Presented by the Wood Truss Council of America

Presented by the Wood Truss Council of America
Educating Professionals on the Future of Framing Storage, Handling, Installing and Bracing of Metal Plate Connected Wood Trusses Welcome to the Wood Truss Council of America’s Truss Technology Workshop. This presentation discusses industry recommendations for storage, handling, installing and bracing of metal plate connected wood trusses. ™ Presented by the Wood Truss Council of America

Outline 1.0 Responsibilities 2.0 Guideline Documents
3.0 Job Site Storage 4.0 Handling 5.0 Installation 6.0 Fall Protection 7.0 Temporary Bracing 8.0 Permanent Bracing 9.0 Construction Loading 10.0 Handling, Installing, & Bracing Video The presentation consists of ten sections on storage, handling, installing and bracing information in addition to design responsibilities, fall protection, construction loading and will culminate in a short video presentation on bracing.

1.0 Responsibilities 1.0 Responsibilities 2.0 Guideline Documents
3.0 Job Site Storage 4.0 Handling 5.0 Installation 6.0 Fall Protection 7.0 Temporary Bracing 8.0 Permanent Bracing 9.0 Construction Loading The first section on Responsibilities discusses who in the construction process is responsible for the different aspects of storage, handling, and bracing of metal plate connected wood trusses.

1.1 Standard Responsibilities
ANSI/TPI Referenced in: IBC & IRC Developed by the Truss Plate Institute The International Building Code and the International Residential Code both state that trusses should be designed and manufactured according to ANSI/TPI [Antsy-TPI-One-Two Thousand Two] The National Design Standard for Metal Plate Connected Wood Truss Construction from the Truss Plate Institute.

1.1 Standard Responsibilities
Owner Building Designer Contractor Truss Manufacturer Truss Designer Chapter 2 of ANSI/TPI 1 contains the industry recommended guidelines for Standard Responsibilities in the Design Process Involving Metal Plate Connected Wood Trusses. This document discusses the five parties involved in the design and manufacture of wood trusses – owner, building designer, contractor, truss manufacturer and truss designer. It also discusses, among other things, who is responsible for designing, supplying and installing the bracing of wood truss systems.

1.2 Contractor Responsibilities
Receiving Unloading Storage Handling Installation Temporary Bracing The builder, building contractor, licensed contractor or installation contractor is responsible for the proper receiving, unloading, storage, handling, installation, and temporary bracing of metal plate connected wood trusses. Prior to truss erection, the builder/contractor should meet with the erection crew for a safety and planning meeting, making sure each crew member understands his or her roles and responsibilities during the erection process.

1.3 Bracing Responsibilities
Truss Designer: Location of permanent truss member bracing Building Designer: Permanent bracing design for the entire structure including the truss system The Truss Designer is responsible for preparing the Truss Design Drawings and for specifying the locations of any required permanent truss member bracing. The Building Designer is responsible for preparing the Construction Design Documents and the permanent bracing design for the entire structure including the truss system. For more information on Standard Responsibilities, see the Truss Technology Workshop on that topic.

Quiz 1

2.0 Guideline Documents 1.0 Responsibilities 2.0 Guideline Documents
3.0 Job Site Storage 4.0 Handling 5.0 Installation 6.0 Fall Protection 7.0 Temporary Bracing 8.0 Permanent Bracing 9.0 Construction Loading Section 2 covers industry guidelines that aid in the handling, installing, and bracing of metal plate connected wood trusses.

2.1 Bracing Guidelines Building Component Safety Information
BCSI 1-03 Booklet Guide to Good Practice for Handling, Installing & Bracing Metal Plate Connected Wood Trusses The truss industry provides bracing guidelines in the Building Component Safety Information BCSI 1-03 [One-Oh-Three] booklet. This booklet is the Guide to Good Practice for Handling, Installing & Bracing Metal Plate Connected Wood Trusses. The eleven sections of the booklet are summarized in the BCSI series - B1 through B11. They are printed so that they can be easily included in the truss manufacturer's jobsite packages.

2.2 Jobsite Packages Truss Documentation BCSI Guides
The jobsite package contains specific project information like the truss placement diagram or “layout” and the truss design drawings which are information sheets on each of the particular truss designs for the project. These contain important notes on permanent bracing, hangers, and how to fasten girder plies together. The package also contains guides for handling, installing and bracing. This example shows the pre-assembled WTCA/TPI jobsite package which contains summary sheets B1 through B4.

2.3 Jobsite Delivery Once the Truss Manufacturer delivers the truss order to the job site, they turn over the trusses and the jobsite information package to the buyer. The truss manufacturer has no ability to enforce these recommendations. Framers must be knowledgeable enough to follow good practices so that the trusses will be installed properly as a permanent part of the structure with no damage to life or property as the installation process takes place.

