Rebar for Footings: Size, Quantity and Ontario Code

There is no single code-mandated rebar size for house footings in Ontario. When a footing is reinforced, the bar size, count and spacing come from the designer's or engineer's drawings, and on houses that usually means 10M or 15M continuous bars. What the 2024 Ontario Building Code does set is the size of the footing itself, which in turn controls how long the bars are and how many fit.

Whether a footing needs rebar at all is a separate question, covered in do footings need rebar. This post assumes your drawings call for it and walks through sizes, layouts and quantities.

Start with the footing size

Bars are sized to fit the concrete, so the footing dimensions come first. For footings within Part 9, Table 9.15.3.4 of the 2024 OBC (O. Reg. 163/24) sets these minimums:

Adjustments that commonly apply to Ontario houses:

• Exterior walls get 65 mm more width for each storey of masonry veneer over wood frame, 130 mm for each storey of masonry construction and 150 mm for each storey of flat ICF wall (9.15.3.5).
• Interior masonry bearing walls get 100 mm more for each storey of masonry supported (9.15.3.6).
• Column pads for spacings other than 3 m are adjusted in proportion to the column spacing (9.15.3.7).
• Thickness must be at least 100 mm or the footing's projection beyond the wall, whichever is greater (9.15.3.8).
• Water table: on gravel, sand or silt with the water table closer than the footing width below the bearing surface, widths and areas double (9.15.3.4.(3)).

These are minimums for stable soil of at least 75 kPa bearing capacity, supported joist spans up to 4.9 m and floor live loads up to 2.4 kPa. Outside those limits, footings are designed and the engineer sets both the dimensions and the steel.

What size rebar for footings: 10M or 15M

On reinforced house footings the choice is almost always between two sizes:

A 15M bar has twice the steel area of a 10M bar, so two 15M bars carry roughly what four 10M bars would. Designers weigh a few things when they pick:

• How much steel is needed. Longer spans over soft spots, heavier loads and wider footings push toward 15M or more bars.
• Footing width and cover. Bars need minimum concrete cover on every side, which limits how many fit across a narrow footing.
• Laps and bends. Larger bars need longer lap splices and larger bend diameters, so a 15M corner bar is a bigger shape than a 10M one.
• Consistency. Many drawings use 15M throughout footings and walls so there's one size to handle on site.

Storey count doesn't map to a bar size. A two-storey house needs a wider footing than a bungalow under Table 9.15.3.4, but whether that footing gets two 15M bars, three 10M bars or none is a design decision. For other sizes, see our Canadian rebar sizes chart.

How footing rebar is laid out

Reinforced footings show up on drawings in a few standard arrangements:

• Strip footings: continuous longitudinal bars running the length of the footing, often with short transverse bars at a set spacing in wider footings. The longitudinal bars do most of the work bridging soft spots.
• Corners and intersections: bent L-shaped corner bars or lapped hooks so the reinforcement is continuous around the building. Without them, every corner is a break in the steel.
• Pad footings under columns: a mat of bars in both directions near the bottom of the pad, sometimes called "bars each way". Heavier pads may have a second mat, or a prefabricated cage.
• Step footings: bars bent or lapped through each step, which is limited to a 600 mm rise and a 600 mm minimum run under Article 9.15.3.9.
• Dowels: short bars cast into the footing that project up into the wall. ICF and reinforced block walls use these, and their spacing comes from the wall design.

How to calculate rebar for a footing

Here's a worked example for a simple rectangular house. These bar counts are for illustration only; your drawings set the real ones.

Assume: a footing perimeter of 44 m, drawings showing two continuous 15M bars, four corners, and four interior column pads each detailed with four 10M bars each way, 800 mm long.

1. Continuous bars: 44 m x 2 bars = 88 m of 15M.
2. Laps: count the splices. If bars are delivered in lengths shorter than each wall run, every joint needs a lap of the length shown on the drawings. Add each lap length to the total.
3. Corner bars: two bent corner bars per corner (one per bar line) x 4 corners = 8 corner bars. Add their developed length, measured along the bend.
4. Pads: 4 bars x 2 directions x 0.8 m = 6.4 m of 10M per pad, so 25.6 m for four pads.
5. Weight: 88 m x 1.570 kg/m = 138.2 kg of 15M before laps and corners. 25.6 m x 0.785 kg/m = 20.1 kg of 10M for the pads.

Then add the laps, corner bars and dowels from steps 2 and 3. On a real footing plan with steps, bump-outs, a garage and a porch, those extras can make up a meaningful share of the total, which is the main reason rough calculations come up short.

Rebar calculators vs a detailed bar list

Online rebar calculators are fine for a ballpark weight. They tend to miss the details that decide whether you have enough steel on site:

• Laps, which depend on bar size, concrete and design, not a fixed rule of thumb. See the lap splice length chart.
• Corner bars, hooks and bends, which use more length than a straight line suggests.
• Steps, pads, piers and dowels, which are usually shown in details rather than on the main plan.
• Cut lengths. Each bar is cut to a mark on the drawings rather than from a generic stock length, so waste depends on how the job is detailed.

A rebar detailer works from the drawings and produces a bar list: every bar mark with its size, quantity, length and bend shape. For a deeper look at estimating methods, see rebar calculator and estimating.

Ordering footing rebar so it shows up right

Footings are usually the first concrete on a job, so a late or wrong delivery holds up everything after it. A few habits help:

• Order from the issued drawings, not a preliminary set. Footing changes after review are common.
• Ask for bars tagged to their marks. Tagged bundles mean the crew places corner bars at corners and pad mats at pads without measuring every piece.
• Phase deliveries if footings, walls and slab are poured weeks apart, so steel isn't sitting in the mud.
• Confirm site access for the delivery truck, especially on infill lots.

Our guide on how to order cut-and-bend rebar covers bar lists, tags and delivery in more detail.

Get a footing bar list and quote

Send us your footing and foundation drawings and we'll prepare a take-off and quote, then detail, cut, bend and tag the bars to your marks. Deliveries can be phased to match your pours. See our rebar products for straight bar, fabricated shapes and dowels.