Bullet proof glass gets the most attention, but it’s obviously pretty useless to have a bullet-stopping window set in a very bullet-permeable wall. Bullet proof walls may also be required.
Interior Bullet Proof Walls
There are essentially two options when building a new bullet proof interior wall: “metal-stud” construction or “panel construction.” The difference is largely aesthetic, rather than in performance.
“Metal-Stud” Style Bullet Proof Walls
Most normal walls are “stud walls.” In home construction, this means the wall is framed out with two-by-four studs, and drywall is hung on this frame. The drywall is then “taped and mudded” (i.e., the seams and nail-pops are covered with a plaster-like finish), sanded (to make the surface smooth), and painted. Commercial construction isn’t that different, but for fire-safety and energy efficiency the wood studs are replaced by metal studs made from thin-gauge steel with a “C”-shaped cross section. Apart from that, the construction is identical: Frame the wall, hang the drywall, tape the seams, mud the surface, sand it down, and paint it up.
A “metal stud” bullet proof wall starts with this same frame, but instead of attaching the drywall directly to that frame, an intervening layer of bullet resistant fiberglass is screwed and glued to the studs (with four-inch wide interior bullet proof “batten strips” backing the seams in the bullet proof panels). Drywall is then attached to the fiberglass and finished as usual. The resulting wall is entirely indistinguishable from any “normal” wall. Total stealth security.
“Panel” Style Bullet Proof Walls
Inconspicuous white walls aren’t a good fit for every company’s aesthetic. In these cases, bulletproof companies like Total Security Solutions frame the wall in sections using ballistically rated square-profile aluminum tubes–similar to the thick mullions on a window-wall. Each framed section then holds a panel made from a sheet of three-quarter-inch plywood epoxied to a sheet of bullet resistant fiberglass that is, in turn, covered by a thin finishing veneer. These veneers can be any type of wood, plastic, or an aluminum skin, giving enormous flexibility for the final look and feel of the bullet proof wall. Panel walls make a subtle–but persuasive–argument for the stability, permanence, and security a business values.
Exterior Bullet Proof Walls
Fortunately, most commercial building materials used in exterior walls inherently offer decent bullet resistance. Poured concrete, cinderblock, and even lowly red-brick veneer will, for all practical purposes, stop any common domestic bullet. “These aren’t bullet proof walls,” Total Security Solutions vice president Jim Richards warns, “but there’s enough material there to slow down bullets and keep them from popping through.”
Unfortunately, commercial builders are increasingly turning to exterior insulation finishing system (or EIFS) for their exteriors. While these finishes often look like concrete–or even granite–they are actually made of a layer of thick polystyrene foam (akin to the styrofoam used for take-away coffee cups and carry-out boxes) covered in nylon mesh coated in a thin layer of concrete-like finish. While EIFS offers excellent energy efficiency and ease of installation, it’s not going to do much to slow even a low-caliber bullet.
In buildings with EIFS exteriors–including most newer government buildings–Jim has advised clients that it’s best to treat these exterior walls as susceptible to the same threats as the interior walls, and harden them with sheets of bullet resistant fiberglass.
Steel vs. Dupont™ Kevlar® Fiber in Bullet Proof Walls
Bullet proof fiberglass isn’t your only option if you need a bullet proof wall. In many situations good ole stainless steel continues to perform well–and is significantly less expensive (in terms of raw materials). Nonetheless, Jim finds that fiberglass is almost five times more popular than steel among his customers. He attributes this to fiberglass’s lower total cost and higher reliability.
Steel may cost less per square foot, but its added weight (twice that of bullet resistant fiberglass) means that walls almost invariably need to be reinforced to accommodate the weight of the steel panels. On top of that, steel cannot be trimmed or drilled on site. If an initial measurement turns out to be off, or the client wants a last minute change, those heavy sheets of steel have to be hauled back to the shop for trimming. Added expense in steel fabrication and installation absorbs much of the initial cost savings in materials.
But cost isn’t the key issue. “It’s tough to get an overall ballistic rating on steel-backed bullet proof walls,” Jim explains, ”because the trueness of the material is always in question.” Unlike modern pultruded ballistic fiberglass, steel is still not a consistent product. A visual inspection of a sheet of steel will never uncover a void within the metal, fundamental structural imperfections, or microscopic fractures that could collapse under the pressure of a bullet. No one wants to invest in a suspect bullet proof wall.