What is a tension rod?
A tension rod, also called a tie rod or tie bar, is a relatively slender bar that resists tensile forces: it stops building parts from being pulled apart or spreading outwards. Because a bar in tension cannot buckle, it can be much thinner than a strut carrying the same force in compression. Tension rods are usually hot-dip galvanised steel or stainless steel. In Dutch it is called a trekstaaf or trekstang.
Uses
- Roofs and trusses: a rod between the feet of two rafters, or between the supports of an arched truss, resists the outward thrust so the walls are not pushed out. In timber trusses this member is the tie beam.
- Churches and historic buildings: iron tie rods across a nave or between arches hold vaults and walls together. On the outside you will often see a wall anchor plate.
- Wind bracing: crossed tension rods in the walls and roofs of steel-framed sheds and warehouses provide stability against wind.
- Canopies: a raking tie rod holds a canopy back to the facade.
- Glass facades: thin stainless steel rods are used to stabilise structural glazing and curtain walls against wind.
- Reinforced concrete: the reinforcing bar that carries tension is sometimes also called a tension bar.
Components and adjustment
- Rods can be extended and tensioned with a turnbuckle or coupler with left- and right-hand threads.
- Ends are often fitted with forks (clevises), eyes or anchor plates.
- A tension rod is usually lightly pre-tensioned so it does not sag and works immediately.
Practical tips
- Never just remove one: in old buildings tie rods sometimes look redundant but can be vital for stability. Always have a structural engineer look before removing or cutting one.
- Rust: a rusting tie rod in a wall expands and can crack the masonry. Check anchor plates and rod ends for corrosion.
- Tensioning: do not tighten a turnbuckle “by feel”; too much pre-tension can damage the connections.
Related terms
- Facade anchor rod
- Cavity wall tie
- Truss
- Reinforcement
- Transverse arch
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