2.4 B1 Summary Sheet WTCA-B1 Warning Poster HIB-91 Sheet
The B1 Summary Sheet presents the BCSI-B1 section in a 11 by 17 inch poster format. It is a full-color document that summarizes the main points of B1. It is blank on one side for printing Truss Placement Diagrams or construction plans. It is available in several different sizes for printers and plotters. The B1 Summary Sheet replaces the HIB-91 Summary Sheet and the WTCA B1 Warning Poster. HIB-91 Sheet

2.5 B2 Truss Installation & Temporary Bracing
The second document in the B-series is B2. It focuses on Truss Installation & Temporary Bracing.

2.6 B3 Web Member Permanent Bracing/Web Reinforcement
The B3 document on Web Member Permanent Bracing and Web Reinforcement.

2.7 B4 Construction Loading
B4 Construction Loading replaces the Truss Technology in Building Brochure by the same name.

2.8 Bracing Warning Tags Some truss manufacturers may also attach warning tags to individual trusses. These tags and refers installers to the BCSI and jobsite package materials for information on how to perform proper installation of temporary bracing of trusses.

2.9 BCSI Series The remainder of the BCSI series may be included in the truss manufacturer’s jobsite depending on the project specifics. The titles are as follows: B5 Truss Damage, Jobsite Modifications and Installation Errors B6 on Gable End Frame Bracing B7 on Temporary and Permanent Bracing for Parallel Chord Trusses B8 Toe-Nailing for Uplift Reactions….

2.9 BCSI Series B9 Multi-Ply Girders
B10 Post Frame Truss Installation and Bracing and B11 Fall Protection and Wood Trusses

Quiz 2

3.0 Job Site Storage 1.0 Responsibilities 2.0 Guideline Documents
4.0 Handling 5.0 Installation 6.0 Fall Protection 7.0 Temporary Bracing 8.0 Permanent Bracing 9.0 Construction Loading The following section covers the proper way to store trusses at the job site.

3.1 Long Term Storage Where possible use blocking to keep trusses off the ground. This is particularly important for long term storage. To avoid distorting the plane of the trusses and collecting moisture from the ground, trusses should be stored flat, on level grade, and on blocks. As shown, blocking should be used on eight to ten foot centers.

3.1 Long Term Storage Trusses should not be left exposed or in contact with the ground for more than one week. Otherwise, place them on blocks or cover them to reduce moisture gain. It is important for the lumber that it be kept as dry as possible. Short term moisture content gains are not usually a problem. Long term exposure can be – lumber discolors and will eventually decay, and plates can loosen under repeated wetting and drying cycles.

3.2 Unsafe Storage Conditions
This a dangerous job site storage conditions and is NOT recommended. This bundle will have to be stabilized before the bands can be broken. Uneven storage conditions can cause trusses to break or warp.

3.3 Damaging Storage Condition
This condition illustrates how trusses can scatter out like a deck of cards when the bands are broken. Care should be exercised when removing banding to avoid damaging trusses. Ideally, these trusses would be braced in a stable, upright position.

Quiz 3

4.0 Handling 1.0 Responsibilities 2.0 Guideline Documents
3.0 Job Site Storage 4.0 Handling 5.0 Installation 6.0 Fall Protection 7.0 Temporary Bracing 8.0 Permanent Bracing 9.0 Construction Loading The following section covers the proper way to handle metal plate connected wood trusses.

4.1 Handle with Care The handling of metal plate connected wood trusses should be accomplished with care and expertise, and with the aid of proper equipment. Beginning with the unloading process, and throughout all phases of construction, care must be taken to avoid lateral (out-of-plane) bending of trusses. The installer should assure that trusses are properly protected against damage during handling and installation and that they are maintained in alignment before, during and after installation.

4.2 Avoid Lateral Bending The trusses are bending out of plane, which puts the top-side in severe tension and the bottom-side in severe compression. This means that some of the plates are tearing and others are buckling. The lumber is also sustaining hairline cracks that will affect the long term performance of the truss. The truss should not deflect more than a few inches during the handling procedures. The deflection shown here is probably closer to 10 feet. The contractor has bought and paid for a set of quality engineered trusses. If he does not handle and install them properly and adhere to all the notes on the engineering, he has potentially reduced the value of the product and increased the risk of poor performance.

4.3 Safe Handling with Forklift
Here four-by-two floor trusses are being lifted into place for ease of installation. This is an extremely safe approach to handling trusses. All trusses should be picked up at the top chords in a vertical position only.

4.4 Truss Handling Warning
Wear gloves and safety glasses Trusses are banded together with metal strapping. The straps are under tension and can spring back and cause injuries if they are not carefully removed. Workers should cut banding with shears, not with claw hammer which can damage the lumber. It is normal for some truss plates to extend outside the wood area of the joint. These overhanging portions of the plate are sharp. Knowledge of plate locations and safe handling techniques are important to observe to reduce the risk of injury.

Quiz 4

5.0 Installation 1.0 Responsibilities 2.0 Guideline Documents
3.0 Job Site Storage 4.0 Handling 5.0 Installation 6.0 Fall Protection 7.0 Temporary Bracing 8.0 Permanent Bracing 9.0 Construction Loading The following section covers the proper way to install metal plate connected wood trusses.

