Diaphragm Basics - The Analysis of Irregular Shaped Structures - page 45

F i g u r e 2.19 Alternate detailing—parallel to shear wall.
There is no guarantee of where the trusses will fall with respect to the wall location
unless a specific truss layout pattern is shown on the drawings, or an additional truss is
called out to be installed directly over the shear wall. Figure 2.17 shows three widely
used typical details that cover most of the likely truss locations placed adjacent to the
wall. Configuration A shows the condition where the shear wall falls at any location
between two trusses. Shear is transferred through special nailing of the diaphragm
sheathing into the collector truss. Occasionally plywood sheathing is applied to the face
of the truss so that the collector forces are transferred through the sheathing similar to
a shear panel or shear wall and not as a truss. Consideration needs to be given to attic
ventilation and other code requirements for this condition. In some cases, it may be pos-
sible to incorporate a sheathed truss with a code-required draft stop. The bottom chord
of the truss is typically nailed into the end grain of the flat blocking over the wall with
two 16d common nails. The flat blocking is typically spaced at 24″ o.c. and is nailed to
the top plate of the shear wall with four 16d common nails. Calculations verifying the