The plies of girder trusses must be connected together adequately to provide proper distribution of loads between plies. Nailing size and pattern used in two or more plies girder are shown on engineering drawings and in TPIC Design Manual Tables( B.1, B.1.2, B.1.3, B.1.4 and  B.1.5). 

 

Attaching together 4 or more plies girder requires the use of bolts + Nuts + Washers.

The size of bolts and pattern must be calculated by qualified authorities. 

The reduction in the lumber size due to the use of bolts, will result in the reduction of the lumber capacity. For four or more plies girder trusses, it is strongly recommended that all web members to be minimum 2X4 SPF#2/#1 lumber or better and the Combined Stress index (CSI) of of girder truss members which are attached together with one row of  1/2" bolts to be less than: 

               0.85 for all 2X4 members

               0.88 for all 2X5 members

               0.90 for all 2x6 members

               0.92 for all 2x8 members

               0.94 for all 2X10 members