5.1 Proper Equipment All trusses that are erected one at a time shall be held safely in position by the installation equipment until such a time as all necessary bracing has been installed and the ends of the trusses are securely fastened to the building. The proper equipment should be used for lifting trusses. A crane with a spreader bar is strongly recommended for trusses with spans greater than 30 feet. A bridle with chokers may be used for trusses with spans 30 feet or less.

5.2 Lifting by Hand If the trusses are under thirty feet in length, it may be possible to lift them by hand. Use one lift support for trusses up to twnety feet and two lift supports for trusses up to thirty feet. Trusses greater than thirty feet shoul dnot be lifted

5.3 Lifting by Crane Do not lift trusses over 30 ft by peak
If trusses over thirty feet in length are being hoisted into place, do not lift them by a single pick point at the peak. The plated joint was not designed to withstand the high forces created when it is lifted like this.

5.4 Lifting Short Spans < 30’
For truss spans up to 30 feet, slings should be attached to at least two top chord joints and spaced about ½ the truss length from each other. All trusses, regardless of span, should have a tagline crews on the ground can help guide the truss as it is being lifted. Lifting the truss without a tagline to the ground is a risky practice.

5.4 Short Spans < 30’ This is an example of a good installation practice for a short span truss under twenty feet in length. The truss is being held in place with a forklift until the crews attach it to the temporary bracing in the building.

5.4 Short Span Bad Practices: Single pick point No tag line
Take a moment to look at how this short span truss is being installed. It illustrates a couple of bad practices. First, the truss is being picked up at a single point in the middle of a panel. The 2x4 at the middle of this panel certainly was not designed to support the entire weight of the truss. It is also difficult to find the balancing point for a single pick-up point on an asymmetrical truss like this. Second, there is no tag line to the ground. The truss is free to rotate. A gust of wind could rotate the truss out of control which is further compounded by the fact that it is asymmetrical and precariously balanced with one attachment point. This creates a dangerous situation for anyone working in the vicinity.

5.5 Lifting Medium Spans 30’ - 60’
For truss spans up to 60 feet, use spreader bars that are approximately one-half to two-thirds the truss length. Use at least two pick up points, located at plated joints. The outermost pick lines should angle inward or “toe-in”. This stabilizes the truss by putting the top chord in tension instead of compression which is more prone to buckling.

5.5 Medium Span 30’ to 60’ Not 1/2 Truss Length
Here is a truss being picked up from two joint locations, however, the two points are too close together and the truss is deflecting laterally. Recall that for truss spans less than 60 feet, the slings should be spaced at least one-half the truss length apart. At best, this is a third of the truss length. This results in the truss bending laterally, which should be avoided. The installers should have used a spreader bar in this case.

5.5 Medium Span 30’ - 60’ This truss is close to sixty feet in length. The installers are using a spreader bar and the attachments are toed in as recommended. There is no apparent lateral deflection but given the length of the truss, a longer spreader bar should have been considered.

5.5 Medium Span 30’ - 60’ This scissor truss is much greater than 30 feet and should not be picked up at a single point as this photo shows. There are a couple of reasons for avoiding single lift points. One is that a single hook attached to the top chord of a truss can slacken and fall off after the truss has been lowered into place. Once that happens, the truss may tip over if it is unsupported. This can be avoided by using a closed loop attachment as shown. The second point is if the hook is attached to a web member rather than the top chord. It causes the truss skew out of plane and the web can be pulled out of the joint, damaging the truss and potentially causing the truss to fall away from the attachment.

5.5 Medium Span 30’ - 60’ This attic frame is being lifted by a spreader bar with toed-in slings. The attachment points are over half the truss length apart. There is no evidence of lateral deflection, and there is a tag line on the left heel to the ground. This is a good installation.

5.6 Lifting Long Spans  60’ Finally, for truss spans greater than 60 feet, a strongback/spreader bar should be used and placed at approximately 2/3 to ¾ truss length. A long span truss can pose a greater risk to installers because the dimensions and weight of the truss itself can create instability, buckling and collapse of the truss if it is not handled, installed and braced properly. Spreader bars, adequately designed and properly used, distribute the load over members and prevent breakage. Attach it to the truss at ten foot intervals. Long span trusses can be installed safely and efficiently but they require more detailed safety and handling measures than short span trusses. See the Truss Technology In Building brochure called “Long Span Truss Installation” for more information on long span installations.

5.6 Long Span  60’ This spreader bar is too short and the attachments are toeing out, which can create compression buckling. To counteract the compression, a stiffback is attached to the center face of the truss before it is lifted.

5.6 Long Span  60’ This crew is using a nice long spreader bar that is well over half the truss length. There are four pick-up points and the truss appears to be well supported and stable even though the lines are not necessarily toeing in.

5.6 Long Span  60’ This is a perfect example of a BCSI recommended installation. The spreader bar is well over half the truss length and there are three or more pick up points.

