What is a gusset plate?
A gusset plate (Dutch: schetsplaat or knoopplaat) is a plate of steel or timber that connects several structural members, creating a relatively stiff joint. Usually it joins chords, struts and diagonals that meet at one point, such as in a truss or a roof frame.
In steelwork the gusset is connected to the members by welding, bolting or, in older structures, riveting. In timber it is fixed with nails, screws or bolts. Plywood or solid timber gussets are commonly used to hold rafters together at the apex of a roof truss.
Why use a gusset plate?
In a truss, three or more members often meet at different angles. Connecting them directly to each other is awkward. The gusset provides a shared connection surface to which each member can be fixed separately, and the forces from the members are passed through the plate.
Application
Gusset plates are found in steel trusses and bridges, timber roof structures, wind bracing, connections of steel stairs to the main structure and many industrial buildings.
Points to watch:
- Structural design: plate size, thickness and the number and position of bolts or nails come from calculations. Always have gussets in a load-bearing structure designed by a structural engineer.
- Setting-out lines: make the centre lines of the members meet at a single point wherever possible, to avoid extra bending in the joint.
- Timber: keep enough edge distance for nails and screws to prevent splitting.
- Corrosion: protect steel gussets outdoors or in damp areas, for example by galvanising or a paint system.
- Don’t weaken it: never drill or cut into an existing gusset to run cables or pipes through.
Related Terms
- Truss
- Roof truss
- Nail plate
- Galvanising
- Structural engineer
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