The biggest change between ACI and CSA rebar detailing is the set of documents behind it. In the US, reinforcement is designed to ACI 318 and detailed to the ACI Detailing Manual and the CRSI Manual of Standard Practice, in inch-pound bar sizes. In Canada, it is designed to CSA A23.3, built to CSA A23.1, and detailed to the RSIC Manual of Standard Practice, in metric bars from 10M to 55M. The logic of a bar list or placing drawing is familiar either way, but bar sizes, grades, hook dimensions, bend diameters, cover and lap lengths all change. A US detail cannot simply be relabelled for a Canadian job.
This post is for detailers, engineers and contractors moving between the two systems. For the Canadian side on its own, see our guide to rebar detailing standards in Canada.
The two document sets side by side
| Role | United States | Canada |
|---|---|---|
| Design code for reinforced concrete | ACI 318 | CSA A23.3 |
| Construction requirements (hooks, bends, cover, placing) | ACI 318 and the project specification, often based on ACI 301 | CSA A23.1 |
| Construction tolerances | ACI 117 | CSA A23.1 |
| Detailing practice | ACI Detailing Manual (SP-66, including ACI 315) and the CRSI Manual of Standard Practice | RSIC Manual of Standard Practice (Fifth Canadian Edition, 2020) |
| Shop bending standard | ANSI/CRSI IPG5.1, which builds on ACI 318 bend limits | RSIC appendix hook and bend tables, built on CSA A23.1 |
| Bar material | ASTM A615 (carbon steel), ASTM A706 (low-alloy, weldable) | CSA G30.18 (400R, 500R, 400W, 500W) |
| Welding of rebar | AWS D1.4 | CSA W186 |
In Ontario, the building code calls up the CSA concrete standards by reference, so for permitted work A23.3 and A23.1 carry the force of the code. ACI documents can still turn up in specifications for particular products or test methods, but they are not the design basis for a Canadian building.
Bar sizes and grades
US bars are numbered by their nominal diameter in eighths of an inch: a #4 bar is 1/2 in (12.7 mm), a #8 is 1 in (25.4 mm). Canadian bars are named by their rounded nominal diameter in millimetres: 10M is 11.3 mm, 15M is 16.0 mm, 25M is 25.2 mm. No US bar is an exact match for a Canadian one. The full conversion is in our guide to Canadian vs US rebar sizes.
Grades differ as well:
- US: ASTM A615 bars come in Grades 40, 60, 80 and 100, where the number is the minimum yield strength in ksi. Grade 60 (about 420 MPa) is the everyday bar. ASTM A706 is the low-alloy bar used where welding or extra ductility is needed.
- Canada: CSA G30.18 bars are 400 or 500 MPa, with R (regular) or W (weldable) chemistry. 400W is the everyday bar in Ontario.
Hooks and bend diameters
This is where most conversion errors happen. The hook definitions look alike but the details differ.
Standard hooks:
| Hook | CSA A23.1 | ACI 318 |
|---|---|---|
| 90° standard hook | 90° bend plus at least 12 bar diameters | 90° bend plus 12 bar diameters |
| 180° standard hook | 180° bend plus at least 4 bar diameters, not less than 60 mm | 180° bend plus 4 bar diameters, not less than 2 1/2 in (64 mm) |
| Stirrup and tie hooks | 90° or 135° bend plus at least 6 bar diameters, not less than 60 mm | 90° hooks: 6 bar diameters (min 3 in) for #3 to #5, 12 bar diameters for #6 to #8; 135° hooks: 6 bar diameters, min 3 in |
CSA A23.1 also calls for stirrup and tie hooks to be 135° unless the concrete around the hook is restrained from spalling (that is the 2004 wording; check the edition your project uses). The engineer's drawings will show which hook applies.
Bend diameters are set differently. ACI 318 gives the minimum inside bend diameter as a multiple of bar diameter: 6 bar diameters for #3 to #8, 8 for #9 to #11 and 10 for #14 and #18, with 4 bar diameters for #3 to #5 stirrups and ties. CSA A23.1 lists a minimum diameter in millimetres for each bar size, and it depends on whether the bar is R or W grade. The RSIC tables built on A23.1 give these finished bend diameters for standard hooks:
| Bar | 400W or 500W | 400R or 500R |
|---|---|---|
| 10M | 60 mm | 70 mm |
| 15M | 90 mm | 100 mm |
| 20M | 100 mm | 120 mm |
| 25M | 150 mm | 150 mm |
| 30M | 200 mm | 250 mm |
| 35M | 250 mm | 300 mm |
Stirrups and ties are bent tighter in both systems, about 4 bar diameters for the small sizes. Our post on stirrup sizes and hook lengths gives the Canadian pin sizes.
