The information herein provides guidelines for complying with the most common wall bracing provisions of Section R602.10 of the International Residential Code and are not representative of all the conditions that may be required. 

Resisting Wind Load

• All buildings must be designed to resist wind load.  Unlike snow load or live load which acts vertically and downward only, wind load acts horizontally and in any direction. 
• The design wind load on a structure is based on the local wind speed which is 115 mph for Commerce City. 
• The structural system of a house is designed to transfer wind load from where it is applied all the way to the ground; this is called “load path.”  Wind load is resisted by the walls parallel to the direction of the wind.  For example, in a simple one-story house, as shown in FIGURE 1, wind against the end wall would cause the roof to move in the direction of the wind, but the movement is resisted by the bracing in the side walls parallel to the wind. 
• This process is similar for houses with multiple floors.  However, in such cases, the walls of the first floor have the added responsibility of resisting the forward movement of all the floors and the roof above. 
• The International Residential Code accounts for the properties and characteristics of wind through the construction requirements in this publication. 

 

FIGURE 1: WIND LOAD APPLIED TO HOUSE 

•  As shown in FIGURE 2, a typical wall will rack due to wind load if no bracing is provided.  When installed in specified locations along a wall, usually in the form of oriented strand board (OSB), bracing prevents this lateral displacement. See FIGURE 3. 
• The code defines a “braced wall panel” as a sheathed, full-height (12-foot maximum) section of wall constructed to resist wind load and placed on a wall in specified lengths and locations.   
• Sheathing types, also called bracing method, are available in various materials and configurations; see Page 7.  A braced wall panel is not required to be constructed with a single sheet of sheathing. Joints are permitted provided vertical joints occur at a stud and horizontal joints are blocked. 

 

FIGURE 2: RACKING DUE TO WIND LOAD 

FIGURE 3: BRACED WALL PANELS 

Braced Wall Lines

• “Braced wall lines” help to ensure proper distribution of bracing throughout your house or addition.  Braced wall lines are imaginary straight lines which represent the centerline of lateral resistance provided by parallel braced wall panels located on or within 4 feet of the braced wall line location.  The amount and location of bracing are derived from the characteristics of each braced wall line.
• You will want to place your braced wall lines strategically using the rules noted herein to ensure the amount of bracing is both economical and safe.  Braced wall lines are required to be located along all the exterior walls of your house or addition such that they intersect with braced wall lines running in the opposite direction at each end.  Braced wall lines are permitted to “float” between actual walls on either side, see BWL-A in FIGURE 4, provided the distance between the actual sheathed walls on either side and the braced wall line are less than or equal to 4 feet.
• Braced wall lines may also need to run through the interior of your house.  For instance, in FIGURE 4, BWL-B, located interior to the house, would be required if the amount of required bracing cannot fit on the actual walls of BWL-A and BWL-C or if the distance between them was greater than 60 feet. 

 

FIGURE 4: PLACEMENT OF BRACED WALL LINES 

Bracing Rules 

The placement and amount of braced wall panels for each braced wall line are required to meet all four of the following rules.

1. Location: Braced wall panels must begin at or within 10 feet of each end of a braced wall line. See FIGURE 5.
2. Spacing: The distance between adjacent braced wall panels cannot exceed 20 feet. See FIGURE 5. 

 

FIGURE 5: BRACED WALL PANELS ON BRACED WALL LINES 

3. Number: Each braced wall line must have at least two braced wall panels.  However, braced wall lines 16 feet long or less are permitted to have one braced wall panel provided it is at least 48 inches long.
4. Amount: The cumulative length of all braced wall panels must be greater than or equal to the required length specified by the code as determined in the steps below.

• Step 1) Calculate the average spacing from the braced wall line you are designing to the next adjacent braced wall lines at each side of each end.  Ensure no value exceeds 60 feet.
• Step 2) Use TABLE 1 below to determine the unadjusted required amount of bracing based on number of stories above, braced wall line spacing, and sheathing method. 

TABLE 1:  MINIMUM REQUIRED LENGTH (FEET) OF BRACING 

• The type, material and configuration of sheathing methods vary.  There are two types of bracing: intermittent, see FIGURE 6, where braced wall panels are placed at required locations only and all other areas are infilled with other material such as insulating foam, and continuous-sheathing, see FIGURE 7, where the entire face of the wall is sheathed, including areas above and below openings.

