Crossbraces

Crossbraces are diagonal structural members designed to intersect between frames, typically forming an X shape between two vertical elements. They are used in timber and steel construction, as well as in scaffolding, lattice towers, and some bridges, to increase lateral rigidity and distribute horizontal loads.

By creating triangulated geometry, crossbraces resist racking and transfer wind, seismic, or other lateral forces toward the foundation and adjacent members. The crossing diagonals act in compression and tension, depending on load direction, while the joints at their ends transfer forces to the surrounding frame through pins, bolts, mortises, or welded connections.

Common configurations include X-bracing, where two diagonals cross and connect at their midpoints or at joints, and knee braces, which are shorter diagonals that reinforce corners. In timber framing, crossbraces may be mortised and tenoned or pegged; in steel construction they are typically bolted or welded with gusset plates.

Crossbracing provides stiffness with relatively low material cost and can be installed or altered without heavily increasing the frame’s size. It can limit interior space and complicate framing details. Materials range from timber to steel (and sometimes reinforced concrete in certain systems); steel crossbraces require corrosion protection and proper end connections.