Detailing allowances follow from all this. Here are the published 90° hook allowances (the A or G dimension added to the bar length) for the closest pairs of bars, from the RSIC tables for 400W bar and the CRSI fabrication standard:
| Canadian bar | 90° hook allowance | Closest US bar | 90° hook allowance |
|---|---|---|---|
| 10M (11.3 mm) | 180 mm | #4 (12.7 mm) | 8 in (203 mm) |
| 15M (16.0 mm) | 250 mm | #5 (15.9 mm) | 10 in (254 mm) |
| 20M (19.5 mm) | 300 mm | #6 (19.1 mm) | 12 in (305 mm) |
| 25M (25.2 mm) | 400 mm | #8 (25.4 mm) | 16 in (406 mm) |
The numbers are close for some pairs and not for others. That is exactly why a hook table from one system should never be used to cut bars for the other.
Cover, development and laps
Concrete cover. CSA A23.1 sets cover by exposure class and element, in millimetres: for example, 30 mm for beams and columns in class N (interior) exposure, 40 mm in the F and S classes, 60 mm in the C and A classes, and 75 mm for concrete cast against earth. ACI 318 sets its own cover values in inches by exposure and member type. They do not convert one to one, so use the Canadian table for a Canadian job. See concrete cover for rebar under CSA A23.1.
Development and lap lengths. Both codes use tension development lengths and Class A and Class B lap splices, but the equations and modification factors are different. A23.3's simplified method makes a Class B splice 1.3 times the development length. Do not take an ACI lap table, convert inches to millimetres and apply it to metric bars. Our lap splice length chart for metric bars shows the Canadian values.
Large bars. RSIC practice does not permit lap splices of 45M and 55M bars. They are joined with mechanical splices or by welding to CSA W186.
Detailing conventions and defaults
Both industries publish standard bar bend charts, bar list formats and default assumptions for when the drawings are silent. They are similar in spirit, but do not assume a US default carries over:
- Bend type codes. Check the shape sketch, not just the type number, when reading a bar list from the other system.
- Defaults. RSIC practice details stirrups 80 mm smaller than the beam when no size is given, assumes a 90° hook when none is specified, and gives bar lengths to the nearest 20 mm. A detailer working from US habits may apply different assumptions.
- Units on the drawings. Canadian placing drawings are fully metric. Mixed-unit drawings are a common source of field errors.
- Seismic detailing. Ductile and moderately ductile systems under CSA A23.3 have their own hoop, crosstie and seismic hook requirements. Seismic hooks in Canada use the RSIC seismic hook allowances, not the ACI values.
Converting a US design for a Canadian job
If a project arrives with US drawings, such as a building system designed south of the border or a repeat design from a US developer, a few steps keep it on track:
- The engineer of record resolves the design. Converting bar sizes changes steel areas and spacings, which is a design decision, not a detailing one.
- Detail in metric from the start. Set detailing software to Canadian bar sizes, the RSIC hook tables and the A23.1 bend diameters.
- Check every hook and bend allowance against the Canadian tables before bar lists are released.
- Confirm cover and lap tables with the engineer, using A23.1 and A23.3.
- Order to the Canadian grade called for, usually 400W, so bending and any welding follow Canadian requirements.
Detailing and fabrication to Canadian standards
We provide reinforcing steel estimates and detailing for reinforced concrete structures, then cut and bend 10M to 55M bar in our shop to the bar lists, tagged and bundled for your crew. If your drawings started life in the US, send them with the specification and we will flag what needs the engineer's attention before anything is fabricated.
Request a quote with your drawings, or see our rebar products for straight, fabricated and GFRP bar.
Frequently asked questions
Is ACI 318 used in Canada?
Not as the building code. Canadian building codes, including the 2024 Ontario Building Code, call up CSA A23.3 for concrete design and CSA A23.1 for construction. Canadian detailers follow the RSIC Manual of Standard Practice rather than the ACI Detailing Manual or the CRSI manual.
Are ACI and CSA hook lengths the same?
The basic geometry is close: both use a 12 bar diameter extension on a 90° standard hook and a 4 bar diameter extension on a 180° hook. The minimum extensions, bend diameters and stirrup hook rules differ, and the bars themselves are different sizes, so hook dimensions are not interchangeable.
What is the ACI rebar detailing manual?
The ACI Detailing Manual (SP-66) collects ACI's detailing guidance, including ACI 315, for presenting reinforcement on design and placing drawings. In the US it is used with ACI 318 and the CRSI Manual of Standard Practice. The Canadian counterpart is the RSIC Manual of Standard Practice.
Can I use US rebar on a Canadian job?
Only if the engineer of record approves the substitution. US bars are a different set of sizes and grades from Canadian 10M to 55M bar, so areas, spacings, laps and bend dimensions all have to be rechecked.
