Information about truss bracing

[Pete Daly]

Can anyone refer me to a source for information regarding the industry standards for permanent bracing of factory trusses?

Thanks,

Peter Daly

[Bruce King]

It depends............

This should get you started..........
Trusses...anything wrong here? - InterNACHI Message Board (http://www.nachi.org/forum/f23/trusses-anything-wrong-here-53736/)

[Darren Miller]

Trusses 'usually' have marking on them stating "permanant bracing here".

[John G. Vetter]

Can anyone refer me to a source for information regarding the industry standards for permanent bracing of factory trusses?

Thanks,

Peter Daly

Here in Florida each set of trusses comes with the engineers sheet for the individual truss and they have small squares or rectangles on the web or chord where bracing is necessary. You can't use generic specs and try to make a determination if it is suppose dto be braced or not. If you have web and gable ends that are longer than or higher than 5' it's a good bet that there should be bracing in the form of a diagonal or continous brace.

[Jerry Peck]

If you have web and gable ends that are longer than or higher than 5' it's a good bet that there should be bracing in the form of a diagonal or continous brace.

Along with a strong back across the inside face of the gable end studs.

If the gable studs are higher than (typically) 8', then the upper portion will have a diagonal brace and a strong back, with an intermediate strong back and diagonal brace for it.

"Typically" ... because as John said, it is all in the engineering and that is what you have to go by.

[David J. Smith]

Engineered trusses attic or floor come with an installation plan. Each system is custum engineered and the bracing will be different. Different manufacturers while similar may have different requiremnets. I inspect for generally accepted good practice but I also have a disclosure that states it is not possible to inspect a truss system without the original engineer's plans.
Truss manufactuers have their installation guide lines avaiable on line, some examples
Quality Floor I-Joists, The Original TJI Joist from iLevel - Trus Joist (http://www.ilevel.com/floors/f_TJI_joists.aspx)
http://mirkostrade10.sydneyinstitute.wikispaces.net/file/view/pryda+roof+truss+guide.PDF
The Canadian CMHC has a general guide line for engineered floor systems.

[Steve Frederickson]

As others have said, you need to see the engineering, but here's a great link for general information:

Building Component Safety Information (http://www.sbcindustry.com/bcsi.php)

[Mark Cramer]

Can anyone refer me to a source for information regarding the industry standards for permanent bracing of factory trusses?

Thanks,

Peter Daly

Truss roof systems require 2 separate types of bracing. This issue is lost on most people in the construction industry.

1. Some individual webs of individual trusses need bracing. This is the responsibility of the truss engineer.

2. The ENTIRE truss system needs permanent bracing to hold the trusses in their original positions when forces are exterted on the building, such as wind or seismic forces. The design of this bracing is the responsibility of the building designer, i.e., architect or engineer. I would venture to say that 99.9% of existing buildings lack this bracing, even though it's spelled out clearly in truss industry documents and has been for years.

The building codes have some language like this:

The design and manufacture of metal-plate-connected wood roof and floor trusses shall comply with ANSI/TPI 1.

This document (in chapter two) states:
2.2.2 As this Standard does not cover the design for the complete structural system of a building, the Building Designer shall provide for the following in the design and detailing of the building:
(a) Truss deflections
(b) Truss movement due to moisture and temperature change
(c) Truss supports and anchorage accommodating horizontal, vertical or other reactions or displacements.

Item (c) above comprises permanent bracing and restraint of lateral bracing. This typically involves 3 things, top and bottom chord bracing and X bracing across the plane of the webs. The top chord bracing is achieved by sheathing. Bottom chord bracing usually consists of rat runs.

Here is some language from HIB-91 which explains this clearly. I just wrote a letter regarding this last week, so I have this handy:

13.2 PERMANENT BRACING
Permanent bracing is designed and specified by the architect or engineer for the structural safety of the building. It is the responsibility of the building designer to indicate size, location, and attachments for all permanent bracing a required by design analysis. In general, it is desirable to design and locate all bracing so that it may work together with other structural parts of the building (such as shear walls, portal frames, bearing walls, columns, beams, etc.) to achieve total structural integrity.
Permanent bracing should provide sufficient support at right angles to the plane of the truss to hold every truss member in that position assumed to for in the design. In addition permanent bracing should be designed to resist lateral forces imposed on the completed building by wind or seismic forces.



13.2.3.2 PERMANENT DIAGONAL BRACES

Permanent diagonal bracing in the plane of the web members is also used to distribute unequal loading to adjacent trusses and to spread lateral forces to diaphragms or shear walls. Spacing of rows of permanent diagonal bracing in the plane of the webs is a matter of the building designer’s judgment and will depend upon the truss plan, truss configuration, type of building, and the loading. Generally for pitched roof trusses, the spacing ranges from 12 to 16 feet, depending upon how it relates to the bracing in the plane of the top court. . .

Figures 37, 38 and 39 illustrate permanent bracing in the plane of webs.




In my market (FL), almost every house is engineered. The engineer specifies permanent bracing on the plans. (See attachment.) Most contractors have no idea what that spec means until it's explained to them.

Search for ANSI/TPI 1-2002 and BCSI 1-03 for additional documentation.

Here are a couple more documents you can find that help explain all of this:
Wood Truss Bracing, Dr. Frank E. Woeste, P. E.

What Every Architect/Engineer (A&E) Should Know about Metal Plate Connected Wood Floor/Roof Trusses, John E. Meeks, P. E.

[Robert Koen]

Heres something I had saved it may help.

[John Dirks Jr]

As others have said, you need to see the engineering, but here's a great link for general information:

Building Component Safety Information (http://www.sbcindustry.com/bcsi.php)


Ditto! This document is extensive.