Figure 3-22. Truss layout
g. Assembly. Assembling a truss after it has been cut and bored is simple. In most cases,
timber connectors are used where different members of the truss join. Assemble the truss with the split
rings in place. The bolts are then placed in the holes and tightened. Place washers at the head and nut
ends of each bolt. Use straight, sound timber trusses (see Figure 3-23).
Figure 3-23. Split rings on a truss
3-8. Purlins. Purlins are used in roof construction to support corrugated sheet metal if it is used or
to support the sheathing of roofs famed with trusses. In small roofs, short purlins are inserted between
the rafters and nailed through the rafters. In large buildings where heavy trusses are used, the purlins
are continuos members that rest on the trusses and support the sheathing. In small buildings, such as
barracks, mess halls, and small warehouses, 2 by 4s are used for purlins, with the narrow side up (see
Figure 3-24, page 3-18).