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OBC DIVISION B · PART 9 · SECTION 9.40 — REINFORCED CONCRETE SLABS

What reinforcement and concrete requirements apply to suspended slabs in Ontario houses?

Suspended slabs need reinforcing steel sized and spaced for the span and load, positioned with proper concrete cover, adequate slab thickness and bearing at supports, and durable concrete, with air entrainment and higher strength where exposed to vehicles and de-icing salts.

Code reference
Reinforced slabs spanning over openings or spaces must contain reinforcement appropriate to the span, support conditions and imposed loads, placed with sufficient cover to protect against corrosion, in concrete meeting the strength and durability provisions of the Code, including exposure-class requirements for garage floors subject to freeze-thaw and chlorides. End bearing on supporting walls must be adequate.
OBC Division B, Section 9.40.

Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.

What this means in practice

Placement is where these slabs succeed or fail: in a simple span the steel belongs in the bottom third with cover maintained, and bars walked down into the mud or left sitting on the forms do nothing. Garage exposure demands air-entrained concrete at the higher strength classes the Code assigns to salt-exposed surfaces, commonly 32 MPa territory, and honest curing. Detail the slab-to-foundation bearing and any door openings carefully, and slope the surface to drain. When spans, cantilevers or loads exceed prescriptive scope, the slab becomes a Part 4 engineered element with sealed drawings.

Plain language

The steel bars inside a suspended concrete slab are its skeleton; they must be the right size, in the right position, with enough concrete covering them so road salt cannot rust them. Salt-exposed garage slabs also need tougher, air-entrained concrete.

Related questions

When do the reinforced concrete slab rules apply, such as garage slabs over basements, in Ontario?

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This page is provided for general information. Building code requirements depend on your specific project, occupancy and municipality, and code editions change. Always verify requirements against the current Ontario Building Code and confirm with your local building department.