5.7 Alignment Tolerances Trusses need to be held in a vertical position and a flat plane throughout the installation process and for the life of the structure. BCSI provides installation tolerances for these two conditions. The maximum out-of-plumb tolerance is 2 inches in the horizontal direction for trusses 8 feet deep and greater. The maximum out-of plane tolerance is 2 inches for truss spans 33 feet and greater. An experienced contractor is expected to be able to position trusses in a true and plumb position. Adequate temporary bracing will keep the trusses aligned until the permanent sheathing and bracing are installed.

5.0 Quiz

6.0 Fall Protection 1.0 Responsibilities 2.0 Guideline Documents
3.0 Job Site Storage 4.0 Handling 5.0 Installation 6.0 Fall Protection 7.0 Temporary Bracing 8.0 Permanent Bracing 9.0 Construction Loading The following section covers the topic of fall protection while installing metal plate connected wood trusses.

6.1 Fall Protection Summary Sheet
The BCSI-B11 summary sheet explains graphically how trusses are not designed to be fall protection anchors. It presents several tips for framing crews to safely and efficiently install trusses while meeting OSHA’s Fall Protection Guidelines.

6.2 The Need For Fall Protection
In general, OSHA's fall protection standard requires that anyone working at heights of 6 feet or more be provided with fall protection The workers on this job site are engaging in several unsafe practices, aside from the obvious lack of fall protection equipment. Workers should not stand on unbraced trusses, and certainly not so their weight is creating a lateral load on the truss. A two-by-six set up as balance beam is not an acceptable means of scaffolding!

6.3 B11 Fall Protection Warning
B11 does not offer specific methods for fall protection, but it does make it clear that workers must not tie off to trusses for fall protection. The use of a single truss as an anchorage point for any type of personal fall arrest system is dangerous. Fall protection and safety measures are job site and building specific. The appropriate fall protection method for a given job must be determined by a person who is qualified to design, install, and use fall protection systems and authorized to have any problems corrected. Trusses alone are not designed to support fall protection anchors

6.4 Dangerous Impact Loads
A single truss is NOT designed to withstand loads from a falling person. The impact load from a fall could cause insufficiently braced trusses to topple over on falling workers, increasing risk and injury. A single truss, if used as an anchorage point, can pull all the trusses on top of a falling person

6.5 Safer Options Option 1: Scaffolding
The BCSI-B11 offers some suggestions for fall protection methods that are safer than tying off to single trusses. One option is scaffolding. Use an approved scaffolding system that follows OSHA guidelines.

6.5 Safer Options Option 2: Roof Peak Anchor
Another option is to use an approved roof anchor installed on a completely sheathed roof system. Roof anchors are attached to the truss and used once the truss system is fully braced and sheathed. They are left in place for the life of the structure for any future maintenance work.

6.5 Safer Options Option 3: Ground Assembly
Option 3 is to pre-assemble the roof system on the ground; sheath and brace it for stability; and then lift and set it into place. This pre-assembled section can then be used as a tie-off point as necessary.

6.6 Pre-Assembled Units Pre-assembling groups of trusses on the ground prior to lifting is a good way to avoid most fall protection measures altogether. It has the added benefit of providing a stable, braced base unit from which to install subsequent trusses. This method is discussed in more detail in the Long Span TTB.

6.0 Quiz

7.0 Temporary Bracing 1.0 Responsibilities 2.0 Guideline Documents
3.0 Job Site Storage 4.0 Handling 5.0 Installation 6.0 Fall Protection 7.0 Temporary Bracing 8.0 Permanent Bracing 9.0 Construction Loading The following section covers the topic of bracing metal plate connected trusses temporarily until permanent bracing is in place. The slides in this section are shown for educational purposes only and do not necessarily reflect typical truss installations. However, most job site truss collapses occur due to lack of properly installed temporary bracing. Failure to follow industry recommendations may result in injuries to workers and damage to property.

7.1 Purpose of Bracing Support truss at right angles so it will stay in its design position The purpose of all bracing is to apply sufficient support at right angles to the plane of the truss so as to hold every truss member in its design position. When trusses are installed on a structure, they are positioned and fastened on the bearing walls and then temporary bracing is applied. The fastening and temporary bracing must hold trusses in position until permanent roof sheathing is installed. Trusses are not marked in any way to identify the frequency, or location of temporary erection bracing. Temporary bracing is left to the discretion of the erection contractor. This long span piggyback scissor truss installation is an example of correct temporary bracing.

7.2 Guideline Documents As mentioned previously in this program, the truss industry provides temporary bracing guidance for installers is provided the Building Component Safety Information booklet, otherwise known as BCSI These are joint publications of WTCA and the Truss Plate Institute.

