I Level Wall Bracing

8/4/2019 I Level Wall Bracing

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7800 E. Orchard Rd., Suite 200,Greenwood Village, CO 80111

Prescriptive Code ProvisionsHow to apply prescriptive code provisions toidentify braced wall lines and select braced wallpanel types and locations

Based on

IRC 2006

WaallllBBraacciinng 4011


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Theinformationpresentedinthisdocumentisbasedonthe2006IRC("code")wallbracingsectionR602.10andisintendedtobeusedasaguidelineforspecifyingwallbracinginresidentialstructures. Whileeveryattempthasbeenmadetoensuretheinformationhereinisaccurateandincompliancewiththecode,itisnotintendedtosupersedeorreplacethecode. Theuserofthisinformationshouldalwaysrefertothecodeprovisionsandworkwiththeirlocalbuildingofficialtoensurebracingsolutionsarecodecompliant.


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Wall Bracing 401 1

Table of ContentsObjectives and Overview .......................................................... 4Section 1. About Lateral Forces ............................................. 7

Whats a Lateral Force? ............................................................................................................................ 7Effects of Lateral Loads on Structures ...................................................................................................... 7Lateral Force Resisting System ................................................................................................................ 8

Section 2. About Braced Walls ............................................. 11Braced Walls vs. Shear Walls ..................................................................................... 11Braced Walls and Load ............................................................................................... 11

Forces on a Braced Wall Panel ............................................................................................................... 12Resistance to Lateral Forces and Prescriptive Solutions ........................................................................ 12Lateral Wind and Seismic Forces............................................................................................................ 13

Section 3.

Braced Wall Lines and Braced Wall Panels .......... 15

Braced Wall Lines ................................................................................................................................... 16Braced Wall Panels ................................................................................................................................. 16

Basic Rules for Identifying Braced Wall Lines ......................................................... 17Determining the Length of Braced Wall Line ........................................................................................... 18Allowable Offsets in a Braced Wall Line .................................................................................................. 20Distance between Braced Wall Lines ...................................................................................................... 22

Prescriptive-Braced Wall Panel Solutions Using IRC Methods .............................. 26IRC Methods ........................................................................................................................................... 26How to Use Method 3 and Method 5 ....................................................................................................... 30Deciding which Method to Use ................................................................................................................ 32

Basic Rules for Specifying Braced Wall Panels ....................................................... 33Minimum Percentages for Bracing .......................................................................................................... 33Location and Spacing of Braced Wall Panels ......................................................................................... 35Width of Braced Panel ............................................................................................................................ 36Types of Braced Wall Panels and Alternative Approaches ..................................................................... 37

Tables to Assist in Prescriptive Solutions ................................................................ 42Section 4. Procedure for Specifying Prescriptive Solutions .. 47Appendices ............................................................................ 60

Appendix A Hints for Designers ............................................................................. 60Appendix B 50-ft Braced-line Exception ................................................................ 61Appendix C Suggestions for Typical General Notes on Plans ............................ 62Appendix D IRC Comparison Matrix ....................................................................... 63

Answers to and Quick Checks and Skill Checks ...................... 66


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Wall Bracing 401 2

Table of FiguresFigure 1: Effects of Lateral Loads on Structures ................................................................. 7Figure 2: LFRS .................................................................................................................... 8Figure 3: Roof and Floor Diaphragm Forces ....................................................................... 9Figure 4: Resisting Forces .................................................................................................. 9Figure 5: Braced Walls Transfer Load .............................................................................. 11Figure 6: Forces on a Braced Wall Panel ......................................................................... 12Figure 7: Wall Space and Braced Panels ......................................................................... 12Figure 8: ASCE 7-05 Wind Speed Map ............................................................................ 13Figure 9: Seismic Design Categories ................................................................................ 14Figure 10: Braced Wall Line containing Braced Wall Panels ............................................ 15Figure 11: Braced Wall Line Examples ............................................................................. 16Figure 12: Longitudinal and Transverse ............................................................................ 17Figure 13: Exterior Braced Wall Lines............................................................................... 18Figure 14: Interior Braced Wall Line .................................................................................. 19Figure 15: Direct Vertical................................................................................................... 19Figure 16: Allowable Offsets ............................................................................................. 20Figure 17: Distance between Braced Wall Lines .............................................................. 22Figure 18: Distance between Braced Wall Lines (Cont.) .................................................. 24Figure 19: Distance between Braced Wall Lines (Cont.) .................................................. 25Figure 20: Method 3 Braced Panel ................................................................................... 30Figure 21: Options Using Method 3 .................................................................................. 30Figure 22: Location and Spacing of Braced Wall Panels .................................................. 35Figure 23: Braced Wall Diagrams ..................................................................................... 36Figure 24: Label for Continuous Sheathing ....................................................................... 37Figure 25: Alternate-Braced Wall Panels .......................................................................... 38Figure 26: Alternate-Braced Panel Label .......................................................................... 38Figure 27: Schematic of 2007 IRC Supplement - Field-built Single and Double PortalFrame ................................................................................................................................ 39Figure 28: Prefabricated Portal ......................................................................................... 40Figure 30: 12" Return ........................................................................................................ 60

Table of TablesTable 1: Simplified Version of IRC 2006 Table R602.10.1 ................................................ 34Table 2: Method 3: Braced Panel Systems, as Required for Each Wall ........................... 42Table 3: Method 3: Continuous Sheathing - Fully Sheathed Exterior Walls ..................... 43 Table 4: Calculating Braced Wall Panel Percentages ....................................................... 44


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Wall Bracing 401 3

Prescriptive Wall Bracing 401 - IntroductionWelcome to Prescriptive Wall Bracing 401!

This manual provides in-depth training on Prescriptive Wall Bracing.

The International Residential Code (IRC) requires that walls are braced, to resist lateralforces. Bracing a wall requires braced wall panelsto be included into a braced wall line.

Braced wall design can be either designed or prescriptive.

A Designed Solution is the design of a structure that is specific to the conditions of thatstructure, done by a design professional.

A Prescriptive Solution is a specification of products or construction practices that can beaccomplished by following a particular set of rules. In the case of wall bracing, these rulesare outlined in the IRC Section 602.10.

This course, as you may have guessed, has been created to show you more precisely

what the 2006 IRC requires concerning prescriptivewall bracing and how to meet theserequirements. In Appendix D, youll also find information on variations in requirements inthe 2000 and 2003 IRC, and the 2007 Supplement to the 2006 IRC.


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Wall Bracing 401 4

Objectives and OverviewObjectives

Prescriptive Wall Bracing 401 has only one primary learning objective: In this course, youwill learn how to provide braced wall lines to resist wind or seismic loads.

Knowledge and Skills

In order to accomplish this objective, you will need to acquire new knowledge and skills.This course will provide you with the knowledge and skills to:

Identify and specify braced lines of resistance for each floor level.

Determine the IRC Method to use. You will apply prescriptive code provisions

using one or more of the methods listed in the International Residential Code

(IRC) for lateral bracing to a structure in seismic design categories A D2 and

where wind speeds are less than 110 mph.*

Determine the percentage of the wall that must be braced.

