Attachment Of Scissors Trusses
Question:
What is the correct method of attaching scissors trusses to the top plate? I read recently in a trade magazine that this type of truss should be toe-nailed on one end and attached with slotted clips on the other end. According to the article, this is to allow for movement of the truss. We require PE stamped spec sheets from the truss manufacturer to verify trusses meet wind and snow loads. These sheets give bracing requirements but never give recommended attachment requirements.
Answer:
The attachment requirement information is never on the stamped truss design drawing because the truss designer's responsibility does not cover truss-to-bearing connections (see section 2 of the Truss Plate Institute's ANSI/TPI 1 or section 3 of SBCA’s TTB – Standard Responsibilities in the Design and Application of Metal Plate Connected Wood Trusses, IBC 2015 2303.4.4 or IRC 2015 R802.10.1). The truss design drawing will only list the expected horizontal deflection. It is up to the building designer (P.E. or architect of record) to determine how to design the structure to accommodate this deflection. The connection method you describe is certainly one possibility. (For more information regarding this connection read Considerations in Specifying a Connection for Horizontal Movements by Charles C. Hoover, Jr., P.E.)