7.3 Bracing Materials Box Nails
All temporary bracing should be a minimum size of two-by-four stress graded lumber unless specified otherwise by the building designer. Stress graded lumber includes all visually graded and machine graded lumber with strength properties as listed in the supplement to the National Design Specification for Wood Construction. Attachments between the bracing and truss should be made with 2-10 penny, 2-12 penny or 2-16 penny “box nails”. Duplex or double headed nails are a good choice to attach temporary bracing to the top chord of the truss. The lower head draws the bracing down tight to the truss while the upper head is left to pull the nail out. This photo shows a 16 penny nail versus an 8 penny duplex nail. The 16d nail will have a much higher capacity due to its larger diameter and increased length. The only other alternative is to drive the nail in all the way in order to get full load capacity. Some framers have the tendency to use a nail with one head and leave it standing so they can get the hammer claw under it and pull it out when they are ready to sheet the roof. This is not recommended because it does not adequately connect the bracing to the top chord.

7.3 Brace to Ground It is important for the builder or erection contractor to provide substantial bracing for the first truss erected. The rest of the trusses making up the system rely upon the first truss for stability. This demonstration assembly shows the different kinds of temporary bracing. The ground bracing is shown in dark blue. Notice it uses the principle of triangulation to increase stability. Also notice the lateral bracing on the top chords lines up with the vertical ground braces. This helps transfer loads efficiently out of the braced system to the ground below.

7.3 Ground Bracing Methods
The BCSI B1 and B2 summary sheets discuss recommended ground bracing methods. The first step is to determine the on center spacing of top chord laterals based on the overall truss span. Add an additional line of lateral bracing at each change in pitch. Add a line of lateral bracing at the heel if it is 10 inches or greater in height Once you have the expected locations of all the lines of top chord lateral bracing place a ground vertical at each location.

7.3 Ground Bracing Methods
B2 offers eight steps for truss installation and temporary bracing. The first few steps address the fact that there are different site conditions and ways to begin the installation process. Step 1 describes the three options for establishing a ground bracing procedure: The first option describes the ground bracing procedure just as we saw it in B1. The second option describes bracing for a multi-story structure, where “ground bracing” terminates at the framed floor below. The third option describes another interior bracing option for sites where site conditions make ground bracing impractical. The third option is a good choice for hip style roofs where the framing changes direction usually about eight feet from the end wall.

7.3 Not Ground Bracing In this photo, the first truss installed is ineffectively braced. Inadequate size of bracing material or inadequate fastening is a major cause of erection dominoing where the instability of one truss tips over the adjacent trusses one by one.

7.3 Not Ground Bracing This photo clearly shows inadequate ground bracing; it is virtually ineffective. There is a big difference between this and what BCSI recommends for proper ground bracing. It is likely that the plywood sheathing and the diagonal bracing to the walls is what is holding these trusses up.

7.4 Three Bracing Planes Top Chord Plane Bottom Chord Plane
Web Member Plane All truss systems, regardless of their shape must be braced along three planes. The top chord plane The bottom chord plane And the web member plane The three planes of bracing apply to both temporary and permanent bracing.

7.4 Bracing Basics Truss Members Lateral Braces Diagonal Braces
A simple way to brace any of these three planes is with lateral bracing. Lateral bracing runs in lines perpendicular to the truss down the length of the building. A line of lateral bracing should be placed at the center or peak of the truss and then at an on-center spacing as recommended in the bracing plan or guidelines. More about that in a minute. All lateral bracing, regardless if it’s temporary or permanent, needs to be restrained in some manner. The most common way of restraining lateral bracing is to use diagonal bracing installed along the same plane. The diagonal bracing stabilizes the system by creating triangulation, the same principle used in trusses! The BCSI series uses a color coded system for its illustrations. All wood truss members are shown in dark yellow. Lateral bracing is in dark green, And all diagonal bracing is in red. Truss Members Lateral Braces Diagonal Braces

7.5 Spacing of Top Chord Lateral Bracing
BCSI B2 contains this simplified graphic that shows top chord temporary lateral bracing and diagonals. The greater the length of the truss, the closer the rows of lateral bracing should be. The BCSI recommendations show lateral bracing spacings for trusses up to 80 feet, however any truss over 60 feet should be treated with special care. As mentioned earlier, refer to the TTB on Long Span Truss Installation for trusses 60 feet and greater in length.

7.5 Top Chord Lateral Bracing Options
Option A Option B Traditional industry recommendation New method in BCSI As far as the type of top chord temporary lateral bracing is concerned, the contractor has a couple options from which to choose. Option A: is what the truss industry traditionally has advocated. Option B: is a new method first introduced with BCSI.

7.5 Top Chord Option A Spacers on first five
Spacing per BCSI Spacers on first five Add Continuous Lateral Brace (CLB) Add diagonals Repeat spacers and CLBs on next four Repeat, adding diagonals every 20 ft Begin Option A with the first five trusses installed with spacer pieces. Once they are in place a continuous lateral brace can be applied at the same location. Then a set of diagonal braces are installed in the same plane. Install the next four trusses with the spacers, apply another continuous lateral brace and repeat adding a diagonal brace every 20 feet Until all the trusses are in place

7.5 Top Chord Option B Spacers on first five Add diagonals
Spacing per BCSI Spacers on first five Add diagonals Repeat procedure on groups of four trusses Until all trusses are in place Option B starts the same way as Option A, namely the first five trusses are installed and each is braced with spacers at the appropriate intervals. Once the first five are set, the diagonal braces are installed and the entire process is repeated on subsequent sets of four trusses, Until all the trusses are in place. Note there are no continuous lateral braces, but there are continuous diagonal braces.