Determine the location and spacing of these panels.

Provide alternate bracedwall panels solutions where necessary.


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Wall Bracing 401 5

Overview of This Module

Terms and Definitions

Braced Wall: A wall prescribedusing the International Residential Code (IRC) toresist lateral loads. It behaves similarly to a shear wall. Unlike the shearwall, a braced wall does not necessarily have hold downs.

Braced wall line: A wall containing a series of braced wall panels in a single-story homeconstructed in accordance with Section R602.10.

Braced wallpanels:

A section of a wall that is braced in order to resist lateral loads. In thiscourse, panels are limited to structural wood sheathing (e.g., OSB orplywood), interior gypsum wallboard, prefabricated panels, or codealternate-braced panels (2006 International Residential Code [IRC] and2007 IRC Supplement).

Designedsolution:

Design of a structure that is specific to the conditions of that structure,done by a design professional of record.

Lateral: Something that is situated on, directed toward, of coming from the side.

Lateral ForceResisting

System (LFRS):

The combination of stud wall framing, floor and roof diaphragms,collectors, shear walls and/or portal frames that provide support andstability for the structure to resist seismic or high wind forces.

Lateral forces: Forces caused by loads acting horizontally on the structure - usuallywind or seismic forces.

Longitudinal: The direction of the walls parallel to the long direction of the home.

Offset: The perpendicular distance between two parallel lines.

Prescriptivesolution:

The specification of products or construction practices that can beaccomplished by following a particular set of rules. In the case of wall

bracing, these rules are outlined in the IRC Section 602.10.Shear Wall: A wall that is designedto resist lateral loads. Shear walls are connected

with hold downs. Their detailing is explained thoroughly in theInternational Building Code (IBC).

Sliding: The effect from lateral forces that cause the structure to slide off thefoundation.

Transverse: The direction of the walls parallel to the short direction of the building.

Uplift andOverturning:

The effect from lateral forces that cause the structure or a wall elementto tip or overturn.


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Wall Bracing 401 6

Important Points

1. The two most important effects of lateral forceson a structure that must be resistedare:

Uplift and Overturning

Shearing

2. The procedure youll learn in this course is for:

Seismic design categories A D2

Wind speeds of110 mph or less

3. Design considerations for wall bracing include the following:

Distance from an openingto the end of a braced wall line.

Offsetsof walls within the braced wall line

Distance between braced wall panels and braced wall lines

Wall space(width) for bracing

Size of an openingnext to a braced wall panel

4. Braced Wall Panels discussed in this course include:

Panels built with structural wood sheathing (OSB or plywood)

Panels built with interior gypsum wallboard

IRC alternate-braced panels

Prefabricated panels

5. While there are many considerations to make when designing a braced wall system,the basic approach is to follow these steps:1. Identifypotential braced wall lines.

2. Determine which method(from the IRC) to use.

3. Determine the percentageof the overall length of the braced wall line that thebraced wall panels must comprise.

4. Determine the locations and widths available for braced wall panels within thebraced wall line.

5. Suggest alternate panels or portals where necessary.

6. General notes and detailsfor wind and seismic bracing should include:

Wind speed

Seismic design category

Type of bracing Location of braced panels on plans


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Wall Bracing 401 8

Lateral Force Resisting System

Now that you know how lateral forces work, take a look at how a typical structure isdesigned to resist them using a Lateral Force Resisting System.

A Lateral Force Resisting System (LFRS) is a system of floor, roof, and wall framing

elements that, in combination, resist lateral forces (Figure 2).

Stud walls, acting like vertical joists, deflect under the pressure of the wind force andtransfer the lateral forces to the diaphragm above and to the foundation below (Figure 2).

Figure 2: LFRS

Diaphragm spansbetween braced or

shear walls


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Wall Bracing 401 9

Floor and Roof Diaphragms

Floor or roof decks are diaphragmswhich act as deep beams spanning between walls,transferring load into the wall lines where the diaphragm connects to them. As lateral loadis applied to the stud walls perpendicular to it, the forces caused by the load transfer fromthe perpendicular wall into the diaphragms. The forces then transferfrom the diaphragms

to the shear wallor to a braced wall linethat runs parallel to the lateral force (Figure 3).

Figure 3: Roof and Floor Diaphragm Forces

Walls

The most common LFRS is a braced wall systemthat relies on the wallsto resist the effects

overturning and sliding due to high wind orseismic forces.

So how must the walls be constructed in order toresist these forces? Often, this can be a difficultproblem to solve and may require a designedsolution.

Fortunately, however, in most cases, there areseveral prescriptive solutions that accomplish thetask adequately.

Figure 4: Resisting Forces

Prescriptive solutions are acceptable for most applications where wind speed is less than110 mph, and the Seismic Design Category is A, B, C, and for many applications inSeismic Design Category D0 D2.

These solutions often involve integrating braced wall panels into the wall system. Youlllearn about these in the following section.

Forces transferfromthe Diaphragm into

Braced Walls

Perpendicular Studstransfer forces intotheDiaphragm

Shear Wall or

Braced WallLine

Foundation

Lateral load is appliedto the perpendicular

stud wall

Diaphragm

roof or floor

ShearWall or

BracedWall

Foundation

Bracedwalls mustresist lateralforces


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Wall Bracing 401 10

Quick Check

Answer the following questions to check your knowledge about lateral loads.

1. A lateral load is most often caused by

Wind or snow Wind or earthquake

Earthquake or fire

2. The two effects of lateral forces that a building must resist are

Uplift and compression

Overturning and sliding

Shearing and seismic

3. How does lateral load on the diaphragm affect the walls in an LFRS?

Lateral load perpendicular to the wall studs is transferred to the diaphragm,which transfers this load into the walls parallel to the wind or seismic load.

Lateral load from the diaphragm causes walls to move inward toward thecenter of the building.

The diaphragm resists most of the lateral load, relieving the walls from beingsubjected to these loads.

(Answers on page 66.)


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Wall Bracing 401 11

Section 2. About Braced WallsBraced Walls vs. Shear Walls

Youve learned that lateral loads applied a structure must be resisted by shear walls or by

braced walls. Both of these wall types include the stud framing, sheathing, nailing, top andbottom plates, and connection hardware to resist overturning and sliding forces. Whetherthe wall is a shear wall or a braced wall, its purpose is to transfer shear load. Its ability totransfer shear load depends on the height to width ratio of the wall.

You may find that you hear each of these terms often; they may seem to be referring to thesame thing. Conceptually speaking, they are the same thing; both provide lateral stabilityto a structure. The primary difference is this:

A shear wall is a wall that has established design values to allow products to be designedto resist lateral loads. Shear walls are connected with hold downs. Their detailing isexplained thoroughly in the International Building Code (IBC).

A braced wall is a wall prescribedusing the International Residential Code (IRC) to resistlateral loads. It behaves similarly to a shear wall. But unlike the shear wall, it does not haveestablished design values, and is not necessarily connected with hold downs.

