04-26-07 Building Codes Appeals Board minutes

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BUILDING PLANNING ~ TABLE R301.2.1.2 WINDBORNE DEBRIS PROTECTION FASTENING SCHEDULE FOR WOOD STRUCTURAL PANELS" b, c, d FASTENER SPACING (inches\ 4 feet < 6 feet < FASTENER Panel span panel span panel span TYPE < 4 feet < 6 feet < 8 feet No.6 Screws 16" 12" 9" No.8 Screws 16" 16" 12" For 81: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound = 4.448N, 1 mile per hour = 0.447 rn/s. a. This table is based on 130 mph wind speeds and a 33-footmean roofheight. b. Fasteners shall be installed at opposing ends of the wood structural panel. Fasteners shall be located a minimum of 1 inch from the edge of the panel. Ie. Fasteners s~~ be long en~ugh to .penetrate through ~e exterior ~~1 cover- ing and a nnmmum of 11/4 mches mto wood wall framing and a lIlII11mum of 11/4 inches into concrete block or concrete, and into steel framing a mini- mum of 3 exposed threads. Fasteners shall be located a minimum of 21/2 inches from the edge of concrete block or concrete. d. Where screws are attached to masonry or masonry/stucco, they shall be attached using vibration-resistant anchors having a minimum ultimate with- drawal capacity of 490 pounds. R301.2.1.3 Wind speed conversion. When referenced documents are based on fastest mile wind speeds, the I three-second gust basic wind speeds, V3s, of Figure R30 1.2(4) shall be converted to fastest mile wind speeds, Vfin' using Table R301.2.1.3. R301.2.1.4 Exposure category. For each wind direction considered, an exposure category that adequately reflects the characteristics of ground surface irregulari- ties shall be determined for the site at which the building or structure is to be constructed. For a site located in the transition zone between categories, the category result- ing in the largest wind forces shall apply. Account shall be taken of variations in ground surface roughness that arise from natural topography and vegetation as well as from constructed features. For any given wind direction, the exposure in which a specific building or other struc- ture is sited shall be assessed as being one of the follow- ing categories: 1. Exposure A. Large city centers with at least 50 per- cent of the buildings having a height in excess of 70 feet (21336 nun). Use of this exposure category shall be limited to those areas for which terrain representative of Exposure A prevails in the upwind direction for a distance of at least 0.5 mile (0.8 Ian) or 10 times the height of the building or other structure, whichever is greater. Possible channeling effects or increased velocity pressures due to the building or structure being located in the wake of adjacent buildings shall be taken into account. 2. Exposure B. Urban and suburban areas, wooded areas, or other terrain with numerous closely spaced obstructions having the size of single-family dwell- ings or larger. Exposure B shall be assumed unless the site meets the definition of another type expo- sure. 3. Exposure C. Open terrain with scattered obstruc- tions, including surface undulations or other irreg- ularities, having heights generally less than 30 feet (9144 nun) extending more than 1,500 feet (457 m) from the building site in any quadrant. This exposure shall also apply to any building located within Exposure B type terrain where the building is directly adjacent. to open areas of Exposure C type terrain in any quadrant for a distance of more than 600 feet (183 m). This category includes flat open country, grasslands and shorelines in hurri- cane prone regions. 4. Exposure D. Flat, unobstructed areas exposed to wind flowing over open water (excluding shore- lines in hurricane prone regions) for a distance of at least 1 mile (1.61 Ian). Shorelines in Exposure D include inland waterways, the Great Lakes and coastal areas of California, Oregon, Washington and Alaska. This exposure shall apply only to those buildings and other structures exposed to the wind coming from over the water. Exposure D extends inland from the shoreline a distance of 1,500 feet (457 m) or 10 times the height of the building or structure, whichever is greater. R301.2.2 Seismic provisions. The seismic provisions of this code shall apply to buildings constructed in Seismic Design Categories C, Do, DI and D2, as determined in accordance with this section. Buildings in Seismic Design Category E shall be designed in accordance with the International Build- ing Code, except when the seismic design category is reclas- sified to a lower seismic design category in accordance with Section R301.2.2.1. Exception: Detached one- and two-family dwellings located in Seismic Design Category C are exempt from the seismic requirements of this code. The weight and irregularity limitations of Section R301.2.2.2 shall apply to buildings in all seismic design categories regulated by the seismic provisions of this code. Buildings in Seismic Design Category C shall be con- structed in accordance with the additional requirements of Section R301.2.2.3. Buildings in Seismic Design Catego-j ries Do, DI and D2 shall be constructed in accordance with.1 the additional requirements of Section R301.2.2.4 .~ ."1 ;1 1 TABLE R301.2.1.3 EQUIVALENT BASIC WIND SPEEDS. -' 3-second gust, V 3s 85 90 100 105 110 120 125 130 140 145 150 160 170 Fastest mile, V fm 71 76 85 90 95 104 109 114 123 128 133 142 152 For 81: 1 mile per hour = 0.447 rn/s. a. Linear interpolation is permitted. 42 2006 INTERNATIONAL RESIDENTIAL copf ~,,;!',