Oklahoma Administrative Code
Title 748 - Oklahoma Uniform Building Code Commission
Chapter 20 - Adopted Codes
Subchapter 6 - IRC[®] 2018
Section 748:20-6-53 - Appendix X, Residential Tornado Provisions

(1) Section X101.1 General. This section has been added to clarify the provisions shall be applicable for new construction. This section has been added to read: X101.1 General. These provisions shall be applicable for new construction where residential tornado provisions are required. This appendix provides prescriptive based requirements for construction of a residential structure meeting or exceeding a 135-mph wind event corresponding to an EF-2 tornado rating. The single most important objective in protecting a structure against high wind is achieving a continuous load path from the roof to the foundation. Based on the findings of studies and failures associated with various construction types, a group of 11 building practices (each associated with a different aspect of the structure) are summarized in this section.

(2) Section X101.2 Application. This section has been added to clarify the administrative provisions of this appendix are applicable in the administrative and building planning and construction requirements in Chapters 1 through 10 of this code. The section has been added to read: X101.2 Application. In addition to the general administration requirements of Chapter 1, the administrative provisions of this appendix shall also apply to the building planning and construction requirements of Chapters 1 through 10.

(3) Section X101.3 Wind design criteria. This section has been added to clarify that if Section R301.2.1 is modified, the buildings and portions thereof shall be constructed in accordance with the code and the ultimate wind speed design of 135 mph. This section has been added to read: X101.3 Wind design criteria. Modifying section R301.2.1 buildings and portions thereof shall be constructed in accordance with the wind provisions of this code using the ultimate design wind speed 135 mph.

(4) Section X101.4 Lumber sheathing. This section has been added to address the permitted forms of lumber sheathing. This section has been added to read: X101.4 Lumber sheathing. Only OSB or plywood sheathing is permitted. Dimensional lumber sheathing may not be used. Allowable spans and attachment for lumber used as roof or exterior wall sheathing shall conform to the following:

(5) Section X101.5 Ceiling joist and rafter connections. This section has been added to require ceiling joists and rafters to be nailed to each other in a manner to achieve a connection that can transfer a 500-pound force in both compression and tension across the connections. This section has been added to read: X101.5 Ceiling joist and rafter connections. In addition to the provisions of Chapter 8, ceiling joists and rafters shall be nailed to each other in a manner to achieve a connection that can transfer a 500-pound force in both compression and tension across the connection.

(6) Section X101.6 Rafter uplift resistance. This section has been added to require individual rafters to be attached to supporting wall assemblies by connections capable of resisting uplift forces of 500 pounds. This section has been added to read: X101.6 Rafter uplift resistance. Individual rafters shall be attached to supporting wall assemblies by connections capable of resisting uplift forces of 500 pounds.

(7) Section X101.7 Gable end walls. This section has been added to clarify connections and sheathing for gable end walls. This section has been added to read: X101.7 Gable end walls. Gable end walls will be sheathed per X101.4 and will have connections to both a.) supporting wall assemblies and b.) roof framing by connections capable of resisting uplift forces of 500 pounds in both compression and tension across the connection.

(8) Section X101.8 Exterior wall bracing. This section has been added to clarify sheathing methods to be utilized to brace exterior walls and prohibit intermittent bracing on exterior walls. This section has been added to read: X101.8 Exterior wall bracing. Only continuous sheathing methods per R602.10.4.2 may be used to brace exterior walls. Frame garage doors using the sheathed portal frame method CS-PF. Lumber sheathing and attachment per X101.4. Any form of intermittent bracing is not allowed on an exterior wall. Intermittent bracing may only be used for interior braced wall lines.

(9) Section X101.9 Multi story construction. This section has been added to require nailing upper and lower story wall sheathing to a common rim board. This section has been added to read: X101.9 Multi story construction. Nail upper and lower story wall sheathing to common rim board in order to maintain continuity between stories.

(10) Section X101.10 Wood floor above crawl space construction. This section has been added to require extending structural wood sheathing to lap the sill plate. This section has been added to read: X101.10 Wood floor above crawl space construction. Extend structural wood sheathing to lap the sill plate. Nail to sill plate at 4 inches on center along the edges. Nail to rim board if present with 8d ring shank (0.131 inch x 2.5 inch) or 10d (0.148 inch x 3 inch) nails at 4 inches on center along both the top and bottom edges of the rim board.

(11) Section X101.11 Garage Doors. This section has been added to require garage doors to be rated for 135 mile per hour winds. This section has been added to read: X101.11 Garage Doors. Garage doors are to be wind rated to 135 mph.