1. Four Steps to Safe Truss Installations™
Presented by the Wood Truss Council of America

2. Most Truss Collapses Are Caused By….
Inadequate Temporary Bracing

3. 4 Steps to Safe Truss Installations
Storage & Handling
Temporary Bracing
Construction Loading
Fall Protection
Outline of the topics that will be covered in this Truss Technology Workshop.
Job Site Storage & Handling
Temporary Bracing
Construction Loading
Fall Protection

4. Jobsite Package Truss Documentation ‘HIB’ Guides
Handling, Installing & Bracing
The pre-assembled WTCA/TPI jobsite package contains summary sheets B1 through B4.

5. BCSI-B1 Summary Sheet Guide for Handling, Installing & Bracing of Metal Plate Connected Wood Trusses
The BCSI-B1 Summary Sheet lists the “do’s and don’ts” of wood truss handling, installation and bracing. It features illustrations instructing the builder on proper techniques for unloading, storing, lifting, erecting, and bracing trusses. This Summary Sheet replaced the HIB-91 Summary Sheet and the WTCA-B1 Warning Poster. And is a joint WTCA/TPI document.

6. Step 1 – Metal Plate & Banding Warning
Care should be exercised when removing banding to avoid damaging trusses and injuring workers.

7. Step 1 - Jobsite Storage Keep off the ground
To avoid distorting the plane of the trusses and collecting moisture from the ground, trusses that are to be stored on site for an extended time should be stored flat, on level grade, and on blocks.
From the B1 Summary Sheet:
These trusses are being stored with blocking holding them up off the ground that is spaced correctly at the 8 to 10 feet on center as recommended.

8. Step 1 - Long Term Storage
Trusses should not be allowed to pick up excess moisture during storage. However, wrapping them tightly in plastic like here may do more harm than good.
A better solution would be to drape the cover over loosely to allow air flow but prevent exposure to rain or snow.

9. Avoid Long Term Exposure

10. Step 1 - Storage Conditions
This is a job site storage condition that is NOT recommended and is potentially dangerous. Because they are unbalanced, these trusses are a danger to anyone that is working around them.
This photo illustrates how trusses can scatter out like a deck of cards when the bands are broken.

11. Step 1 - Handle with Care

12. Step 1 - Hoisting

13. Step 2 - Bracing
Purpose of Bracing: To apply sufficient support at right angles to the plane of the truss so as to hold every truss member 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 while they are being temporarily braced. This fastening and temporary bracing must hold trusses in position until permanent roof sheathing is installed. Temporary bracing must be capable of resisting the loads from the weight of the workers involved in the erection process, as well as the loads necessary for stability that all structures are expected to resist until permanent bracing has been installed. Trusses are not marked in any way to identify the frequency, or location of temporary erection bracing.
In Section 1, we learned that triangles make trusses strong...triangles also make bracing strong.

14. Trusses are very strong in their own plane if they are installed plumb and vertical.

15. Can’t Support Lateral Loads
Once loads are applied out of the plane of the truss, it becomes unstable.
This is why truss bracing is so important to good truss performance.

16. Step 2 - Ground Bracing
It is important to provide substantial bracing for the first truss erected.
The B1 Summary Sheet describes this process,
The best way to do this is to brace to the most stable element available – the ground.
The remaining trusses rely upon the first truss for stability.
Thus, the performance of the truss bracing system depends to a great extent on how well the first truss is braced.
Notice that the ground bracing uses the principle of triangulation to increase stability.
Also notice that each line of lateral bracing on the top chords lines up with a vertical ground brace.

17. Step 2 - Bracing Three Planes
Bracing needs to be applied to three planes on the truss:
the top chord plane,
the bottom chord plane
and through the web plane.
These trusses have temporary bracing applied to each of the three bracing planes. A completely braced plane will have
continuous lateral braces (in green)
stabilized with diagonal braces (in red). The B1 Summary Sheet applies to trusses spaced at 24 in. on center or less. Bracing material should be 2x4 grade marked lumber at least 10 feet long and overlapped one truss space.
Lateral Brace
Diagonal Brace

18. Step 2 – Top Chord Plane
Next let us look closer at the top chord plane.
Here is a demonstration with continuous lateral braces
stabilized with diagonal braces.
When the diagonals are installed under the top chord, they do not have to be removed before sheathing the assembly.
ALWAYS Stabilize Lateral Braces with Diagonal Braces

19. Insufficient Top Chord Bracing
There should be
A lateral brace at the peak
and one close to the heel
and all lateral braces should be stabilized with diagonal braces.
There is only one row of continuous lateral braces on this set of trusses. This is insufficient for this span.