7.5 Spacer Pieces The truss industry has traditionally discouraged the practice of using spacer blocks or short pieces for temporary truss bracing. Even so, framing crews routinely use them with varying amounts of success. When the truss industry developed BCSI, they understood that the practice of using spacer pieces was not going to go away so they developed recommendations for using short spacer pieces safely on the jobsite. The first type of spacer block is shown in Option 1. It is a top-nailed 2x4 that has a minimum length of 27 inches for trusses spaced at 24 inches on-center. These should be attached with two nails at each truss intersection and overhang by one-and-a-half inches on each side to prevent the piece from splitting. The second option shows end-grain nailed spacer pieces that are 22-and-a-half inches long and installed with the top surface flush with the top chord plane. The advantage to this method is that the pieces do not have to be removed, they can remain in place and perhaps even serve as blocking for the permanent roof sheathing. The third option is a steel spacer piece designed specifically for truss bracing. These proprietary products have different attachment methods depending on the manufacturer but they also can remain in place permanently. All of these three spacer options require continuous top chord diagonal bracing as we saw in the previous slide on Top Chord Option B if no continuous bracing will be used.

7.6 Alternatives to Temporary Bracing Options
Sheath early…sheath often An alternative to applying temporary bracing is to apply permanent sheathing immediately after four to five trusses are erected with spacers. Do not wait until all the trusses are erected before placing the sheathing.

7.6 Alternatives to Temporary Bracing Options
Built it on the ground. As mentioned previously as a safe option in fall protection, another option is to build the roof system on the ground. Install all permanent bracing and sheathing. And then lift the entire system in place. For large systems, make sure that the trusses are designed for the pick up point loads. Sheath it for stability. Pick it up. Set in place.

7.7 Bad Bracing Caught on Film!
In this section we will look at some common bracing mistakes made in the field and how they can produce disastrous results. This photo from a newspaper showcases the inappropriate use short spacer pieces of lumber.

7.7 Crew on Unbraced System
This is not the right way to install lateral bracing. The framer pictured is asking for trouble. He is crawling along the roof peak and installing the single lateral brace as he goes. Single lateral bracing alone is not enough temporary bracing to sufficiently secure the system, especially with the extra weight of the framer. It is also hard to maintain exact spacing with this practice.

7.7 No Diagonal Bracing No Diagonals
This is the type of bracing that is typically seen in the field. Notice: there is only one row of bracing on each side, the bracing does not lap by one truss space; it simply ends between the trusses, and the continuous lateral bracing is not stabilized with diagonally bracing

7.7 Spacer Pieces Only These trusses seem to have the correct lateral bracing down the middle of the top chord, but irregular spacer pieces are used near the heel and on the bottom chord. Some parts of the BCSI bracing recommendations are being followed, but not enough of either method to result in a complete and safely braced roof. In fact, there is no evidence of any diagonal bracing for those rows of lateral bracing. As mentioned previously, single lateral spacer pieces are not enough temporary bracing to sufficiently secure the system. This is a very dangerous practice to utilize these short pieces alone without diagonal bracing. Finally just to add some more excitement to the mix - a bunk of plywood was stored on top of the trusses. This is called a “construction load” which should only be applied to adequately braced systems. More on this later.

7.7 Killer Cleats This is how the lack of diagonal bracing when used with spacer block lateral bracing has earned the name “killer cleat”. Workers have been killed in truss collapses where the only bracing installed was spacer blocks. The blocks are a problem because when they don’t follow the minimum recommendations in BCSI, the trusses are very unstable and can rotate or buckle out of plane quite easily. Collapses like this can be avoided by following truss industry bracing guidelines in BCSI.

7.7 Removing Bracing There is only one row of temporary lateral bracing on a partially sheathed roof, which is insufficient for a truss of this length. As the installed sheathing extends up the roof to meet the bracing, the row or bracing can be removed. The sheathing is helping to prevent a buckling since it provides the stability of both the diagonal and lateral bracing. One good practice here worth mentioning is that the material they are using to sheath the roof is being held in place by a fork lift truck, rather than being set directly on the roof. This keeps the excess load off the partially braced roof.

7.7 No Bracing! This crew is working up inside a set of trusses as they are being installed. These trusses were too large to be shipped or manufactured in one piece so they were built in two pieces and have been field spliced at the center. There is no evidence of lateral or diagonal bracing on the top chord of these trusses, or anywhere else for that matter. The worker at the center is getting ready to install the next spacer block. This is a very dangerous way to install trusses - especially field-spliced scissors which are inherently top-heavy. The lives of these five workers are in jeopardy due to this dangerous installation practice.

