Concrete Column Tie Spacing: What the Rule Says

How far apart can the ties in a concrete column be? Two engineering summaries give the same three-way limit, one citing ACI 318-11 and one citing ACI 318-19. This article walks through that limit, checks it by hand, and says plainly what it cannot confirm.

What Limits Column Tie Spacing?

The smallest of three numbers caps the spacing between ties, according to two summaries of ACI 318. STRUCTURE magazine (Jerod G. Johnson, Ph.D., SE, September 2014) describes the ACI 318-11 Chapter 7 provision as 16 vertical bar diameters, 48 tie diameters, or the least column dimension. The ideCAD help page, which summarises ACI 318-19, gives the same three limits for center-to-center spacing.

This article keeps the two editions apart, even though the summaries match. CalcNote, a small calculator site, repeats the 318-19 limits and calls itself a secondary summary, so it counts as corroboration only. Each column gets its own answer, because bar size, tie size and column size change which of the three limits is smallest.

Nothing here is a design. The concrete column calculator counts concrete volume only, and it sizes no ties or bars.

How Do You Work the Spacing Out by Hand?

Find 16 times the bar diameter, 48 times the tie diameter and the least column dimension, then take the smallest. A bar’s diameter in inches is its bar number divided by 8, which is this article’s arithmetic and not a source figure. So #3 is 0.375 in, #4 is 0.500 in, #5 is 0.625 in and #6 is 0.750 in.

These checks are arithmetic on the summarised rule, not designs. All three use #3 ties, which the ideCAD summary pairs with bars of #10 or smaller. The tie limit is 18 in each time because the tie is the same: 48 x 0.375 = 18 in.

1. #4 bars, #3 ties, 12 in column. 16 x 0.500 = 8 in; 48 x 0.375 = 18 in; least dimension 12 in. The least is 8 in.
2. #5 bars, #3 ties, 16 in column. 16 x 0.625 = 10 in; 48 x 0.375 = 18 in; least dimension 16 in. The least is 10 in.
3. #6 bars, #3 ties, 14 in column. 16 x 0.750 = 12 in; 48 x 0.375 = 18 in; least dimension 14 in. The least is 12 in.

What Do Tie Size and Bar Support Add?

The ideCAD summary of ACI 318-19 adds a minimum tie size and a bar-support rule on top of the spacing limit. It pairs a No. 3 tie with No. 10 or smaller longitudinal bars. It pairs a No. 4 tie with No. 11 or larger bars or bundled bars. For bar numbering, see our guide to rebar size numbering.

The same page says every corner bar and every alternate bar needs lateral support from a tie corner with an included angle of not more than 135 degrees. It also says no unsupported bar may sit farther than 6 in clear, on each side along the tie, from a supported bar. CalcNote repeats both points for 318-19.

A Concrete International abstract (DeGagne, Erdogmus and Savage, 2016) states the 6 in rule as well. It says the requirement dates from the 1963 Code and that the clear spacing limit was apparently based on the experience of committee members. The sources read state the rule, not how to detail it.

Do Earthquake Rules Change Tie Spacing?

Yes, STRUCTURE says the seismic provisions can change the answer. It calls the ACI 318-11 Chapter 21 provisions far more complex than Chapter 7 and says they may require a much tighter spacing, “typically not more than 6 inches”.

The magazine article is titled as a question, “Do ACI Seismic Provisions Apply?”

This article gives no other seismic figure. It also cannot confirm hook rules for ordinary ties. The 135 degrees in the support rule is an included angle at a tie corner, not a hook angle. Look for seismic notes on the drawings before applying the ordinary limit.

Who Sets the Spacing on a Real Job?

The project drawings or a structural engineer set it, and local code governs small residential piers. That is a recommendation to follow the plans, not a sourced rule. A web page cannot see your plans, your code edition or your seismic category, which is why this article stops at the summarised rule.

Our guide on when a wall needs an engineer makes the same point for walls. Other structural concrete calculators cover volumes for related members.

What Does the Column Calculator Count?

It counts concrete volume for round or square columns, and ties and bars come from the drawings. Its own example is four 12 in round columns, 9 ft tall, with 10% waste. The calculator page gives an 80 lb bag a yield of 0.60 cu ft, and says reinforcement, size and load capacity come from a code or an engineer.

• One column. Area = pi x 0.5 x 0.5 = 0.7854 sq ft; x 9 ft = 7.0686 cu ft.
• Four columns. 7.0686 x 4 = 28.27 cu ft; x 1.10 for waste = 31.10 cu ft.
• Yards and bags. 31.10 / 27 = 1.15 cu yd; 31.10 / 0.60 = 51.8, so 52 bags of 80 lb.

FAQs About Column Tie Spacing

Sources and Further Reading

Tie spacing is set by the code edition and the drawings for your column, so follow your plans or ask an engineer. The rules here are secondary summaries, and ACI 318 itself was not read. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated 2026-10-21.