Reinforcing or “beefing up” a building might be referred to as the “fortress solution.” A collateral approach might be to protect a building’s structural system as well as its vital vertical systems for fatal damage, while at the same time permitting violent impacts or explosions to expend themselves on more absorbent flexible materials.

A building that has a considerable amount of glazing at the sidewalk level might (depending on the security goals) be a candidate for replacement of the existing glazing (probably a heavyweight, tempered plate glass) with laminated safety glass. This type of glass is being specified in some building codes in areas where hurricanes are prevalent. (Laminated safety glass is similar to the glass in windshields of automobiles, while tempered glass is the same sort as in storm doors or shower doors.)

Laminated safety glass is constructed of two layers of glass with a layer of plastic sandwiched in between. It is much stronger than tempered glass due to the behavior of the plastic (polycarbonate or polyvinylbutryl) internal layer, depending on its particular specification. It will withstand a substantial impact, as might be delivered by a sharp blow, and, if thick enough, a bullet. The sheet of glass receiving the impact begins to shatter, absorbing a portion of the projectile’s energy. The inner plastic sheet flexes, while at the same time gripping the glass shards. The glass system bends without shattering and collapsing, thus preventing potentially lethal flying glass shards. Because safety plate glass has increased rigidity, it is less likely to pop out of its frame during a high wind, such as might be experiences in a tornado or hurricane, and can be an effective deterrent against flying debris.

Window Coverings
A somewhat recent and effective solution to explosive blasts is the use of specially manufactured and fabricated window covering curtains or drapes. These drapes are effective in stopping ballistic glass shards that result from an explosive force or wind-borne objects, such as tree limbs or other debris. They function by yielding inward with the thrust of the explosion and catching the glass pieces in the web of the fabric.

Excerpted with permission from Building Security: Strategies & Costs by David Owen, published by RSMeans.