Although a braced wall does not have established design values, it is still appropriate forcertain structures. Such structures meet certain size and use limitations, which allow themto be constructed using prescriptive solutions.

A prescribed solution, by definition, does not have calculated loads. Since there areoccasions where structures in prescriptive markets require designed solutions, it ispossible for a single building to contain both shear walls and braced panels.

As this course is concerned with prescribed solutions only, youll be learning about bracedwalls.

Braced Walls and Load

Braced walls transfer the load from thefloor or roof diaphragm above into thefoundation below (Figure 5).

It is not always necessary to brace everypart of every wall in a structure in orderfor it to be able to resist lateral forces.Often, only sections of the wall need tobe braced.

A braced wall panel is a sectionof thewall that is braced.

Figure 5: Braced Walls Transfer Load

BracedWall

Deflection of Braced Wall


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Wall Bracing 401 12

Forces on a Braced Wall Panel

All braced wall panels, regardless of the material, must resist the same kinds of forces(Figure 6). These forces include:

Shear force from the

diaphragm Compression

Uplift (tension)

Figure 6: Forces on a Braced Wall Panel

Resistance to Lateral Forces and Prescriptive Solutions

When a building is constructed using conventional construction practices according to IRCguidelines, these forces are usually resisted adequately.

For example:

Shearis resisted with anchor bolts.

Compressionis resisted with a typical three-stud corner.

Upliftis resisted with anchor bolts, by adjacent walls, and by the dead load of thestructure from above.

As a result, special detailing for shear, compression, and uplift is generally not necessaryin a prescriptive home.

However, even in prescriptive construction, a braced wall panel must be strong enough toresist the lateral loads. Generally speaking, widerwall panels are stronger than narrowerpanels that are constructed with the same materials and construction techniques. As youllsee, the braced wall requirements outlined in the IRC dictate how wide a panel must beand where it may be located within the wallline. For example, wall spaces with openingscannot be used to resist lateral load.

In order to meet these requirements, theuninterrupted space (wall without openings)must be wide enough to contain the propersize panel. Section 3 discusses specificrequirements outlined in the IRC regardingwall bracing and the selection of braced wallpanels.

Figure 7: Wall Space andBraced Panels

Uninterrupted space must bewide enough

Openings cannot resist lateral loads

Dead load of thestructure resists u lift

Braced WallPanel

Foundation orwall below

Shear force fromDiaphragm

Uplift

Compression

Resistingshearing force


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Wall Bracing 401 13

Lateral Wind and Seismic Forces

Expected wind and seismic (earthquake) forces vary by area across the country. Eachlocal jurisdiction establishes what criteria are appropriate for determining expected windand seismic forces in their region. These values are based on historic data of wind speedand seismic activity, and on activity in areas that are similar in topography and geology.

National maps created by the United States Geological Survey (USGS) and the AmericanSociety of Civil Engineers (ASCE) show design earthquake intensity and wind speedsacross the country. Your local jurisdiction can give you specific information on the windspeed and seismic design category for your area. To find this information, contact yourlocal building official.

Below are the general wind and seismic design category maps for the continental UnitedStates from ASCE and the USGS.

Figure 8: ASCE 7-05 Wind Speed MapReproduced with permission of ASCE

Values indicate 3 sec windgust speeds in mph per2006 IRC R301.2 (4)


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Wall Bracing 401 20

Allowable Offsets in a Braced Wall Line

Braced wall lines do not have to be continuous for their full length. Often,individual walls are out-of-plane with one another, oroffset.

The offset is the perpendicular distance between two parallel lines.

The IRC allows offsets to either side of a braced wall line according to thefollowing criteria:

4 maximum offset from one part of a braced wall to another.

8 maximum total offset.

Figure 16: Allowable Offsets

The 50 long braced wall lines in Figure 16 are considered equivalent to one another; bothcases are within the code-allowed offsets. The bracing length required for the structure onthe left is equal to that required on the right side.

If offsets are greater than those shown, consider using a different wall or set of walls for abraced wall line. In some cases, there may be no interior walls that meet these criteria. Insuch cases, walls must be moved or engineering may be required.

offset

Direction of Lateral

Force

Braced wall linecontaining

braced panels

17-0

15-0

18-0

4-0

8-0 max

Braced wallline containingbraced panels

Designated 50-ftBraced Wall Line

Direction of LateralForce


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Wall Bracing 401 27

Method 2: Diagonal Wood Boards

(attached to studs)

Advantage Disadvantages

Attractive exteriorfinish

Labor intensive

Expensive

Not commonly used

Method 3: Wood Structural PanelSheathing (i.e., OSB or Plywood)

(attached to studs)

Advantages Disadvantages

Widely acceptedpractice.

Most flexible solution:easier to meet coderequirements,especially indifficult-to-bracesituations.

The IRC is ambivalenttoward panelorientation. Verticaland horizontal

applications aretreated equally forprescriptivesolutions.

Can be more complexto insulate. Rigidinsulation board ismixed withnon-insulated woodpanels creatingpotential coldspots.

May have to create animpermeablewaterproof barrier atexterior (i.e., paint or

house wrap)

Method 4: Structural FiberboardSheathing (i.e., ProprietarySynthetic Materials)

(attached to studs)


Better R-valuedepending onmanufacturer

Possible cost savings

Limited to 4 widthsminimum

Limits window and

door sizes/locations


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Wall Bracing 401 28

Method 5: Gypsum Sheathing

(attached to studs)


Potentially eliminatesexterior bracing

May allow for moreexterior insulation

Will already be used;thus, a benefit.

Special detailing ornailing is not required

48 minimum walllength for interiorwalls with gypsumon both sides.

96 min. wall lengthfor typical exteriorwalls (with gypsumon one side).

Framing chases andother typicallynon-drywalled wallsmay limit or createframing difficulties.

Very low strength if it

gets wet

Method 6: Particleboard Sheathing

(attached to studs)


Another way to getbracing

Not a commontechnique


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Wall Bracing 401 30

How to Use Method 3 and Method 5

For the purpose of this course, only Methods 3 and 5 are considered for specifying bracedwall panels. These methods are the frequently specified in construction practice. Here aresome important points to remember about each:

Method 3

Method 3 is a common method for bracing exteriorwalls. This method of constructingbraced wall panels involves nailing a wood-structural panel (such as OSB) to one side ofthe studs. Method 3 requires this sheathing to be at least 5/16 thick for 16 stud spacing or3/8 thick for 24 stud spacing.

Braced Panel Systems vs. Continuous Sheathing

When the wood-structural sheathing is applied tofull-height studs, the wall section becomes a bracedpanel that meets IRC requirements for Method 3,provided the sheathed wall section is wide enough. In

this course, you will learn the specific criteria a sheathedwall section must meet in order to be considered abraced panel.

Method 3 is used with two common constructionpractices: braced panel systems and continuouslysheathed walls.

