Building a safe room that can handle wind, rain, and flying debris

(a) Structural integrity criteria. (1) The residential safe room must be built with a complete structural system and a complete load path for vertical and lateral loads caused by gravity and wind. (2) The ceiling structure and wall must be capable of supporting a superimposed debris dead load of the full weight of any building floors and roof above, but not less than 60 psf. (3) The residential safe room enclosure must be capable of simultaneously resisting lateral and uplift with pressures corresponding to a 145 mph 3-second peak gust ultimate design wind speed, determined in accordance with ASCE-7, Minimum Design Loads for Buildings and Other Structures. The site exposure factor must be based on exposure C or the exposure zone shown in State Building Code Appendix W Figure 1609.4, whichever is greater. The values for the gust factor and the directionality factor must be taken as 0.85. Topographic wind amplification caused by mountainous terrain must be considered in accordance with the building code. Internal pressure must be determined in accordance with ASCE-7. (b) Windborne debris impact protection of building enclosure elements. The exterior walls, vents, openings, fixed or operable windows, and entry doors into the safe room, must meet or exceed Level D requirements of ASTM E 1996 (Table 422.5-1), or be an approved assembly listed in this article. The interior walls, doors, openings, and ceilings into the safe room must meet or exceed Level C requirements of ASTM E 1996 (Table 422.5-1), or be an approved assembly listed in State Building Code Appendix U Section 429.5.2. Any exterior wall penetrations greater than 36 square inches must be considered an opening. (c) Debris impact and cyclic pressure loading of glazing and protective systems. Impact protective systems must meet the ASTM E 1996 cyclic pressure requirement for the loading given in Table 16.13.1 . Table 16.13-1: Windborne Debris Protection and Cyclic Pressure Criteria for 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, V eff-asd C 2 x 4 weighing 4.5 lb. +/- 0.25 lb., and with min. length 4 ft. +/- 4-inch 40 ft./sec. or at least 27 mph 35 psf inward and outward 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 (d) Approved Debris Impact Resistant Exterior Wall Assemblies. Wall assemblies constructed in accordance with Table 16-13.7(d) are deemed to comply with § 16-13.7 (b). Table 16-13.7(d) WaIl Assemblies Complying with § 16-13.7(b) Table 16-13.7(d) WaIl Assemblies Complying with § 16-13.7(b) Wall Assemblage 3/4-inch plywood on 2 x 4-inch or larger wood studs spaced at 16 inches, on-center with #8 x 3-inch wood screws at 6 inches on-center. 3/4-inch plywood on 350S162-33 or greater studs spaced at 16 inches on-center with #8 sheet metal screws at 6 inches on-center. 8-1/4-inch cementitious lap siding over 22-gage sheet metal attached to 350S162-33 or greater studs spaced at 24 inches on-center. 8-1/4-inch cementitious lap siding attached to 350S162-33 or greater studs spaced at 24 inches on-center studs with interior 3/4-inch interior plywood sheathing. 8-1/4-inch cementitious lap siding attached to 350S162-33 or greater studs spaced at 24 inches on-center with 1/2-inch interior 22-gage sheet metal composite gypsum wallboard. 8-1/4-inch cementitious lap siding attached to 2 x 4-inch or larger wood studs spaced at 16 inches on-center with 1/2-inch interior 22-gage sheet metal composite gypsum wallboard. 8-1/4-inch cementitious lap siding attached to 2 x 4-inch or larger wood studs spaced at 16 inches on-center with 22-gage sheet metal and 1/2-inch interior gypsum wallboard. Cementitious lap siding attached to 5/8-inch structural plywood on 2 x 4-inch or larger wood studs spaces at 16 inches on-center. Cementitious lap siding attached to 5/8-inch structural plywood on 2 x 4-inch or larger or 363S137-43 or greater steel studs spaced at 16 inches on-center. EFS with 1/2-inch dens-glass gold exterior sheathing on 362S137-43 steel studs spaced at 16 inches on-center and 1/2-inch interior gypsum wallboard 24-gage steel sheet (50 ksi) on girts. Concrete with a thickness of 4 inches with reinforcing. Concrete masonry units with a thickness of 6 inches with partial grouting and reinforcing spaced at 24 inches on-center. Concrete masonry units with a thickness of 8 inches with partial grouting and reinforcing spaced at 24 inches on-center. Interior or exterior wall with laterally braced 2 x 4-inch or larger wood studs with sheathing on either side 22-gage sheet metal. Sheathing must be attached to studs with fasteners at 6 inches (152 mm) on center for edge and field fastening. Door frames and windows must be fastened to structural members on all sides with a maximum fastener spacing of 6 inches, not to exceed 4 inches from the corners, designed in accordance with the pressures of Table 16-13.1 . (e) Approved Debris Impact Resistant Interior Wall Assemblies. Wall assembly construction methods in accordance with Table 16-13.7(e) are deemed to comply with State Building Code Appendix U Section 429.5.2 when sheathing is installed on the debris impacted side of the safe room wall: Table 16-13.7(e) Wall Assembly Methods Complying with State Building Code Appendix U Section 429.5.2 Table 16-13.7(e) Wall Assembly Methods Complying with State Building Code Appendix U Section 429.5.2 Wall Assemblage 1/2-inch plywood on 2 x 4 or larger wood studs spaced at 16 inches on-center with #8 x 3-inch wood screws at 6 inches on-center. 1/2-inch plywood on 350S162-33 or greater metal studs spaced at 16 inches on-center with #8 sheet metal screws at 6 inches on-center. 5/8-inch plywood on 350S162-33 or greater metals studs spaced at 24 inches on-center with #8 sheet metal screws at 6 inches on-center. 1/2-inch interior 22-gage sheet metal composite gypsum wallboard on 2 x 4 or larger wood studs spaced at 16 inches on-center with #8 x 3-inch wood screws at 6 inches on-center. 1/2-inch interior 22-gage sheet metal composite gypsum wallboard on 350S162-33 or larger metal studs spaced at 16 inches on-center with #8 sheet metal screws at 6 inches on-center. Interior doors with 5/8-inch plywood or solid wood panels with three hinges and double latching mechanism. Sheathing must be attached to studs with fasteners at 6 inches (152 mm) on center for edge and field fastening. Door frames and windows must be fastened to structural members on all sides with a maximum fastener spacing of 6 inches and not to exceed 4 inches from the corners, designed in accordance with the pressures of Table 16-13.1 . (f) Approved Debris Impact Resistant Interior Ceiling Assemblies. Wall assembly construction methods in accordance with Table 16-13.7(f) shall be deemed to comply with State Building Code Appendix U Section 429.5.2. Table 16-13.7(f) Wall Assembly Methods Complying with State Building Code Appendix U Section 429.5.2 Wall Assemblage 1/2-inch plywood on either side of ceiling joists spaced at 24 inches on-center with #8 x 3-inch wood screws at 6 inches on-center. 1/2-inch interior 22-gage sheet metal composite gypsum wallboard on either side of ceiling joists spaced at 24 inches on-center with #8 x 3-inch wood screws at 6 inches on-center. Sheathing must be attached to ceiling joists with fasteners at 6 inches (152 mm) on center for edge and field fastening. Door frames and windows must be fastened to structural members on all sides with a maximum fastener spacing of 6 inches and not to exceed 4 inches from the corners, designed in accordance with the pressures of Table 16-13.1 .