Section 1609 Wind Loads
Wind loads on every building or structure shall be determined in accordance with Chapters 26 to 30 of ASCE 7. The type of opening protection required, the basic design wind speed, V, and the exposure category for a site is permitted to be determined in accordance with Section 1609 or ASCE 7. Wind shall be assumed to come from any horizontal direction and wind pressures shall be assumed to act normal to the surface considered.
- Subject to the limitations of Section 1609.1.1.1, the provisions of ICC 600 shall be permitted for applicable Group R-2 and R-3 buildings.
- Subject to the limitations of Section 1609.1.1.1, residential structures using the provisions of AWC WFCM.
- Subject to the limitations of Section 1609.1.1.1, residential structures using the provisions of AISI S230.
- Designs using NAAMM FP 1001.
- Designs using TIA-222 for antenna-supporting structures and antennas, provided that the horizontal extent of Topographic Category 2 escarpments in Section 220.127.116.11 of TIA-222 shall be 16 times the height of the escarpment.
- Wind tunnel tests in accordance with ASCE 49 and Sections 31.4 and 31.5 of ASCE 7.
The wind speeds in Figures 1609.3(1) through 1609.3(8) are basic design wind speeds, V, and shall be converted in accordance with Section 1609.3.1 to allowable stress design wind speeds, Vasd, when the provisions of the standards referenced in Exceptions 4 and 5 are used.
The provisions of ICC 600 are applicable only to buildings located within Exposure B or C as defined in Section 1609.4. The provisions of ICC 600, AWC WFCM and AISI S230 shall not apply to buildings sited on the upper half of an isolated hill, ridge or escarpment meeting all of the following conditions:
- The hill, ridge or escarpment is 60 feet (18 288 mm) or higher if located in Exposure B or 30 feet (9144 mm) or higher if located in Exposure C.
- The maximum average slope of the hill exceeds 10 percent.
- The hill, ridge or escarpment is unobstructed upwind by other such topographic features for a distance from the high point of 50 times the height of the hill or 2 miles (3.22 km), whichever is greater.
In windborne debris regions, glazing in buildings shall be impact resistant or protected with an impact-resistant covering meeting the requirements of an approved impact-resistant standard or ASTM E1996 and ASTM E1886 referenced herein as follows:
- Glazed openings located within 30 feet (9144 mm) of grade shall meet the requirements of the large missile test of ASTM E1996.
- Glazed openings located more than 30 feet (9144 mm) above grade shall meet the provisions of the small missile test of ASTM E1996.
- Wood structural panels with a minimum thickness of 7/16 inch (11.1 mm) and maximum panel span of 8 feet (2438 mm) shall be permitted for opening protection in buildings with a mean roof height of 33 feet (10 058 mm) or less that are classified as a Group R-3 or R-4 occupancy. Panels shall be precut so that they shall be attached to the framing surrounding the opening containing the product with the glazed opening. Panels shall be predrilled as required for the anchorage method and shall be secured with the attachment hardware provided. Attachments shall be designed to resist the components and cladding loads determined in accordance with the provisions of ASCE 7, with corrosion-resistant attachment hardware provided and anchors permanently installed on the building. Attachment in accordance with Table 1609.2 with corrosion-resistant attachment hardware provided and anchors permanently installed on the building is permitted for buildings with a mean roof height of 45 feet (13 716 mm) or less where Vasd determined in accordance with Section 1609.3.1 does not exceed 140 mph (63 m/s).
- Glazing in Risk Category I buildings, including greenhouses that are occupied for growing plants on a production or research basis, without public access shall be permitted to be unprotected.
- Glazing in Risk Category II, III or IV buildings located over 60 feet (18 288 mm) above the ground and over 30 feet (9144 mm) above aggregate surface roofs located within 1,500 feet (458 m) of the building shall be permitted to be unprotected.
WINDBORNE DEBRIS PROTECTION FASTENING SCHEDULE FOR WOOD STRUCTURAL PANELSa, b, c, d
|FASTENER TYPE||FASTENER SPACING (inches)|
|Panel Span |
≤ 4 feet
|4 feet < Panel |
Span ≤ 6 feet
|6 feet < Panel |
≤ Span 8 feet
|No. 8 wood-screw-based anchor with 2-inch embedment length||16||10||8|
|No. 10 wood-screw-based anchor with 2-inch embedment length||16||12||9|
|1/4-inch diameter lag-screw-based anchor with 2-inch embedment length||16||16||16|
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound = 4.448 N, 1 mile per hour = 0.447 m/s.
- This table is based on 140 mph wind speeds and a 45-foot mean roof height.
- Fasteners shall be installed at opposing ends of the wood structural panel. Fasteners shall be located not less than 1 inch from the edge of the panel.
- Anchors shall penetrate through the exterior wall covering with an embedment length of 2 inches minimum into the building frame. Fasteners shall be located not less than 21/2 inches from the edge of concrete block or concrete.
- Where panels are attached to masonry or masonry/stucco, they shall be attached using vibration-resistant anchors having a minimum ultimate withdrawal capacity of 1,500 pounds.
The text of Section 6.2.2 of ASTM E1996 shall be substituted as follows:
6.2.2 Unless otherwise specified, select the wind zone based on the basic design wind speed, V, as follows:
18.104.22.168 Wind Zone 1—130 mph ≤ basic design wind speed, V < 140 mph.
22.214.171.124 Wind Zone 2—140 mph ≤ basic design wind speed, V < 150 mph at greater than one mile (1.6 km) from the coastline. The coastline shall be measured from the mean high water mark.
126.96.36.199 Wind Zone 3—150 mph (58 m/s) ≤ basic design wind speed, V ≤ 160 mph (63 m/s), or 140 mph (54 m/s) ≤ basic design wind speed, V ≤ 160 mph (63 m/s) and within one mile (1.6 km) of the coastline. The coastline shall be measured from the mean high water mark.
188.8.131.52 Wind Zone 4— basic design wind speed, V > 160 mph (63 m/s).