tvärstag

A tvärstag is a diagonal or transverse bracing element used in architecture and engineering to resist lateral forces and prevent deformation of a rectangular frame or structure. The term is Swedish, with tvär meaning across or transverse and stag meaning stay or brace.

In timber framing and in walls made of brick or masonry, tvärstag typically takes the form of a diagonal wooden beam, steel strut, or steel cable that connects opposite members such as studs, plates, or rafters. The bracing can be arranged as an X with two crossing diagonals or as a single diagonal brace, and it is usually fixed with metal connectors, bolts, or anchors.

Materials vary, including wood for traditional constructions and steel or steel cables for modern work. The choice depends on load requirements, environmental conditions, and whether the brace primarily resists tension or compression. In many bracing systems, diagonals operate in tension to resist shear, though configurations can be designed to carry compression when necessary.

Applications include timber-frame houses and other buildings that require stiffening against wind or seismic loads, as well as various framed structures where maintaining a rectangular geometry under load is important. Tvärstag may also be used in roof bracing and in other assemblies where lateral stability is essential.

Design and installation considerations include ensuring the brace is properly rated for its intended forces, correctly anchored, and installed so as not to introduce undesirable stresses into connected members. Adequate detailing for fastening and potential corrosion protection is important for long-term performance.

See also: cross-bracing, diagonal bracing, tie rod.