FEMA 453 Design Guidance for Shelters and Safe Rooms

façade materials intact and attached to the building. Brittle modes
of failure must be avoided to allow ductile deformations to occur.
2.3.4 Forced entry and Ballistic resistance
Ballistic-resistant design involves both the blocking of sightlines to
conceal the occupants and the use of ballistic-resistant materials
to minimize the effectiveness of the weapon. To reduce exposure,
the safe room should be located as far as possible into the
interior of the facility and walls should be arranged to eliminate
sightlines through doorways. In order to provide the required
level of resistance, the walls must be constructed using the appropriate
thickness of ballistic-resistant materials, such as reinforced
concrete, masonry, mild steel plate, or composite materials. The
required thickness of these materials depends on the level of
ballistic resistance; however, resistance to a high level of ballistic
threat may be achieved using 6.5 inches of reinforced concrete,
8 inches of grouted concrete masonry unit (CMU) or brick, 1
inch mild steel plate, or ¾ inch armor steel plate. A ½-inch thick
layer of bullet-resistant fiberglass may provide resistance up to a
medium level of ballistic threat. Bullet-resistant doors are required
for a high level of protection; however, hollow steel or steel clad
doors with pressed steel frames may be used with an appropriate
concealed entryway. Ballistic-resistant window assemblies contain
multiple layers of laminated glass or polycarbonate materials and
steel frames. Because these assemblies tend to be both heavy and
expensive, their number and size should be minimized. Roof
structures should contain materials similar to the ballistic-resistant
wall assemblies. Ratings of bullet-resisting materials are presented
in Table 2-1.
Structural deSign criteria
2-