­ed of con­crete blocks are much stronger than wood and steel-framed build­ings under severe wind events. In fact, a study pub­lished by the Port­land Cement Asso­ci­a­tion (PCA), com­pared the struc­tur­al load resis­tance of insu­lat­ing con­crete form (ICF) walls to con­ven­tion­al­ly framed walls. The study con­clud­ed that con­crete walls have a much high­er struc­tur­al capac­i­ty and stiff­ness to resist the in-plane shear forces of high wind than wood or steel framed walls. The strength of con­crete walls results in less lat­er­al twists and dam­age to non-struc­tur­al ele­ments of a build­ing such as the plumb­ing and elec­tri­cal. Uti­liz­ing insu­lat­ed con­crete blocks for tor­na­do-resis­tant con­struc­tion can main­tain a build­ing’s integri­ty dur­ing a strong tor­na­do event.

Insu­lat­ed con­crete blocks (ICB) can also resist dam­age from fly­ing debris trav­el­ing over 100 mph. A study by Texas Tech Uni­ver­si­ty com­pared the impact resis­tance of wind dri­ven debris between ICF walls and con­ven­tion­al­ly framed walls. The study found that ICF walls resist the impact of wind dri­ven debris. Con­ven­tion­al framed walls, how­ev­er, failed to stop the pen­e­tra­tion of air­borne haz­ards. Insu­lat­ed con­crete walls are the best pro­tec­tion from wind­blown debris to a build­ing and its occu­pants.

The Bautex Wall System Stands up to a Tornado’s Strength

The Bau­tex Wall Sys­tem has the strength to resist the heavy winds and fly­ing debris of the strongest tor­na­do. The Blocks meet the Fed­er­al Emer­gency Man­age­ment Agency FEMA 320 and FEMA 361 guide­lines in storm zones with wind speeds up to 250 miles per hour. The Bau­tex Block also has the strength and mass to resist the impact to wind dri­ven debris at speeds greater than 100 mph. In addi­tion to severe weath­er resis­tance, Bau­tex Blocks have the ther­mal per­for­mance required by the IRC and IBC and are fire-rat­ed, noise-reduc­ing, and easy to install. Bau­tex Walls are a good choice when design­ing for tor­na­do-resis­tant con­struc­tion.

The National Weather Service Ratings of Tornadoes - EF-Scale

In 2007, the Nation­al Weath­er Ser­vice imple­ment­ed the Enhanced Fuji­ta Scale (EF-Scale). The scale deter­mines a tor­nado’s strength based on the destruc­tion it caused. The scale ranges from one to five, with five being the most intense. The EF-Scale con­sid­ers 28 dam­age indi­ca­tors such as build­ing type, struc­tures, and trees. Each dam­age indi­ca­tor has eight degrees of dam­age rang­ing from the begin­ning of vis­i­ble dam­age to com­plete destruc­tion of the dam­age indi­ca­tor.

A safe room is a space with­in or near­by a build­ing, that pro­vides near per­fect pro­tec­tion dur­ing tor­na­does and hur­ri­canes, accord­ing to FEMA guide­lines. A FEMA safe room is designed and con­struct­ed as spec­i­fied in FEMA P‑361, and FEMA P‑320.