20. Spacer Pieces & No Diagonals!
Can Lead to Compression
Buckling of the Top Chord
Notice what happens when the top chords are inadequately braced with spacers.
The trusses started to bow out of plane before the sheathing was installed.

21. Top Chord Temporary Bracing with Spacers
This diagram shows how to install a complete top chord temporary bracing system using short spacer pieces as the continuous lateral braces and diagonals.
This is taken from the B1 Summary Sheet.
Notice this is also the same diagram shown in the B2 Summary Sheet.

22. Step 2 - Floor Truss Bracing
Lateral Brace
Diagonal Brace
Floor trusses do not require as much bracing as parallel chord trusses due to floor trusses being assembled in the 4x2 direction. They inherently are more stable,
but they still must be braced laterally and diagonally.

23. Bowing or Tilting?
These trusses are fully sheathed on one side but the other side is ineffectively braced.
The result is that the system is still bowing out of plane.

24. Step 2 – Sheathing Sheathe early & often
One option is to sheath with plywood/OSB immediately after four to five trusses are erected. This will obviously be done in increments of four, six, and eight feet to accommodate offsetting the sheathing end joints.
Do not wait until all the trusses are erected before sheathing is placed.

25. 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.
Notice that there is no lateral bracing on the top chord of the trusses. 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.
What we would like to know is who will volunteer to be the worker in the center of the picture on their next truss installation job.

26. 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 laterally, they can snap and the system can completely collapse. In the meantime, it most certainly can and will damage plate connections and joints.

27. Results of Bad Bracing
The top chords were inadequately braced and all the trusses started to bow out of plane before the sheathing was installed.

28. Results of Bad 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
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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 here.

29. Results of Bad Bracing
Here is another view of the previous roof. A rope tied to a tractor is being used to prevent the trusses from any further buckling
– ‘tractor bracing” is not very effective.
B10 covers more information on wide on-center spaced trusses.

30. Step 2 - Bottom Chord Bracing
The bottom chord plane of trusses is generally in tension and compression buckling is not as large a concern as it is for top chords which are in compression.
Bottom Chord Plane

31. Step 2 - Bottom Chord Bracing

32. Step 2 - Bottom Chord Bracing

33. Step 2 - Web Plane Bracing
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.

34. Step 2 - Web Plane Bracing
Temporary web plane bracing helps with the stability of the system, but if it is well thought out it can easily remain in pace and become permanent bracing.

35. Gable End Bracing
Like this gable end bracing shows. Refer to BCSI-B6 for more information on gable end frame bracing.

36. Step 2 – Permanent Web Bracing Locations
Compression Web Bracing
In addition to the permanent bracing of the three planes, 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.

37. Step 2 - Web Buckling
The continuous lateral bracing serves to shorten 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.
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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 so as to prevent the simultaneous lateral movement of the braced webs in the same direction.

38. Step 2 - Web Bracing
The continuous lateral bracing serves to shorten 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.
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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 so as to prevent the simultaneous lateral movement of the braced webs in the same direction.
B3 explains how important web bracing is to the structural integrity of individual components. The colorful graphics and photos help installers understand the correlation between information provided on Truss Design Drawings and the web member permanent bracing that must be installed in the field.

39. Step 2 - Web Reinforcement
T-Brace
L-Brace
Scab Brace
Metal
Reinforcement
The buckling capacity of a web member can also be enhanced by adding a T-brace. This type of bracing is generally used when dissimilar trusses are located next to each other.
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When this occurs, the braced compression webs often do not line up, making continuous lateral bracing very difficult if not impossible to install. Since this type of bracing is specific to an individual truss, the size and type of brace, as well as the connection to the web, will be specified by the Truss Designer on the Truss Design Drawing.
Alternatives to the T-Brace are L-braces, scab braces and specially designed metal reinforcements. For more information on web reinforcement, refer to the TTB on this topic.

