(a) Structural integrity criteria.
(1) The safe room shall be built with a complete structural system and a complete load path for vertical and lateral loads caused by gravity and wind.
(2) The building that the safe room is built within shall be assumed to be destroyed by the storm and shall not be taken as offering any protective shielding to the safe room enclosure.
(3) The ceiling structure and wall shall be capable of supporting a superimposed debris load of the full weight of any building floors and roof above, but not less than 125 psf.
(4) The safe room enclosure shall be capable of simultaneously resisting lateral and uplift wind pressures corresponding to a 160 mph 3-second peak gust, determined in accordance with ASCE Standard 7, Minimum Design Loads for Buildings and Other Structures, calculated using load and importance factors of 1.0. The site exposure factor shall be based on exposure C. The gust factor and the directionality factor shall be taken as 0.85. Topographic wind amplification caused by mountainous terrain shall be considered in accordance with the building code. Internal pressure shall be determined in accordance with ASCE-7.
(5) The safe room shall be anchored to a foundation system capable of resisting the above loading conditions.
(b) Windborne debris impact protection of building enclosure elements.
The entire enclosure of the safe room, including all walls, ceilings, and openings, fixed or operable windows, and all entry doors into the safe room, shall meet or exceed Level D requirements of ASTM E 1996 (Table 16.5-1). Any wall or ceiling penetration greater than 4 square inches shall be considered an opening.
Exception: Electrical outlet boxes and interior lighting switches not penetrating more than 2.5 inches into the interior wall surface and a plumbing piping or conduit not greater than 1.5 inches in diameter shall be exempted from this requirement.
Approved debris impact resistant wall assemblies. Wall assemblies constructed in accordance with Table 16-13.7(b) comply with the Level D windborne debris impact protection of building-enclosure elements.
Wall Assemblage |
3/4-inch plywood on wood studs at 16-inches on-center with #8 x 3-inch wood screws at 6-inches o.c. |
3/4-inch plywood attached to double studs at 16-inches o.c. with #8 x 3-inch wood screws at 6-inches o.c. |
8-1/4-inch cementitious lap siding over 22 ga sheet metal attached to 350S162-33 studs at 24 inch or 16 inch o.c. |
8-1/4 inch cementitious lap siding attached to 350S162-33 studs at 24 inch o.c. studs with interior 3/4 inch ply interior sheathing |
8-1/4-inch cementitious lap siding attached to 35US1b2-33 studs at 24 inch o.c. with 1/2 inch interior 22-gage sheet metal composite gypsum wallboard |
8-1/4-inch cementitious lap siding attached to 2 x 4 wood studs at 16 inch o.c. with 1/2 inch interior 22-gage sheet metal composite gypsum wallboard |
8-1/4-inch cementitious lap siding attached to 2 x 4 wood studs at 16 inch o.c. with 22-gage sheet metal and ½ inch interior gypsum wallboard |
Cementitious lap siding attached to 5/8 inch structural plywood on 2 x 4 wood studs @16 inches a/c. |
Cementitious-panel siding attached to 5/8 inch structural plywood on 2 x 4 or 362S-137-43 steel studs @ 16 inches o.c. |
EFS with 1/2-inch dens-glass gold exterior sheathing on 362S-137-43 steel studs @ 16 inches and 1/2-inch interior gypboard |
Interior or Exterior wall with laterally braced (sheathed) 2 x 4 wood studs at 16 inch o.c. with 22-gage sheet metal on either side attached directly to the studs |
Interior or Exterior wall with laterally braced (sheathed) 2 x 4 wood studs at 16 inch o.c. with 1/2 inch interior 22-gage sheet metal composite gypsum wallboard on either side attached directly to the studs |
24 gage steel sheet (50 ksi) on girts |
4-inch-thick concrete with reinforcing |
6-inch CMU with partial grouting at reinforcing spaced at 24 inches o.c. |
8-inch CMU with partial grouting at reinforcing spaced at 24 inches o.c. |
Notes: Sheathing shall be attached to studs at 6-inches on center edge and field fastening. 22 gage sheet metal shall be galvanized and attached to studs with screws |
(c) Cyclic pressure loading of glazing and protective systems.
Impact protective systems shall meet the ASTM E 1996 cyclic pressure requirement for the loading given in Table 16.13-1.
Residential Safe Rooms | |||
ASTM E 1996 Missile Level Rating | Debris Missile Size | Debris Impact Speed | Enclosure Wall Ceiling, and Floor Cyclic Air Pressure Testing— maximum inward and maximum outward pressures |
D | 2 x 4 weighing 9.0 lb. +/- 0.25 lb., and with min. length 8 ft. +/- 4-inch | 50 ft./sec. or at least 34 mph | 35 psf inward 45 psf outward |
(1990 Code, Ch. 16, Art. 13, § 16-13.7) (Added by Ord. 12-34)