Originally Posted By: phinman
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Roof truss installation requires temporary and permanent bracing. As an old carpenter contractor and roof truss designer the blocks shown in your photo are very time consuming to install especially if you have a crane setting there during the installation! Although not in your photo blocks nailed in between trusses can serve as nailers for roof sheathing where trusses with “built up valleys” are used. Of course they should not be removed.
Here in Jersey most guys cut 25 1/2" blocks to space the trusses. This is typically lath. For large trusses this can be very dangerous and not a recommended practice by the Wood Truss Council. Some guys use lengths of 2x4,s with (2) 12d nails in each truss which is preferred, fast and safe. Sometimes it is possible to end up using this as the permanent bracing if permanent bracing is called for in a location suitable for temporary bracing also.
Temporary bracing as stated earlier can safely be removed but is often left in place.
Permanent bracing, often called lateral bracing, should never be removed and is an integral part of the truss design. Permanent bracing is typically installed on a truss web that is in compression and terminates at a spot where the lateral loads can be transferred to the framing below. Sometimes there are shear walls present to accept the load but you would not be able to see them after the all finishes have been installed.
It is really IMPOSSIBLE to inspect the trusses without the truss placement plan, each truss plan and the architects plan which will incorporate any of the load transfer from the trusses to the main structure.
When inspecting an attic I look for bowed members which would indicate missing lateral bracing, splice plates that have pulled away from the truss, split webs and cords, adequate gable end bracing, cords or webs that have been drilled or cut by the trades and proper vents to allow air from the soffits into the attic. As some one else stated tags and paint marks sometimes are put on the truss to show where permanent bracing is required. Permanent bracing should overlap on 2 trusses.
Some hardware is sometimes visible such as sheathing clips and hangers on girders. The hangers must have all nail holes filled to support the load for which is was designed.
For phased inspections tread lightly if you do not have all the information! There are no set rules and each designer may treat conditions differently. One may use a paralam while another a girder truss to support a span.
If you have exposed framing with trusses the bottom cord must be braced every 10 on center. Often you will see this bracing in attics on the bottom cord but generally are not part of the permanent bracing requirements. Most truss programs will not require this bracing if the is drywall attached to the bottom cord. The drywall serves as the lateral bracing for the bottom cord.
In conclusion truss construction is technically difficult especially with the larger homes and commercial buildings. We generally as home inspectors have none of the technical data available to us to inspect the trusses properly. Trusses should NEVER be cut and trussed attics should not be used for storage unless designed to the additional loads.
I hope I was of some help!
Phillip R. Hinman