All modern building codes reference a Truss Placement Diagram, which “identifies the proposed location for each individually designated truss and references the corresponding truss design drawing” (IBC 2021, 2303.4.2). This is typically accomplished via a top-down view of the structure, a truss ID labeling the shape that represents each truss, and a dimension that locates each truss relative to the building’s edge. The purpose is to guide the installation of the trusses.
The diagram is typically not the primary source for engineering information like how the trusses are designed or how they are to be anchored. Truss Placement Diagrams are merely a supplement to or summary of information found in the Truss Design Drawings. If they aren’t referencing information like that from a sealed document, they should be sealed themselves.
The Truss ID label may contain the hardware that should be used to connect each end of the truss to its bearings, i.e. hangers and/or nails. In this example, an index is used that references a table nearby.
Graphics like this indicate hanger connections:
Key features of the roof will often appear so they can be used for reference when orienting the diagram and locating the trusses. This includes, but is not limited to, openings in the frame for a skylight or chimney, dormers, a projection of the roof showing slope changes, and portions of the framing that will be built on-site.
Some of the most pertinent information for installing trusses may be called out in a Truss Placement Diagram. This includes things like heel details, special truss-truss connections, and the locations of valley sets and piggyback trusses. Girder trusses typically receive their own dimension lines indicating their “setback” from a parallel edge of the building.
Do you have questions about a project but don’t have a structural framing layout yet? Save time by letting us design a truss placement diagram for you based on the construction documents for the project. Don’t have construction documents? We can design layouts from scratch too.