7.7 No Diagonals This is the classic S-shaped curve that is present in trusses with insufficient bracing - trusses are laterally but not diagonally braced. Once the trusses buckle far enough out-of-plane, they can snap and the system can completely collapse. In the meantime, it most certainly can and will damage plate connections and joints beyond repair.

7.7 Results of Bad Bracing These trusses in this hip roof are severely buckling but stopped short of collapsing. There is some lateral bracing present, but as in the previous examples, there are few diagonals present. This allowed the whole system to shift. The fact that the trusses haven’t completely collapsed may be attributed to the partially sheathed roof.

7.7 Results of Bad Bracing This view of the same roof shows the top chords were inadequately braced and all the trusses started to bow out of plane before the remainder of the sheathing was installed.

7.7 Results of Bad Bracing This view from underneath illustrates how far the trusses have bowed out-of-plane.

7.0 Quiz

8.0 Permanent Bracing 1.0 Responsibilities 2.0 Guideline Documents
3.0 Job Site Storage 4.0 Handling 5.0 Installation 6.0 Fall Protection 7.0 Temporary Bracing 8.0 Permanent Bracing 9.0 Construction Loading The following section covers the topic of permanent bracing metal plate connected trusses.

8.1 Permanent Bracing References
The WTCA publications Commentary for Permanent Bracing of Metal Plate Connected Wood Trusses was written by industry Professional Engineer John Meeks in cooperation with the expertise of the Truss Industry Engineering Community. It provides guidelines for Building Designers to use in designing and specifying permanent bracing for metal plate connected wood truss systems. This 26-page document includes illustrations that help clarify key points.

8.1 Permanent Bracing References
Sections B3 and B6 from the BCSI series cover some valuable permanent bracing information but it is by no means the only permanent bracing required on trusses. An explanation of permanent bracing information and design responsibilities follows.

8.2 Types of Permanent Bracing
Responsibility of the Building Designer Three planes & web members if required Location is specified on Truss Design As mentioned previously, all 3 planes of a truss must be correctly braced both temporarily but also permanently. The Building Designer is responsible for specifying the permanent bracing for the entire structure and that includes the truss system. Truss designers indicate if any particular webs require permanent bracing but the transfer of loads from that bracing into the larger structural system are the responsibility of the Building Designer. The following are examples of how the three planes and the webs are braced permanently.

8.3 Top Chord Bracing Top Chord Plane
This example of a Truss Design Drawing highlights the top chord plane of a roof truss.

8.3 Top Chord Bracing Top chords of roofs are most often permanently braced with properly sized and fastened sheathing. This is the best way to provide stability in the two dimensional roof plane. The sheathing membrane is referred to as a roof diaphragm and acts like a thin, wide beam that can transfer loads from the roof into the side walls. It’s important to remember that the top chord sheathing is performing a crucial structural function and is not just there just for the benefit of the shingles.

8.3 Top Chord Bracing Sheathing is not rated for use in wide-on-center framing applications, generally over 48 inches on center. In these cases, the truss top chord is stabilized by regularly spaced purlins which act like permanent continuous lateral braces. But just like all other CLBs, they need to be tied off with diagonals and that is what is missing in this photo.

8.3 Bottom Chord Bracing Bottom Chord Plane
The bottom chord plane of trusses is generally in tension therefore buckling is not as large a concern as it is for top chords which are in compression. Bottom Chord Plane

8.3 Bottom Chord Bracing The application of gypsum board directly to the bottom chord creates a ceiling diaphragm and is usually sufficient permanent bracing for this plane.

8.3 Bottom Chord Bracing However, if trusses are located in areas where high wind uplift forces or large lateral load transfers are anticipated, lateral and diagonal bracing must also be installed in addition to the gypsum board ceiling diaphragm. This bracing should also be installed in applications where the gypsum board sheathing is not directly applied to the bottom chord such as with exposed bottom chords or suspended ceilings.

8.3 Web Plane Bracing Web Plane
The web plane bracing is also used to transfer lateral loads through the system. This bracing plane is often overlooked because there is no structural sheathing already in place like there is for roof and ceiling diaphragms.

8.3 Web Plane Bracing Web plane bracing collects loads that are generated from lateral forces on the gable end such as from wind, and transfers the load up into the roof diaphragm or down into the ceiling diaphragm. It has nothing to do with compression web bracing. It should terminate as close to the top and bottom chords as possible.

8.3 Web Plane Bracing This photo shows an installation
of web plane bracing at the gable end.

8.4 Web Member Bracing Locations
Some web members may require permanent bracing. If it is required, it will be specified by the Truss Designer on the individual Truss Design Drawings as shown. The marks on this particular drawing indicate that one line of continuous lateral bracing must be installed along the mid-point of the web. Webs that require permanent bracing are usually in compression.