Figure 20: Method 3 Braced Panel

A braced panel system incorporates braced panelsintermittentlythroughout the braced wall line.

Continuous sheathing is a construction practice that involves

attaching wood-structural sheathing to all sectionsof theexterior walls. Using this construction practice requires Method3. No other IRC method is accepted.

As mentioned earlier, the IRC considers a wall to be bracedwhen a specific percentage of the braced wall lines lengthcontains braced wall panels. It may seem as though acontinuously sheathed wall is 100% braced. After all, whensheathing is applied to full-height studs, the wall sectionbecomes a braced panel.

However, continuous sheathing does notguarantee that the

walls meet IRC bracing requirements! Even walls that arecontinuously sheathed must be examined to verify that theyare sufficiently braced.

Figure 21: Options Using Method 3

OSB nailed toone side of studs

Braced PanelSystem

Continuous

Sheathin


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Wall Bracing 401 31

One important thing to remember is that a braced wall panel must be constructed withfull-height studs. Whether sheathed or not, any part of the wall that contains an opening(window, door, etc.) cannot be considered a braced wall panel.

Another important thing to remember is that depending on the height of the wall, certainnarrow sections of a continuously sheathed wall are not considered to be braced. In orderto be considered as bracing, the wall section must be:

24 wide for an 8 wall.

27 wide for a 9 wall.

30 wide for a 10 wall.

In summary, here are the important things to remember concerning Method 3:

Method 3 is commonly used forexteriorbraced wall lines.

If a fully sheathed home is desired (or needed), only Method 3 is accepted. TheIRC refers to full sheathing as continuous sheathing.

Method 3 can be used continuously or as individual braced panels. But continuous

sheathing does notguarantee that the walls meet IRC bracing requirements! Method 3 requires wood structural panel sheathing at least 5/16 thick for 16 stud

spacing or 3/8 thick for 24 stud spacing. Sheathing is required on one side of thestuds.


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Wall Bracing 401 32

Method 5

Just like with Method 3, braced wall panels constructed according to Method 5 must beconstructed from full-height studs in order to be considered braced panels. Walls sectionscontaining openings cannot act as braced wall panels.

Here are the important things to remember about using Method 5:

Method 5 is commonly used forinteriorbraced wall lines.

Because braced lines must be no more than 35 apart, interior walls are frequentlyneeded as braced wall lines.

This method requires gypsum to be attached to the studs with nails at7 on-center. Blocking is required along the panel edges nailed horizontally at7 on-center.

If gypsum is attached on one side of the studs, the wall section must be at least96 in order to be considered a braced panel.

If gypsum is attached on two sides of the studs the wall section must be at least

48 in order to be considered a braced panel.

Deciding which Method to Use

Now that you understand how the IRC categorizes the construction methods of bracedwall panels, you can assign one of these methods to each of the braced wall lines youhave identified. The IRC indicates different criteria for wall bracing depending on themethod you use. You must specify braced wall panels that meet the IRC criteria for themethod you have chosen.

Choosing a method is usually done according to these simple guidelines:

In most cases, you will use either Method 3 or Method 5 to figure wall bracingrequirements; Method 3 for exterior walls, Method 5 for interior walls.

Exterior walls can be constructed as braced panel systems or as continuouslysheathed walls. In either case, the calculations for determining bracingrequirements using Method 3 are the same.

In some regions, code officials may not allow the use of two methods on one story.In such cases, use Method 3 for interior walls.

Your choice of method will be influenced by the customers request or localpractices. Investigate these factors before proceeding.


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Wall Bracing 401 36

specify the location of the braced wall panels, you need to know how wide each panelcanbe, so that you can fit them into the available wall space.

The next section discusses the IRC requirements for braced wall panel widths.

Width of Braced Panel

The panel width is the controlling factor for prescriptive solutions for all braced wall typeslisted in the code. The code accepted width is 4.

Figure 23: Braced Wall Diagrams

A 4-wide panel at a corner provides fullbenefit for prescriptive bracing and willresist shear forces.

[The dotted area represents a braced wall panel.]

The IRC uses a height-to-width ratio (aspect ratio) toestablish the minimum panel width to ensure thepanel can resist lateral forces.

In Figure 23, as the braced wall panel gets thinner, it

becomes less and less capable of resisting slidingand uplift forces.

Eventually, the panel cannot provide adequateresistance.

The IRC does not recognize braced wall panelwidths less than 4.

However, prefabricated, code accepted panels andsome alternate field-built panels can be used in wall

sections narrower than 4 wide.A 2-wide field-built panel provides muchless resistance to shear forces and is notcode accepted as a braced wall panel. A24" panel may be acceptable for acontinuously sheathed house.Prefabricated panelsmay provide asolution in such situations.

A 12-wide field-built panel providesvirtually no resistance to shear forces andis not code accepted.. Prefabricatedpanelsmay provide a solution in suchsituations.


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Wall Bracing 401 39

Portal Frame - Braced Wall Panel Adjacent to Door or Window Opening

The 2006 IRCs second alternative braced wall panel is a field-built portal frame(R602.10.6.2). The portal is similar to the alternate-braced wall panel, but requires acontinuous header over the two panels, or a panel and column. The portal also requirestwo hold-downs of 4200 lbs on each panel and two1000 lb straps connecting the panel to

the header.

The code allows field-built portal frames to be on one side or both sides of an opening(Figure 27).

Figure 27: Schematic of 2007 IRC Supplement -Field-built Single and Double Portal Frame

Labels and Notes on Plans

Label field-built portals on planswith a callout that begins with thewidth of the panel in inchesfollowed by FPS for a single portalorFPD for a double portal.

For Example:

16FPS = 16 Field-Built Portal,

Single

Refer to Appendix C for moreguidance on notes on plans.

Headercontinues overthe anel

Hold-downs


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Wall Bracing 401 43

Table 3 may be used when specifying continuous sheathing. In continuous sheathingapplications, all areas of the wall must be sheathed including the areas above and belowthe openings. But remember that sections of a wall that contain openings cannot act asbraced panels.

This table shows the minimum width required for a braced panel next to an opening.Notice that the required width of the braced panel is affected by the height of the largestadjacent opening. If a wall segment has a door on one side and a window on the other, usethe minimum length requirement for the door opening.

Table 3: Method 3: Continuous Sheathing - Fully Sheathed Exterior Walls

WallHeight

Minimum Width of Braced Panel to Adjacent Opening1,2,3

FullHeight

Opening100%

Door

85% of wallheight

Window

65% of wallheight

Garage Door41-Story

4:1 aspect ratioPrefabricatedShear Brace

848 32 24 24

12 minimum9 54 36 27 27

10 60 40 30 30

1) Based on 2006 IRC Section R602.10.52) Special interior and exterior corner detail required for all cases. Figure R602.10.53) Prefabricated panels or engineering can always be substituted for any width in the first story.4) Walls based on 4:1 height-to-width ratio. Table R602.10.5 footnote (b).

