Rebar Stirrups vs Ties: What Is the Difference?

Stirrups and ties are both bent bars that wrap around the main reinforcement, but they do different jobs in different members. Stirrups go in beams, grade beams and similar horizontal members, where they resist shear and hold the top and bottom bars in position. Ties go in columns, piers and other compression members, where they hold the vertical bars in place, stop them from buckling outward and confine the concrete. They are bent from the same bar sizes, often 10M, so a closed stirrup and a column tie can look identical on the truck. What makes one a stirrup and the other a tie is the member it goes in and the job it does there.

Stirrups vs ties at a glance

What stirrups do in a beam

When a beam carries load, the concrete near the supports is stressed in diagonal tension. Without reinforcement across that path, diagonal cracks can open and the beam can fail suddenly in shear. Stirrups cross those potential cracks and hold them closed. That is why stirrups are usually spaced closest near the supports, where shear is highest, and further apart toward mid-span.

Stirrups also:

• Carry torsion in spandrel and edge beams, where the drawings call for closed stirrups.
• Support the top bars at the right height and hold the bottom bars down onto their chairs.
• Tie the cage together so it can be assembled, lifted and set as a unit.

Open U-stirrups are common in beams cast with a slab, where the slab steel closes the top. Closed stirrups are used where torsion, seismic detailing or the design calls for them, sometimes as a U-stirrup with a separate cap tie across the top for easier placing.

What ties do in a column

A column's vertical bars are in compression. Long, slender bars in compression want to buckle outward, and if they do they push off the concrete cover and the column loses capacity quickly. Lateral ties wrap the vertical bars at regular intervals and stop that.

Ties also confine the concrete inside them. Confined concrete can carry more strain before it crushes, which gives the column more ductility. In members designed for seismic ductility, the ties become hoops: closed ties with seismic hooks, at tighter spacing in the regions expected to yield.

CSA A23.3 sets the minimum size and maximum spacing of column ties based on the size of the longitudinal bars, the tie bar size and the column's dimensions, and it requires corner bars and certain intermediate bars to be held in the corner of a tie or by a cross-tie. Our post on stirrup spacing in beams and columns goes into the spacing rules, and the structural drawings always govern.

Spirals

Round columns and piles often use a spiral instead of individual ties: one continuous helix wrapped around the vertical bars at a set pitch. Spirals give excellent confinement and are detailed by diameter, pitch and the number of turns, with extra turns at the ends. On drawings they appear as "SPIRAL" with a pitch, rather than as ties at a spacing.

Why people mix up the terms

The confusion is understandable:

• Same shapes, same sizes. A closed 10M rectangle could be a beam stirrup or a column tie. Only the drawing tells you which.
• Regional terms. Some regions and older drawings call both of them "links", and site crews often say "stirrups" for anything bent into a loop.
• "Tie" means three things. A lateral tie is a bent bar in a column. Tie wire is the annealed wire used to fasten bars together at intersections, which has no structural role once the concrete is placed. And a tie bar in pavement work is a deformed bar holding two slabs together at a joint (see dowel bars vs rebar).
• "Rebar vs stirrups." Stirrups are rebar. They are bent from the same deformed bar as the main reinforcement, usually in smaller sizes.

When you read a bar list, the bar mark and the member it is tagged to are what matter. A detailer will usually give beam stirrups and column ties different marks even when the shapes are the same, so bundles are not swapped on site.

Hooks and shapes

Both stirrups and ties end in hooks that anchor them into the concrete core. Standard stirrup and tie hooks are 90° or 135°, and seismic hoops need 135° hooks with longer extensions. The hook type, bend diameter and extension length depend on bar size and the design. Our post on stirrup sizes and hook lengths covers the dimensions, and our guide to ordering custom stirrups covers out-to-out sizing.

Common shapes:

• Beam stirrups: open U, closed rectangle, U with cap tie, and multi-leg stirrups for wide beams.
• Column ties: closed rectangles or squares, with cross-ties (single bars with hooks on both ends) or diamond ties to restrain intermediate bars in larger columns.
• Pier and pile reinforcement: circular ties or spirals.

Getting them right on site

Most problems with stirrups and ties are placement errors, not fabrication errors:

• Spacing drift. Stirrup spacing changes along a beam. Mark it out from the support, not by eye.
• Ties left out at the top and bottom of columns, where the drawings often show closer spacing at beam-column joints and at splices.
• Hooks in the wrong place. Alternate the hook positions around the column where the drawings call for it, and keep hooks anchored into the core rather than the cover.
• Wrong marks swapped. A beam stirrup and a column tie of similar size are not interchangeable if their dimensions or hooks differ.
• Cover. Stirrups and ties are the outermost bars, so their position sets the concrete cover. See our post on concrete cover.

Sizes and spacings for stirrups and ties come from the structural design. If you are unsure what the drawings call for, ask the designer before ordering.

Order stirrups and ties bent to your drawings

We fabricate stirrups, ties, cross-ties and custom bent shapes in the shop, tagged by mark and member so they go straight to the right beam or column. We also prepare bar lists and placing drawings from your structural drawings. Send us your drawings for a free take-off and quote, or see our rebar products.