Question 1

What concrete strength does Ontario's Code set for a garage floor?

Accepted Answer

Section 9.3.1.6(1) of Ontario's 2024 Building Code sets a minimum compressive strength of 32 MPa after 28 days for garage floors and carport floors. That same section also covers all exterior flatwork, so the 32 MPa figure applies across those categories. For interior floors other than garages and carports, the minimum is 20 MPa, and for all other applications it is 15 MPa. A few related Code requirements bear on a garage slab.

Question 2

My Stittsville garage floor slopes toward the house: what now?

Accepted Answer

A garage floor that slopes toward the house instead of toward the door is a drainage problem the 2024 Ontario Building Code directly addresses. Section 9.35.2.2 requires that where an attached or built-in garage is provided, the garage floor shall be sloped to drain liquids to the outdoors. A floor that drains toward the house is not what that clause describes, so it is worth having assessed. Before deciding on a fix, have a contractor assess a few things.

Question 3

Who should break out an old garage floor in Gloucester?

Accepted Answer

Gloucester is part of the City of Ottawa, so the same rules apply there as anywhere else in the city. Breaking out and removing an old garage floor is a job a concrete contractor can do, and before anyone signs anything, it is worth knowing what the City, the Code and the locate law require. The 2024 Ontario Building Code sets a minimum slab thickness of 75 mm for a floor-on-ground such as a garage floor, and requires a compressive strength of at least 32 MPa for the new concrete.

Question 4

Sunken garage floor in Riverside South: who do I call?

Accepted Answer

A sunken garage floor slab is a concrete job, so start with a concrete contractor who works on garage slabs in the Ottawa area. Before you call anyone, a few things are worth knowing so you can have a useful conversation. Since March 1, 2026 the City of Ottawa has required a hardscaping contractor licence for businesses that install or alter hard landscaping features on private property, such as concrete pads, steps, walkways and patios.

Garage Floors

What concrete strength does Ontario's Code set for a garage floor?

My Stittsville garage floor slopes toward the house: what now?

Who should break out an old garage floor in Gloucester?

Sunken garage floor in Riverside South: who do I call?