Do Footings Need Rebar? Ontario Building Code Rules

For a typical Ontario house, the Building Code does not require rebar in plain concrete strip footings that fall within Part 9. Subsection 9.15.3 of the 2024 Ontario Building Code (O. Reg. 163/24) sets how wide, how large and how thick a footing must be, but says nothing about reinforcement. Rebar becomes mandatory when the footing is outside Part 9's scope and has to be designed, or when the drawings your permit was issued on call for it.

That short answer hides most of what matters on a real job, so here is how the rules work and when you should expect bars in the trench.

What the 2024 Ontario Building Code says about footings

The 2024 OBC came into force on January 1, 2025. It adopts the National Building Code of Canada 2020 with Ontario's amendments, so the Part 9 numbering now follows the national code. If you learned the rules from the 2012 OBC, check the article numbers again before quoting them.

For footings, the relevant part is Subsection 9.15.3 of Division B. In plain terms it requires:

• Footings where needed (9.15.3.1). Footings go under walls, pilasters, columns, piers, fireplaces and chimneys that bear on soil or rock. They can be omitted under piers or monolithic concrete walls only if the soil or rock can safely carry the load.
• Good support (9.15.3.2). Footings must sit on undisturbed soil, rock or compacted granular fill.
• Minimum widths and areas (9.15.3.4 and Table 9.15.3.4). These depend on how many floors the footing supports, whether it is under an exterior or interior wall, and for columns, the column spacing. Masonry construction above adds width (9.15.3.5 and 9.15.3.6).
• Minimum thickness (9.15.3.8). At least 100 mm, or the width of the footing's projection beyond the wall or column it supports, whichever is greater.
• Step footings (9.15.3.9). Each vertical rise is limited to 600 mm and each horizontal run must be at least 600 mm.

The concrete itself must meet Section 9.3. For footings, that means a 28-day compressive strength of at least 15 MPa under Article 9.3.1.6, unless something else in Part 9 asks for more.

Read the whole subsection and you will not find a bar size, a bar count or a spacing. Part 9 treats a footing inside its limits as a plain concrete element whose job is to spread load onto soil that can take it. Its width does that job, not reinforcement.

When Part 9 footing rules stop applying

The Part 9 footing tables only cover a defined set of conditions. Under Article 9.15.1.1, they apply to concrete footings that are not subject to surcharge, on stable soils with an allowable bearing pressure of 75 kPa or more, under buildings of wood-frame or masonry construction, or flat insulating concrete form (ICF) buildings of not more than 2 storeys with a floor-to-floor height of no more than 3 m.

Outside those conditions the footing has to be designed instead of picked from a table. The code calls this out in several places:

• Filled ground, peat or sensitive clay. Footing sizes must be designed under Section 4.2 (Sentence 9.15.1.1.(3)). The code specifically includes Leda clay in its definition of sensitive clay, which matters in parts of eastern Ontario.
• Joist spans over 4.9 m. Sentence 9.15.3.3.(2) sends these to Section 4.2, with an alternative formula in 9.15.3.4.(2) for widening strip footings under light wood-frame buildings.
• Floor live loads over 2.4 kPa. Footings must be designed under Section 4.2 (Sentence 9.15.3.3.(3)).
• Soils weaker than 75 kPa, surcharged walls and other cases that do not match 9.15.1.1. These go to Section 9.4, which requires design to good engineering practice or to Part 4.

Once a footing is engineered, rebar is normally part of the design. The engineer decides the bar size, number, spacing, cover and laps based on the loads and soil, and those details appear on the structural drawings.

