Canadian rebar sizes: 10M to 55M, weights per metre and how to order

Canadian structural drawings call for bars by their metric size: 3-15M CONT. in a strip footing, 10M @ 400 E.W. in a slab. The supplier sells them by weight. The takeoff in between is simple once you have the table: count the metres, add the laps the drawings ask for, and multiply by the mass per metre.

The sizes, 10M to 55M

These are the CSA G30.18 bar sizes used across Canada. The “M” number is close to the bar's diameter in millimetres, and the area is the round number the engineer designs with.

The most common in houses and low-rise work are 10M and 15M. Commercial footings, walls and columns add 20M and 25M, and the big sizes (35M to 55M) turn up in heavy columns, transfer beams and bridges.

What one bar weighs

Suppliers in Ontario stock bars in 6, 12 and 18 m lengths, and 10M and 15M also come in coil. What a single bar weighs matters for handling and for checking a delivery ticket:

Grades

CSA G30.18 bars come in grades 400 and 500, which is the yield strength in megapascals, with a letter: W for weldable and R for regular. 400W is the everyday bar in Canada. The grade is on the drawings' general notes. It doesn't change the weight, but it does change the price and the bar you order, so it belongs on the takeoff.

Reading a US spec: the nearest ASTM bar

US drawings and product literature use inch-based bar numbers (#3, #4, #5…). The nearest match by area is below. That's for reading a US document, never for swapping one bar for another. A substitution is the engineer's call.

A worked example: a strip footing

A strip footing 40 m long with 3-15M CONT., bought in 12 m bars. The laps come from the drawings: say the structural notes give 650 mm for 15M. Your job will have its own figure, so use that.

1. Laps along one run: 40 m ÷ 12 m = 3.33 → 4 bars, so 3 laps
2. One run with laps: 40 + 3 × 0.65 = 41.95 m
3. All three bars: 41.95 × 3 = 125.85 m
4. Weight: 125.85 m × 1.570 kg/m = 197.58 kg, about 0.20 tonnes
5. Pieces to order: 125.85 ÷ 12 = 10.49 → 11 bars of 12 m, before cut-offs

Then add what the straight run leaves out: corner bars and bends where footings meet, dowels up into the wall, and any bars shown in section but not in plan. Each is its own line, with its own count.

What gets missed

• Laps. On a long run of 10M or 15M, laps can add several per cent to the steel. Count them per run, not as a flat allowance.
• Both ways. E.W. (each way) and T&B (top and bottom) double the bars, and T&B E.W. quadruples them.
• Dowels and hooks. Their lengths are on the drawings or in the bending schedule. They're short, but there are a lot of them.
• Accessories. Chairs, bolsters and tie wire aren't rebar, but they come off the same takeoff.

Doing it on the drawings

In PreConstruct AI a concrete type carries its bars: continuous bars with laps in a footing, bars each way in a slab or pad, verticals and ties in a column. Every length you measure becomes metres of each bar and then kilograms, pounds or tonnes, with the arithmetic printed on the line. The bar sizes, spacings and laps are the ones on your drawings. It counts and measures, and never sizes or designs the steel.