Another important point to remember when using this table is that any braced wallsegment located next to wall openings must meet IRC requirements for width. Its stilladvantageous to use continuous sheathing in certain cases because its possible to

consider braced wall segments that are narrower than 4-0. But keep in mind: whencalculating wall bracing, a 27 wall bracing segment equals 27, not 48in the calculation.

For Example:

Suppose a 40-0 wall line with multiple windows has three sections with widths of 32, 30,and 28.

The story is 8-0 tall. (Find in Column 1.)

Under these conditions, wall bracing segments next to the windows may be 24wide or wider. (Find in Column 4.)

In this case, all three segments are wider than 24 and may be used. Method 3 (requiredfor continuous sheathing applications) requires 16% of the wall line to be braced.

Therefore, the total of these wall segments must be at least 16% of the wall line length:

32 + 30 + 28 = 90 = 7.5

7.5I 40 = 18.75%18.75% > 16% OK


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Wall Bracing 401 45

30 30 30 30

18 18

38-0

Quick Check 3-3

Try using the tables in this section to determine the percentage and footage of braced wallpanels required for this example.

Assume the following conditions:

Wind Speed= 90 mph Seismic Design Category = A

Story Location = 1st floor of a 2-story home

IRC Method = Method 3 Continuous Sheathing

Wall height = 9-0

What is the length of the braced wall line shown above? ________

What percentage of this length must contain braced panels? (Use Table 1.) ________

How many total feet of braced wall panel do you need?(Braced Wall Line Length) x (% factor from Table 1.) = ________

Is the wall width adjacent to the windows adequate for a braced panel? (Use Table 3.)

Required width per Table 3: __________

Actual width on plans: ___________

OK? _________

Is the wall width adjacent to the door adequate for a braced panel? (Use Table 3.)

Required width perTable 3: _______

Actual width on plans: ___________

OK? _________

Is the wall space available for braced panels adequate?

(Sum of total braced wall panels) _______ > (Total required) ________?

(Answers on page 67.)

4-0


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Wall Bracing 401 - 48 -

Step 3. Determine percentages and length of bracing required(For guidance on Step 3, see page 33.)

Use Table 1: Simplified Version of IRC 2006 Table R602.10.1 on page 34. Youllneed to know the following to use this table:

Wind speed and seismic design category

Story location (first, second, or third story) IRC bracing method number

Write down bracing percentages needed for each method used.

Determine how many feet of wall must contain braced panels. Multiply thepercentage by the length of the braced wall line. (You figured the wall line lengthin step 1.)

Step 4. Determine locations of panels and check against minimum panelwidths

(For guidance on Step 4, see page 33 - 44.)

For walls without continuous sheathing (braced panel system), Method 3: Use Table 2 on page 43 to check minimum braced panel widths.

Braced panels must be every 25 on-center and no more than 12-6 fromany exterior corner.

For continuously sheathed walls, Method 3:

Use Table 3 on page 43 to check minimum-braced panel widths.

For interior-braced wall lines, Method 5:

Use Table 4 on page 44 to find equivalent braced panel widths

Add up all braced panel widths that qualify and check the actual bracingpercentage against the percentage required for each wall.

For Cripple Walls Fully sheathe all cripple walls at side-stepped foundations.

For Gable End walls (not noted in code)

Fully sheathe all gable end walls.

Include relevant notes on the plans. Refer to Appendix C.


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Prescriptive Wall Skill Check 1Braced Panel System

For the plan below, select a set of braced wall lines in the longitude and transversedirections. Calculate the exact number, width, and type of panel to be used in eachbraced wall line (using Table 2). Use the work sheet on the following pages forcalculations. Highlight and label your wall bracing solutions on the plan below. (Refer toAppendix C for guidance on how to label panels.)

Assume these conditions:

Wind Speed = 90 mph Seismic Design Category = A.

Floor Location = First story of a two-story home. 9. wall height.

Builder uses only the minimum amount of required bracing.

1

2

3

A B C E


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Prescriptive Wall Skill Check 2Continuous Sheathing

Youve done it! Youve learned how to specify braced walls in prescriptive applications.Just to verify your knowledge, try specifying bracing for the same structure usingcontinuous sheathing. Select a set of braced wall lines in the longitudinal and transversedirections. Check the available wall space for braced wall panels (Table 3). Highlight andlabel your solution on this page. Use the work sheet on the following pages forcalculations.

Assume these conditions:

Wind Speed = 90 mph wind Seismic Design Category = A.

Floor Location = First story of a two-story home (9 wall height).

Builder will fully sheathe entire home (i.e.: continuous sheathing).

1

2

3

A B C E


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Wall Bracing 401 High Seismic Supplement 56

Step 4.Determine locations of panels Do I have panels within 12-6 of the corner of the wall line?

Are the offset within the allowable limits?

Do I have adequate wall space to place the panels?

Have I considered requirements for interior wall lines and garage opening?

[Highlight panel locations on the plan]

Step 5.Determine braced panel types and alternates where necessary Do I have garage returns or other wall lengths less than 4?

Do I have cripple walls?

Do I have gable end walls?

[Refer to theProcedure for Specifying Prescriptive Solutions Per Story for guidance onthese issues. Mark changes on the plans as necessary.]


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Worksheet for Calculations

Step 1. Define the braced wall lines Braced wall line 1 (transverse) Length _____

Braced wall line 2 (transverse) Length _____



Braced wall line A (longitudinal) Length _____

Braced wall line B (longitudinal) Length _____

Braced wall line C (longitudinal) Length _____

Braced wall line D (longitudinal) Length _____

Braced wall line E (longitudinal) Length _____

Step 2. Determine the IRC Method to apply Braced wall line 1: Method _____

Braced wall line 2: Method _____



Braced wall line A: Method _____

Braced wall line B: Method _____

Braced wall line C: Method _____

Braced wall line D: Method _____

Braced wall line E: Method _____

With Method 3: Braced panel System or Continuous Sheathing? _____________

Step 3. Determine percentages and length of bracing required Table R602.10.1 Method 3 _________% Method 5 _________%

[Total Length of wall lineX percentage= minimum feet of braced wall panels]

Braced wall line 1 needs _____ ft. of braced wall panels.




Braced wall line A needs _____ ft. of braced wall panels.

Braced wall line B needs _____ ft. of braced wall panels.

Braced wall line C needs _____ ft. of braced wall panels.

Braced wall line D needs _____ ft. of braced wall panels. Braced wall line E needs _____ ft. of braced wall panels.

Worksheet for Calculations (cont.)

Step 4. Determine locations of panels and check against minimum panelwidths


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Are the offsets within the allowable limits?

Do panel widths meet minimum width criteria?

Does the total of all panel widths equal or exceed the required length needed

for each braced wall line?

For walls without continuous sheathing and for Method 5, do I have panelswithin 8-0 of the corner of the wall line and panels 25 on center?

Is the IRC requirement met for 2 of sheathing at the corners or an 1800 lbs.

hold down? (If using hold downs, be sure note it on the plans.)

[Highlight panel locations on the plan]

Step 5. Determine alternates where necessary Do I have a solution for garage returns or other wall lengths less than 4?

