Reinforcing Steel (Rebar)
CSA G30.18-21 rebar sizing, metric designations, Grade 400W/500W, lap splices, mechanical splices, tie wire, rebar chairs, and concrete cover requirements.
- Interpret CSA G30.18-21 metric rebar designations and grade markings
- Explain Grade 400W and 500W weldable rebar and carbon equivalent requirements
- Calculate lap splice lengths and describe mechanical splice types
- Identify proper tie wire patterns, chair types, and cover requirements
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Rebar Basics & Sizing Designations
Canadian Rebar Standard - CSA G30.18-21
In Canada, reinforcing steel is governed by CSA G30.18-21. Canadian specifications use a metric designation system where the bar number represents the approximate cross-sectional area in mm2 divided by 100. The four most common bar sizes are:
CSA Metric vs Imperial Bar Designations
Canadian drawings specify metric CSA bars (10M, 15M, 20M, 25M). The imperial #4, #5, #6, #8 system is a US ASTM designation not used on Canadian project specifications. When the Red Seal exam references Canadian construction, expect metric CSA designations.
CSA Rebar Grade Designations
Under CSA G30.18-21, the modern Canadian grades and their "W" suffix are critical to understand:
| CSA Grade | Yield Strength | "W" Designation | Notes |
|---|---|---|---|
| Grade 400W | 400 MPa min | Weldable | Modern standard - restricted carbon equivalent |
| Grade 500W | 500 MPa min | Weldable | High-strength - restricted carbon equivalent |
| Grade 300 | 300 MPa min | Not "W" rated | Virtually eliminated from Canadian supply chains |
The "W" suffix means Weldable - the steel has a restricted carbon equivalent formula that prevents the formation of brittle martensite in the heat-affected zone (HAZ) during welding. Grade 300 is no longer specified on modern Canadian projects. Both Grade 400W and 500W are the current standard.
Grade 400W (Modern Standard)
400 MPa minimum yield strength
Weldable - restricted carbon equivalent
No brittle martensite in weld HAZ
Most common Canadian specification
Grade 500W (High-Strength)
500 MPa minimum yield strength
Weldable - restricted carbon equivalent
Used where reduced bar congestion is needed
Increasingly common in modern structures
Grade markings are rolled into the bar surface and include the mill symbol, bar size (10M, 15M, etc.), and grade mark (one line = 400W, two lines = 500W on the deformation pattern).
Canadian rebar follows CSA G30.18-21 with metric designations (10M, 15M, 20M, 25M). The "W" suffix means Weldable with a restricted carbon equivalent that prevents brittle martensite in weld heat-affected zones. Grade 400W is the most common modern Canadian specification. Grade 300 is virtually eliminated from current supply chains.