8.4 Web Buckling The continuous lateral bracing shortens the effective buckling length of the identified compression webs. In order for this CLB to function properly it should be installed in a series of at least three adjacent identical trusses. The approximate location of this bracing on the braced web member is indicated on the Truss Design Drawings at either mid-point or one-third points. The Building Designer is responsible for determining the size, grade, and connection of this bracing to the web member, as well as the means of stabilizing this bracing to prevent the simultaneous lateral movement of the braced webs in the same direction.

8.4 Web Bracing The easiest way to stabilize permanent lateral bracing on web members is to install diagonal bracing at 20 foot intervals.

8.4 Web Bracing Diagonals This photo shows cross bracing installed to stabilize the line of continuous lateral bracing on a compression web.

8.4 Web Reinforcement T-Brace L-Brace Scab Brace Metal Reinforcement
If the truss layout does not have three of the same trusses in a row for lateral bracing, the buckling capacity of the web member can be enhanced by adding a T-brace. Technically, this is reinforcement rather than bracing. It will be specified by the Truss Designer on the Truss Design Drawing. Alternatives to the T-reinforcements are L-reinforcements, scab reinforcements and specially designed metal reinforcements.

8.5 BCSI B3 Web Bracing/Reinforcement
The B3 summary provides details on web member permanent bracing and reinforcement that must be installed in the field.

8.0 Quiz

9.0 Construction Loading 1.0 Responsibilities 2.0 Guideline Documents
3.0 Job Site Storage 4.0 Handling 5.0 Installation 6.0 Fall Protection 7.0 Temporary Bracing 8.0 Permanent Bracing 9.0 Construction Loading The following section covers the topic of construction loading of metal plate connected trusses.

9.1 Construction Loads Construction loading occurs when crews stack building materials like bundles of plywood or gypsum onto truss assemblies for temporary storage. Correct bracing is critical if you apply construction loads to trusses. Trusses have no capacity to carry load unless they are properly braced or sheathed. The B4 summary sheet describes the following do’s and don’ts about construction loading.

9.2 Load Only When Braced Never stack materials on unbraced or inadequately braced trusses. Trusses that are not properly braced may buckle or rotate. Only stack reasonable amounts of materials on properly braced structures.

9.3 Do Not Overload Trusses that are overstressed due to excessive construction loading will usually show excessive sagging or may show, in more severe cases, broken web or chord members or web members that have pulled out of their connector plated joints. Position the sheets flat with the longest edge perpendicular to the trusses and distribute the load over as many trusses as possible. Reasonable material stack heights vary by the material. Add only one stack of materials to one set of trusses.

9.4 Spread Load Around Spread the load over as many trusses as possible. Don’t overload single trusses or lean stacks against walls – they may not be braced for the load.

9.5 Place Loads Carefully Do not drop the materials on the truss assembly. An impact load is like doubling the material weight.

9.6 Do Not Load at Center Loads should be placed directly over structural supports like bearing walls, never in the center of a clear span.

9.7 Unstable locations Do not place loads on the ends of unsupported spans like cantilevers or on short trusses tying into girders.

9.8 Loads with No Bracing! What’s wrong with this picture? First, this roof system has some lateral bracing but no diagonals. It is inadequately braced. Yet it still is being loaded with extra weight from stacks of plywood. The same set of trusses is loaded with more than one stack of plywood. The materials are stacked at the center, not over the bearing supports.

9.9 Dangers of Overloading
When industry recommendations regarding construction material stacking are not followed, dangerous situations or even collapses can occur.

9.0 Quiz

BCSI Series For more info on: Truss repairs Girders Fall protection
Jobsite storage Truss handling Toe-nailing for uplift Temporary bracing Construction loading The BCSI series also covers topics like multi-ply girders, truss repairs and uplift reactions. Contact WTCA for sample copies of any of these documents.

Jobsite Safety Package
B1 through B4 Handling Checklist Preassembled JOBSITE PACKAGES contain summary sheets B1 through B4. Component Manufacturers can purchase them and add their own job documents for a comprehensive information package.

Truss Tags WTCA and TPI also offer truss tags that draw attention to installation and bracing issues in the field. All tags and BCSI summary sheets are now available in English and Spanish.

WTCA is the Information Source
Contact the Wood Truss Council of America for more information about the structural component industry. WTCA’s Mission Statement is to educate the building component industry to ensure the continued growth of components. This is accomplished through a variety of products and services geared toward its members and aligned building professionals.

Structural Building Components Magazine
The Structural Building Components Magazine promotes the knowledge and common interests of those engaged in manufacturing and distributing structural building components. SBC strives to be the industry’s information conduit by staying abreast of leading-edge issues. Contact SBC Magazine today to begin receiving your free subscription.

Our website is This gateway page provides links to the WTCA homepage, as well as other key organizations serving the industry. If you click on the WTCA logo…..

WTCA Homepage You will enter the home page of WTCA. You can view WTCA publications, order WTCA publications online, ask technical questions, look up manufacturers by state, view legislative issues, and much more.

Wood Truss Council of America wtca@woodtruss.com 608/274-4849
™ Thank you for your interest in the structural building components industry!

Presented by the Wood Truss Council of America

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