Do I have cripple walls?

Do I have gable end walls?

[Refer toWall Bracing 401, Procedure for Specifying Prescriptive Solutions Per Storyfor guidance on these issues. Mark changes on the plans as necessary.]


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AppendicesAppendix A Hints for Designers

1. Reminders:

Establish braced wall lines to resist wind or seismic loads. Once braced wall lines are identified, find wall space (width) to accommodate

options presented by the code. Only use iLevel

wall bracing solutions when

prefabricated solutions are necessary.

2. For two- or three-story homes, evaluate the uppermost story first. Because of the 4restriction for panel widths, prefabricated panels or full (continuous) sheathing may berequired. All code portal options require direct contact with concrete. Consider the

iLevel

Shear Brace for second story applications.

3. When calculating wall bracing percentages, use feet as the basis rather than mixingfeet and inches unless, of course, you are using a calculator that accepts feet/inchinput.

1 = 0.08 4 = .33 7 = 0.58 10 = 0.82

2 = 0.16 5 = 0.42 8 = 0.67 11 = 0.91

3 = 0.25 6 = 0.50 9 = 0.75

4. When calculating wall widths for bracing, use actual window and door sizes asspecified, and deduct 2 from each width to allow for rough opening. Alternately,actual rough openings can be used for calculations.

5. Provide details of the code alternate braced panel and portal if used in the design. Forreference, see IRC Section R602.10.6.

6. If the 25 center-to-center spacing of panels cannotbe achieved on any given braced wall line, tryshifting the end panels into the wall line (up to 12-6maximum). The old 2000 IRC rule that panels mustbe at the end of each wall is no longer valid.

7. For simplicity, call out full sheathing for cripple walls.

8. Where space is severely limited (i.e., at garagereturns of 12), consider the thickness of the wall. A12 return with a 5-thick wall equals 17 ofavailable wall width. A 16 portal frame fits into thisspace (Figure 29).

Figure 29: 12" Return


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Appendix B 50-ft Braced-line ExceptionIn buildings where walls in Seismic Design Categories A C cannot be identified thatmeet the 35 minimum distance between braced wall lines, the code allows a maximumup to 50 (IRC R602.10.1.1) as long as:

The provided wall bracing equals or exceeds the amount required by

Table R602.10.1 multiplied bya factor equal to:

[Braced wall line spacing] I 35

The length-to-width ratio of the floor/roof diaphragm does not exceed 3:1.

To apply the exception:

Select a bracing method.

Determine the wind speed and seismic category.

Use Table 1 on page 34 to find required bracing percentages for this particularstory level.

Multiply this percentage by a factor equal to the braced wall line spacing I 35.

Calculate a diaphragm width/length ratio.

For Example:

Using the plan in Skill Check 1 in the longitude direction (lateral force direction is from topto bottom of the page):

One of the interior-braced wall lines (B orD) could be eliminated.

Assume braced wall line B was re-specified to include large openings, eliminatingthis wall as a braced wall line.

The revised braced wall line dimensions are as follows:

Modified percentages of Table R602.10.1: 37/35 = 1.06

Braced wall lines A and C, using Method 3 exclusively, requires 16% x 1.06 = 17%bracing

Braced Wall line A is 29% braced > 17% O.K.

Braced Wall line E is 33% braced > 17% O.K.

Braced wall line D, using Method 5 exclusively, requires 25% x 1.06 = 27% bracing

Braced Wall line D is 31% braced > 27% O.K.

Length -to-width ratio of the diaphragm (ignore the garage):

54.5/35 = 1.56 < 3 O.K.


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Appendix C Suggestions for Typical General Notes onPlansHere are some suggestions regarding General Notes you might include on plans:

Lateral force information

Add the following data to general notes with design floor and roof vertical loads. Wind Speed _______ mph

Wind Exposure ____ (A, B, C, D; on the plans but not needed for prescriptive solutions)

Seismic Design Category _______ (A, B, C)

Braced Wall LinesBraced wall lines and panel locations are indicated on plans per the following schedule.

Detail Description

48WSP 48 Wood Structural Panel

CS Continuous sheathing on this wall, including above and below all openings. 7/16sheathing on one side of wall. Block all edges and nail with (2) 3/8 x 0.113 nails (m) at6 centers at all edges and 12 centers in the field.

24CSP Continuous Sheathing Panel. 24 width of 7/16 sheathing one side of wall. Block alledges. Nail with 2-3/8 by 0.113 nails at 6 centers at all edges and 12 centers in thefield.

32ABP 32 alternate-braced panel; construct per IRC 2003 R602.10.6

16FPS

16FPD

16 field-built portal, single (one panel on one side of opening)

16 field-built portal, double (one panel on each side of opening)

Construct per 2004 IRC Supplement R602.6.2

*for single story buildings only

24FPS

24FPD

24 field-built portal frame, single (one panel on one side of opening)

24 field-built portal frame, double (one panel on each side of opening)

Construct per 2004 IRC Supplement R602.6.2

**for 2-story buildings12MP

12MPS

12MPD

12 prefabricated panel

12 prefabricated portal, single (one side)

12 prefabricated portal, double (one on each side of opening)

Exact size and construction per manufacturers recommendations

48G2 48 length of gypsum one side of wall. gypsum, block all edges, nail with1-5/8 x 0.086 nails or 6d common (2 x .131) nails at 7 o.c.

96G1 96 length of gypsum one side of wall. gypsum, block all edges, nail with1-5/8 x 0.086 nails or 6d common (2 x .131) nails at 7 o.c.

1) Braced panel minimum widths are shown on plan details. Contractor may increase width of any panel, but cannotdecrease panel width.

2) Braced panels are full height and extend from sill or bottom plate to top of double-top plates. Where not

dimensioned, use 25 maximum spacing (center to center) between panels.3) Provide single joist or blocking under all interior-braced wall lines and nail bottom plate of designated-braced wall

panels with 3-16d nails at 16 o.c.

Details

If used, add details for alternate braced panel, exterior corner details, and field-built portal frames.


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Appendix D IRC Comparison MatrixUse this matrix to identify variations in wall bracing criteria from one version of the IRC toanother.

IRC Section 2006 IRC 2000 IRC 2003 IRC2007 Supplementto the 2006 IRC

R602.10.1Braced WallLines

Corner offset of 12-6 maxWall line offset of 4 max, 8 total

Same as2006 IRC

Same as2006 IRC

R602.10.1.3R602.10.1 addsvariations toallowable bracingStory to storyvariationWall line to wall linevariation except incontinuoussheathingSDC A and B maymix methods withina wall line whenusing higherbracing percentage

(except continuoussheathing)

R602.10.1.1Braced WallLine Spacing

Maximum 35 o.c.

