Trusses...anything wrong here?

[Mark S. Tyson]

Originally Posted by jfunderburk

Can you quote that section please. Give the context...the section heading too. Thanks.

Joe,
Your testing my typing skills but at any rate here is the complete quoted text of the section

BCSI edition published 2006
pg. 39

Permanent Bracing For The Bottom Cord Plane

Permanent Bracing for the bottom cords of metal plate connected wood trusses is typically provided by attaching either gypsum wallboard or continuous lumber lateral restraint properly braced against lateral movement

Lateral restraint shall be applied in combination with diagonal bracing spaced at intervals along the length of the building or other means that will provide stability and transfer the forces from the lateral restraint to a lateral force resisting system

Lumber used for lateral restraint and/or diagonal bracing shall be stress rated

Bottom chord permanent lateral restraint shall be installed at the spacing indicated on the TDD and/or by the building designer with a maximum of 10' on center

The TDD provides information on the assumed support for the bottom chord based on the load conditions for which the truss has been designed. This typically includes a directly applied rigid ceiling or Lateral Restraint at a specified maximum on center spacing

[Kenton H. Shepard, CMI]

Originally Posted by mtyson

Kenton,
...When referencing the manual it states that Bottom cord Permanent Lateral Restraint shall be installed at the spacing indicated on the TDD and or by the Building Designer with a maximum of 10' on center.

What's TDD?
Also if the trusses have been designed and signed off on by a building designer, doesn't that negate any need for compliance with the TDD?

[Kenton H. Shepard, CMI]

Originally Posted by mcyr

Bracing

There are two types of lateral bracing used in truss construction, temporary and permanent. Temporary bracing holds the trusses vertical during construction.
Permanent bracing is used where required by the engineering analysis. The type and location of required bracing is indicated in the information provided by the truss manufacturer to the field when the trusses are delivered to the job site.

BCSI-B1 SUMMARY SHEET
Guide for Handling, Installing and Bracing of Metal Plate Connected Wood Trusses

General Notes

Trusses are not marked in any way to indentifiy the frequency or location of temporary bracing. Follow the recommendations for handling, installing and temporary bracing of trusses. Refer to BCSI 1-03 Guide to Good Practice for Handling, Installing & Bracing of Metal Plate Connected Wood Trusses for more detailed information.
Truss Design Drawings may specify locations of permanent bracing on individual compression members. Refer to the BCSI-B3 Summary Sheet - Web member Permanent Bracing/Web Reinforcement for more information. All permanent bracing design is the responsibility of the Building Designer.

Permanent bracing is clearly shown on any shipment drawings supplied by the Manufacturer upon delivery.

If permanent lateral bracing is not observed in an attic, they were either not specified by the Manufacturer, or the bracing was omitted, and the tags showing location of the bracing were torn off on purpose.


http://www.woodtruss.com/projects/woodtruss/bcsi.php

I think Marcel's got it (black text my addition).

[Mark S. Tyson]

Originally Posted by kshepard

What's TDD?
Also if the trusses have been designed and signed off on by a building designer, doesn't that negate any need for compliance with the TDD?

TDD, Truss Design Drawing
Excellent point the sign off used to be a big gray area in that the TDD and the actual construction documents were submitted to the building department as separate documents.
If memory serves correctly that loop hole was eliminated with the Florida code cycle in 1997 and now requires the Building Designer to review and sign each sheet of the TDD acknowledging acceptance
Then with the code cycle of 2001 they finally got it right. Typically the TDD will only provide the reaction pressures that the trusses must be braced for such as uplift and lateral movement and not the method for bracing or attachment. Now the building designer must include all reaction, bracing, and the method of attachment, the connector manufacturer, and the size and number of nails to be used and must include that information on the plan view of the roof plan
So currently at least here in Florida all attachments and permanent bracing is included on the actual blue print with the exception of the permanent bracing for the web plane which is still the responsibility of the Truss Designer

[Marcel R. Cyr]

Works the same way here Mark. For Commercial, anyways.

Residential, the lumber yard sends the truss Manufacture the size of the house and their in-house engineers design the system.
Everything required is on the TDD.