Other places you will see rebar at the footing

Even when the strip footing itself is plain concrete, the walls sitting on it can bring steel into the footing:

• ICF foundation walls. Under Article 9.15.4.4, one of the ways a flat ICF foundation wall can be treated as laterally supported at the bottom is by dowelling it to the footing with 15M bars spaced not more than 1.2 m apart, or 10M bars spaced not more than 600 mm apart. A shear key, or limiting the backfill to 1.2 m, are the other options.
• Reinforced concrete block walls. Where Table 9.15.4.2.-B requires vertical bars in a block foundation wall, Sentence 9.15.4.2.(4) says they run from the top of the footing to the top of the wall, with at least 50 mm embedment into the footing where the slab doesn't provide lateral support at the base.
• Column pads and piers. Pad footings under steel or wood posts are sized by area under Table 9.15.3.4, but heavier point loads, such as the posts under a new beam where a bearing wall was removed, are often designed by an engineer and reinforced. See our guide to prefabricated rebar cages for footings and piers.

The foundation wall rules have their own tables and spacing requirements, covered in detail in foundation wall rebar in Ontario.

Why many footings get rebar even when the code doesn't ask

Concrete is strong in compression and weak in tension. A strip footing on even, undisturbed soil is mostly in compression, which is why Part 9 lets it be plain. Real sites are rarely that tidy, and designers often add a few continuous longitudinal bars because they:

• Help bridge local soft spots. A pocket of loose soil, an old service trench or a backfilled stump hole under one part of the footing makes that section bend. Bars carry the tension that would otherwise crack it.
• Control crack width. Shrinkage and settlement cracks still happen, but reinforcement keeps them tight and stops them from opening into a weak plane.
• Tie the footing together. Continuous bars through corners and steps make the footing act as one element, which helps limit differential settlement between parts of the house.
• Make additions and steps behave. Where a new footing meets an old one, or where a footing steps down a slope, dowels and continuous bars keep the pieces working together.

The bars themselves are a small part of the cost of a foundation, which is why "put two bars in it" is a common habit. Just keep in mind that adding bars does not let you shrink the footing. Width and thickness still have to meet Table 9.15.3.4 and Article 9.15.3.8, or the designer's numbers.

Drawings decide, and the inspector checks

The most practical rule is this: whatever is on the permit drawings is what has to be built. If the drawings show plain footings, plain footings are acceptable. If the drawings show two continuous 15M bars, the bars are a permit condition, not a nice-to-have.

Division C of the code requires the permit holder to notify the building department of readiness to construct footings, and again when footings and foundations are substantially complete before backfilling (Sentence 1.3.5.1.(2)). That first inspection is when an inspector can see the trench, the bearing soil and any reinforcement before concrete covers it. Pouring before the inspection, or without the steel shown on the drawings, is one of the more expensive mistakes on a small job, because the remedy may be exposing or replacing work that is already done.

If you're a homeowner planning an addition, garage or underpinning, a qualified designer or engineer prepares the footing design and the building department reviews it. Footings are structural work, so don't size or detail them yourself from an article. This post explains what to expect, not how to design.

Getting the bars right when they are required

When your drawings do call for reinforcement, the details that cause trouble on site are predictable:

• Size and count. 10M and 15M are the most common sizes in house footings, but the drawings govern. Our rebar sizes chart shows how the metric sizes compare.
• Concrete cover. Bars need minimum cover so they don't corrode, and cover against soil is larger than cover inside a building. The requirements come from CSA A23.1. See concrete cover for rebar.
• Laps and corners. Continuous bars are spliced by overlapping them, and corners need bent bars or corner bars so the reinforcement is continuous around the footing. Lap lengths come from the design.
• Support. Bars must be held at the right height with chairs or supports, not laid on the soil and lifted during the pour.

For a closer look at sizing and quantities, read rebar for footings, which walks through how to estimate how much bar a footing takes.

Order footing rebar cut, bent and tagged

If your drawings show reinforcement in the footings, piers or walls, send them to us and we'll prepare a bar list and quote. We detail, cut and bend 10M to 55M bar, including corner bars and dowels, and tag each bundle to the drawings so your crew isn't sorting steel in the trench. See our rebar products for straight bar, fabricated shapes and GFRP.