Exception: 50 o.c. OK when wallbracing is increased by a ratio of thelength of the braced wall line dividedby 35 and the length to width ratio ofthe floor or roof diaphragm are lessthan 3:1

No LimitSame as2006 IRC

R602.10.1.4

R 602.10.3Braced WallPanelConstruction

8 methods as listed inWall Bracing 401 trainingGives material, required nailing andstud spacing

Same as2006 IRC

Same as2006 IRC

R602.10.2Method 3: 3/8 thickwood structuralpanel for 16 and24 o.c. studs

R602.10.4Length ofBraced Panel

4 for Methods 2,3,4,6,7,8 and Method5 when double sided8 for Method 5, single sided

Same as2006 IRC

Same as2006 IRC

R602.10.3For method 5 singlesided applications,percent bracingmust be doubled

R602.10.5ContinuousSheathing

All exterior and interior walls must befully sheathed with wood structuralpanels including areas above andbelow openingsPanels with a 4:1 aspect ratio may beused around the garage

A portal with a 6:1 aspect ratio may beused with 2 anchors on either side ofportal

No portaloption

No portaloption

R602.10.4 -Continuouslysheathed panel andportal optionsaround garage nowin text. SectionsR602.10.4.5 andR602.10.4.6R602.10.4.7Requirescontinuoussheathing on entirestory in SDC D0-D2and areas withwinds above 100mph


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R602.10.6.1AlternateBraced Wall

Panel

32 wood structural panel2 anchor bolts2 hold downs of 1800 lbsRequires foundation or floor abovecontinuous footing

Two story house must use sheathingon both sides of panel and 2 holddowns of 3000 lbs

Same as2006 IRC

Same as2006 IRC

R602.10.3.2.1Two story housesheathed on oneside only with nailsat minimum 4 o.c.

along edge

R602.10.6.216 and 24Portal Options

16 portal using wood structuralpanels and 10 maximum heightSheathing extends over header6-18 header span1 anchor bolt2 hold downs of 4200 lbs eachFor two story house need 24 portal

No portaloption

No portaloption

R602.10.3.2.2

R602.10.7Panel joints

All vertical panel joints over studsAll horizontal joints over blocking

Same as2006 IRC

Same as2006 IRC

Same as 2006 IRC

R602.10.8Connections

Blocking required when a braced wallline is above perpendicular joists

When joists are parallel to a bracedwall line, rim joist or other parallelframing member must be provided

No rimjoist

requiredfor

support

No rimjoist

requiredfor

support

R602.10.5 and

R602.10.6

R602.10.9ContinuousFoundationBeneathInterior BracedWall Lines forSDC D2

One story buildings in SDC D2, interiorbraced wall lines supported oncontinuous foundation not exceeding50. Two story buildings have allinterior braced wall panels supportedon continuous foundations.

Exception: for two story structures,continuous foundations under interiorbraced wall lines at 50 if cripple wallheight less than 4, first floor bracedwall panels supported by doubledfloor joists, continuous blocking, orfloor beams, and distance betweenbraced lines doesnt exceed twice thebuilding width.

Same as2006 IRC

Same as2006 IRC

R602.10.6.1

R602.10.10Design ofStructuralElements

If a portion of a building does notcomply with bracing requirements,that portion is designed andconstructed with acceptedengineering practice.

Same as2006 IRC

Same as2006 IRC

No guidance in wallbracing section

R602.10.11High SeismicBraced WallLines

Structures in SDC D0 D2 haveexterior and interior braced wall lines.

No D0Category

No D0Category

R602.10.1.4.1

R602.10.11.1Braced WallLine Spacing

Maximum 25 o.c.

Exception: Spacing less than 35 o.c.for one room of maximum 900 ft

2.

Spacing between all other lines max25 o.c. (1-2 story house)

Same as2006 IRC

Same as2006 IRC

R602.10.1.4.1Length to widthratio of diaphragmless than 3:1


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R602.10.11.2Braced WallPanel Location

Exterior wall lines have panel at eachend

Exceptions: Braced panel may beoffset 8 from wall end if a 24 wide

panel is applied to each side of thecorner and the panels are attached tothe framing as shown in Figure602.10.5.

ORSide of the braced wall panel closestto the corner has tie down fastened tothe stud and having an uplift capacityof 1800 lbs.

Max 12from

cornerSame as2006 IRC

R602.10.1.3.1 andR602.10.4.3Tie down of 800

lbs

R602.10.11.3Collectors

Designed collector required for morethan 8 from end

R602.10.11

R602.10.11

No guidanceoffered

R602.10.11.5No adhesive attachment in highseismic regions

R602.10.11

R602.10.11.2

R602.10.2.2


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Answers to and Quick Checks and Skill ChecksSection 1 Quick Check

1. A Lateral Force is most often caused by: Wind or earthquake

2. The three effects of lateral forces that a building must resist are:

Overturning and sliding

3. Lateral load perpendicular to the wall studs is transferred to the diaphragm,which transfers this load into the walls parallel to the wind or seismic load.

Section 3 Quick Check 3-1

Braced Wall Line #1 (top) = 54-6

Braced Wall Line #2 (middle) = 54-6

Braced Wall Line #3 (bottom) = 21-3


1. According to IRC Table R602.10.1., what percentage of the wall must contain bracedpanels?

Since this is an exterior wall, it makes more sense to applyMethod 3, therefore Minimum bracing is16%.

2. How many feet of this wall must contain braced panels?

40 x 0.16 =6.40 (total width of structural panels).

3. Is it possible to use code accepted 4 panels to meet IRCbracing requirement?

Yes. All requirements can be met by placing 2 panels:

One 4 braced panel at the lower end

One 4 braced panel in middle section 12.5' from wall end.

4 + 4 = 8 > 6.40OK

12-6


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1. What is the length of the braced wall line shown above? 38

2. What percentage of this length must contain braced panels? 16%

3. How many total feet of braced wall panel do you need?

(38) x (0.16) =6.1

4. Is the wall width adjacent to the windows adequate for a braced panel?

Required (27) < Actual (30) OK

5. Is the wall width adjacent to the door adequate for a braced panel?

Required (36) > Actual (18) NOT OK

6. Is the wall space you have for braced panels adequate?

Place 1 30 braced panel at each location adjacent to the windows

(30 x 4 panels = 120 =)10 > 6.1 OK

Section 3 Quick Check 3-41. Shear walls are designed; braced walls are prescriptive. True

2. A structure should include braced wall lines in the longitudinal as well as thetransverse directions.

3. Braced wall lines include a braced wall panel every 25 along the wall line.

4. For prescriptive applications, maximum offset distance permitted in a braced wall lineis 4 per offset, 8 total offset.

5. Braced wall lines should be spaced no more than 35 apart.

6. The minimum shear brace width for continuous sheathing per code is varies based

on height of the wall, story designation, and adjacent openings.