40. Step 3 - Construction Loads
During the construction phase of a structure, <animate>
trusses must often support the weight of both workers and building materials.
Construction loading is the term used to describe these loads.
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A common example arises when builders stack bundles of plywood or gypsum onto truss assemblies for temporary storage. Bracing is critical if you apply construction loads to trusses. Trusses have no capacity to carry load unless they are properly braced.
How much is too much? This document answers the question by giving the safe and reasonable stack heights for materials that we saw earlier. It gives recommendations for
good load placement on flat and pitched trusses,
what sort of construction loading practices to avoid,
and urges the user to make absolutely sure that no loads are placed unless the truss assembly is properly braced or sheathed.

41. B4 Loading DOs and DON’Ts
Never Stack Materials on Unbraced or Inadequately Braced Trusses. As seen in the previous slides, trusses that are not properly braced may buckle or rotate.
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Only stack reasonable amounts of materials on properly braced structures.

42. B4 Loading DOs and DON’Ts
Never Stack an Unreasonable Amount of Material on the Trusses.
[Animate]
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. Sheetrock or gypsum board should be a maximum of 12 inches high. Plywood or OSB panels should be a maximum of 16 inches high, asphalt or composite shingles should be place in bundles of two or less, and concrete block should only be placed on floor systems in a single layer. Also only add one stack of materials to one set of trusses.

43. B4 Loading DOs and DON’Ts

44. B4 Loading DOs and DON’Ts
B4 Construction Loading replaces the Truss Technology in Building Brochure by the same name.

45. B4 Loading DOs and DON’Ts

46. Loads with No Bracing!
Several groups of plywood are scattered out on this roof system that has some lateral bracing but no diagonals. Also the same set of trusses is loaded with more than one stack of plywood.
<animate>
this is very dangerous. <animate>. Only stack materials along outside supports or directly over inside supports of properly braced structures.

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

48. Step 4 - Fall Protection
A single truss is NOT designed to withstand loads from a falling person.
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A single truss, if used as an anchorage point, can pull all the trusses on top of a falling person.
Depending on how the entire building is braced, incorrect fall protection attachments could cause an entire building collapse.
In all cases, the person faces the increased risk of causing a serious truss collapse.
B11 explains graphically how trusses are not designed to be fall protection anchors. It then presents several tips for framing crews to safely and efficiently install trusses while meeting OSHA’s Fall Protection Guidelines.

49. Step 4 - Fall Protection
A falling worker attached to a single truss may cause the trusses to “domino”
A single truss is NOT designed to withstand loads from a falling person.
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A single truss, if used as an anchorage point, can pull all the trusses on top of a falling person.
Depending on how the entire building is braced, incorrect fall protection attachments could cause an entire building collapse.
In all cases, the person faces the increased risk of causing a serious truss collapse.

50. Step 4 – Pre-Assemble Units
Built it on the ground.
Sheath it for stability.
A safe option in fall protection, another option is to <animate> built the roof system on the ground <animate> with sheathing in place and <animate> then lift the entire system in place. Obviously, make sure that the trusses are designed for the pick up point loads.
Pick it up and set in place.

51. Step 4 - Scaffolding Personal fall arrest system to OSHA guidelines
Option 2: Use a scaffolding system with personal fall arrest system following OSHA’s guidelines if necessary .

52. Step 4 – Scaffolding?
Not like this!

53. Step 4 - Roof Peak Anchors
Sheath and brace a portion of roof and install a roof anchor to OSHA guidelines
Option 3: Sheath and brace a portion of the roof and use a roof anchor, following OSHA’s guidelines. If you are uncertain, contact OSHA or a design professional for assistance.
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Roof anchors are attached to the truss and only 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.

54. BCSI Series For more info on: Truss repairs Girders Fall protection
Jobsite storage
Truss handling
Toe-nailing for uplift
Temporary bracing
Construction loading

55. WTCA is the Information Source
WTCA serves the Structural Component Industry by providing key information to its members and aligned building professionals. 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.

56. Structural Building Components Magazine
The mission of Structural Building Components Magazine (SBC) is to increase the knowledge of and to promote the common interests of those engaged in manufacturing and distributing structural building components. Further, SBC strives to ensure growth, continuity and increased professionalism in our industry, and to be the information conduit by staying abreast of leading-edge issues. Contact SBC Magazine today to begin receiving your subscription!

57. www.woodtruss.com Our website is www.woodtruss.com. <animate>
Woodtruss.com takes you to an introductory page that provides links to the WTCA homepage, as well as other key aligned organizations serving in our industry.
<animate> If you click on the WTCA logo…..

58. 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.

59. Wood Truss Council of America wtca@woodtruss.com™
Wood Truss Council of America
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