 

FIGURE 6: INTERMITTENT BRACING 

 

FIGURE 7: CONTINUOUS-SHEATHING 

• In our region, continuous-sheathing is the predominant sheathing type for the exterior, while intermittent is most common for the interior.  TABLE 3 below lists the most common bracing methods and a description of each.  
• Mixing different bracing methods in the same braced wall line is permitted provided the method which generates the highest required length of bracing per TABLE 1 governs the braced wall line design

TABLE 3:  COMMON BRACING METHODS 

TABLE 4: MINIMUM LENGTH OF BRACED WALL PANELS 

 

FIGURE 8: CONTINUOUS-SHEATHING CORNERS 

EXAMPLE: Continuous-Sheathing Panel Length 

In the continuously sheathed braced wall line shown above, find the minimum length of the panel between the window and the door. 

• Use 80 inches as the governing opening height. 
• Use 11 feet as the wall height. 
• Per TABLE 4, the minimum length of the panel = 33 inches. 

In the braced wall line above, calculate the contributing length of the 50-inch, single sided Method GB panel. 

• From TABLE 4, the formula for contributing length (single sided) = 0.5 x actual length. 
• Therefore the contributing length = 50 x 0.5 = 25 inches. 

FIGURE 9: METHOD CS-PF 

• Companies, such as Simpson Strong-Tie, manufacture narrow products made of wood or steel that can fit within your braced wall line and be considered equal to the code-prescribed braced wall panels.  For instance, a 12-inch wide manufactured panel, as shown to the right, can be placed in your braced wall line and be considered the same as a 48-inch braced wall panel.  This can be quite useful if you need a lot of bracing, but have little wall length in which to place it. 

• Acceptable products must be listed with an associated evaluation report by a product evaluating agency such as the International Code Council-Evaluation Service. 

Braced Wall Panel Connections

• Each element resisting horizontal forces in your house or addition needs to be able to support the applied wind load and pass it on to the next bracing element along the load path.  This includes where braced wall panels connect to roof construction, floor construction or stem walls.
• At the roof eave, blocking between the rafter or truss framing is required at braced wall panel locations when dimension D, as shown in FIGURE 10, is greater than 9¼ inches.  For heights up to 15¼ inches, solid blocking is permitted as shown in FIGURE 11.  For heights greater than 15¼ inches and up to 48 inches, provide vertical panels as shown in FIGURE 12.  Heights greater than 48 inches require an engineered design.
• Added framing or blocking is required below an interior braced wall panel when attached to floor construction as shown in FIGURE 13.   
• When a braced wall panel is 48 inches long or less and supported by a masonry or concrete stem wall, reinforcement in accordance with FIGURE 14 must be provided. 

FIGURE 10: DISTANCE, D 

FIGURE 11: SOLID 2x BLOCKING 

FIGURE 12: VERTICAL BLOCKING PANELS 

FIGURE 13: INTERIOR BRACED WALL PANEL AT FRAMING 

FIGURE 14: MASONRY STEM WALLS SUPPORTING BRACED WALL PANELS 

Engineered Design

• If you wish to deviate from the prescriptive code requirements, then your house or addition, or a portion thereof, must be designed by a Colorado licensed professional engineer.  Use the following criteria to ensure a successful submission.
• Determine the wind load on your house or addition using the ASCE-7 standard.  For Commerce City, the ultimate design wind speed is 115 mph with Wind Exposure Category B.  Determine shear wall or diaphragm compliance using the “Special Design Provisions for Wind and Seismic” standard by the American Wood Council.  Accepted engineering practice shall be employed in the submitted calculations which must include the following:
  • A detailed wind load determination.
  • A detailed design of the shear walls and/or diaphragms.
  • Minimum aspect ratio of shear walls and/or diaphragms.
  • Specification of the sheathing thickness, nail sizes and nailing pattern.
  • A detailed analysis of all connections along the lateral load path. 
  • The original signature and seal of the professional engineer. 
• Calculations which do not meet these requirements will not be approved during the permit application and plan review process.
• Pre-engineered steel moment frames, as shown below, from companies such as Simpson Strong-Tie are cost-effective alternatives to a fully engineered design.  Each model is pre-engineered with a maximum load capacity outlined in the manufacturer’s catalog.
• While you will still need to employ a licensed engineer, he or she will simply need to calculate the amount of wind load delivered to the frame and then choose the correct model from the manufacturer based on its capacity. 

• Pre-engineered moment frames are particularly useful for lengths of wall with large openings and high amounts of load, such as the first floor of a three-story townhouse. 

Submission Requirements 

• All plans submitted to the county for permit application and plan review must have all braced wall lines, braced wall panels and method(s) clearly identified. Plans will not be approved otherwise. 
• An interactive worksheet to assist you with designing your wall bracing is available here. It is recommended that you submit the corresponding worksheets with your plans.   
• When submitting plans for a house that utilizes a proprietary system or an engineered design, the related evaluation report, manufacturer’s catalog and/or calculations must be attached to the plans.   
• The drawings must also include comprehensive details outlining the construction requirements of the diaphragms and shear walls. These detail sheets must also bear the original signature and seal of the responsible professional engineer.