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Answer to Skill Check 1

Longitudinal Braced Wall Lines

B D

C

E

A CB D E


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Answers - Worksheet for Calculations Skill Check 1

Step 1. Define the braced wall lines Braced wall line 1 = 21.25

Braced wall line 2 = 54.5


Braced wall line A = 55.16

Braced wall line B = 31 (or 55.16)

Braced wall line C = 24.2 (or 55.16)

Braced wall line D = 39

Braced wall line E = 35

Step 2. Determine the IRC Method to apply Braced wall line 1 use Method 3

Braced wall line 2 use Method 5


Braced wall line A use Method 3

Braced wall line B use Method 5

Braced wall line C use Method 3

Braced wall line D use Method 5

Braced wall line E use Method 3

Can I use Method 3 for walls with a braced panel system rather than continuous

sheathing? yes

Step 3. Determine percentages and length of bracing required Table R602.10.1 Method 3 __16% Method 5 ___25%


Braced wall line 1 needs _3.36_ ft. of braced wall panels.



Braced wall line A needs _8.8_ ft. of braced wall panels.

Braced wall line B needs _7.75 (or 13.8)_ ft. of braced wall panels.

Braced wall line C needs _3.8 (or 13.8) ft. of braced wall panels.

Braced wall line D needs _9.75_ ft. of braced wall panels.

Braced wall line E needs _5.6_ ft. of braced wall panels.


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- 73 -

Answers to Skill Check 2

Longitudinal Braced Wall Lines

48

48

48


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- 75 -

Answers - Worksheet for Calculations Skill Check 2

Step 1. Define the braced wall lines Braced wall line 1 = 21.25



Braced wall line A = 55.2

Braced wall line B = 31 (or

55.2)

Braced wall line C = 24.2 (or

55.2)

Braced wall line D = 39

Braced wall line E = 35

Step 2. Determine the IRC Method to apply Braced wall line 1 use Method 3



Braced wall line A use Method 3

Braced wall line B use Method 5

Braced wall line C use Method 3

Braced wall line D use Method 5

Braced wall line E use Method 3

Can I use Method 3 for walls with a braced panel system rather than continuous

sheathing? no

Step 3. Determine percentages and length of bracing required Table R602.10.1 Method 3 __16% Method 5 ___25%






Braced wall line B needs _7.75_ ft. of braced wall panels.

Braced wall line C needs _3.84_ ft. of braced wall panels.


Braced wall line E needs _5.6_ ft. of braced wall panels.


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Step 4. Determine locations of panels, braced panel types

Braced wall line 1

18.25 braced; 18.25/21 = 87% > 16% OK

Braced wall line 2

Left to right:

Approximately 16 sheathing inside garage wall.

Right side of garage/house door: wall length is 2.66 < 36 min. (Table 3).

This section of wall, although sheathed, will not count toward the bracingpercentage because it is narrower than 36 (adjacent to a door).

Front entry: About 12 of wall space exists on each side of the entry door. Thesesections, although fully sheathed, will not count toward the required bracingpercentage.

Front bump-out: 12 prefabricated shear brace on each side of the two 4050windows.

Using the table on page 21, 27 is the minimum required width for a braced

panel. The 24 space on each side is insufficient for placing braced panels.However, a 16 or 12 prefabricated shear brace is acceptable to support asecond floor. Use 16 or 12.

Right side of home: 4.75 + 4.5 of sheathing on each side of window.

Total bracing this wall: 16 + 2 x (2 x 1.5) + 4.75 + 4.5 = 31.25/54.5 = 57% > 16% OK

Braced wall line 3 (transverse) length = 54.5

Continuous sheathing did not significantly change the requirements for portalframes, alternate-braced panels, or prefabricated panels. The minimum widths ofwall needed to provide bracing drive the need for special bracing.

Left to right:

4 OK

8.66 OK

5.25 OK

5 OK

3.25 adjacent to window > 27 OK

Total bracing: 3.25 + 4 + 8.66 + 5.25 + 5 + 3.25 = 29.41/54.5 = 54% > 16% OK


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Answers to Skill Check 3

Longitudinal and Transverse Braced Wall Lines

7-8

3

6080

6

2

6

14

3214 12

5-67

(2) 4050

12

(2) 4050

10 4-6

3050

52

4

18

12MP t .

12MP

12MP

20

48

3-6

4

6

12

6040

123

8

44

422

6-3

12MP

10

12MPD

32ABP or12MPD t .

(4)2040

(2)3050

2

3050

4

4

5040

4

16 Overhead Garage Door

BWLA

BWLB

BWLC

BWLD

BWL

BWL 1

BWL 2

BWL 3

BWL 4


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Answers to Skill Check 3 (cont.)

Step 1. Define the braced wall lines Braced wall line 1 (transverse) Length _ 44 ft

Braced wall line 2 (transverse) Length _ 44 ft



Braced wall line A (longitudinal) Length _52 ft

Braced wall line B (longitudinal) Length _32 ft (not required if 35 o.c. exception is used)

Braced wall line C (longitudinal) Length _20 ft

Braced wall line D (longitudinal) Length _48 ft

Braced wall line E (longitudinal) Length _40 ft

Step 2. Determine the IRC Method to apply Braced wall line 1: Method __3__

Braced wall line 2: Method __3/5_

Braced wall line 3: Method __3/5_

Braced wall line 4: Method __3__

Braced wall line A: Method __3__

Braced wall line B: Method __5__

Braced wall line C: Method __3/5_

Braced wall line D: Method __3/5_

Braced wall line E: Method __3__

Step 3. Determine percentages and length of bracing required

Table R602.10.1 Method 3 __45 ___% Method 5 ___60___%[Total Length of wall lineX percentage= minimum feet of braced wall panels]






Braced wall line B needs _19.2_ ft. of braced wall panels.

Braced wall line C needs _12 _ ft. of braced wall panels.


Braced wall line E needs _18 _ ft. of braced wall panels.

Answers to Skill Check 3 (cont.)


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Step 4. Determine locations of panels and check against minimum panelwidths (Includes Step 5)

Braced wall line 1

Need 5 braced wall panels

Use 1 12 prefabricated double portal (12MPD)

1 4 ft wood structural panel (48WSP)

2 32 alternate braced panels (32 ABP) or 12 prefabricated panels (12MP)

Total bracing = 2 * 4 equivalent panels + 1 * 4 panel + 2 * 4 equivalent panels = 20

20 > 19.8 OK

Braced wall line 2


Use 5 4ft double sided gypsum braced panels (48G2)

1 4 ft wood structural panel

1 12 prefabricated panel

Total bracing = 5 * 4 panels + 1 * 4 panel + 1 * 4 equivalent panel = 28

28 > 26.4 OK

Braced wall line 3


Use 5 4ft double sided gypsum braced panels

1 4 ft wood structural panel

1 12 prefabricated panel (or 32 alternate panel if space is available)

Total bracing = 5 * 4 panels + 1 * 4 panel + 1 * 4 equivalent panel = 2828 > 26.4 OK

Braced wall line 4


Use 1 12 prefabricated panel on left side of wall line

1 4 wood structural panels on right side of wall line

1 7-6 wood structural panels on right side of wall line

Total bracing = 1 * 4 equivalent panel + 1 * 4 panel + 1 * 7.5 panel = 15.5

15.5 > 14.4 OK


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I Level Wall Bracing

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