What base should go under a concrete patio in Kanata?

For a floor-on-ground, Ontario's 2024 Building Code sets not less than 100 mm of coarse clean granular material beneath floors-on-ground generally, though the Code says that layer need not be installed under slabs in garages, carports or accessory buildings. For a patio, we found no Code thickness or base depth requirement; the Code standard for exterior flatwork is 32 MPa concrete, and we found no statement on whether that provision binds a patio built without a permit. The base specification for your patio comes from the contractor's written quote, not from a code section.

The National Research Council's Canadian Building Digest 182 notes that coarse-grained soils such as sands and gravels do not heave, while clays, silts and very fine sands will support the growth of ice lenses. The 2024 Ontario Building Code's appendix adds that clay soils are most prone to expansion and contraction due to moisture. Ask the contractor what soil is under your yard and how that affects the base depth and material they are specifying, and get the answer in writing.

Before anyone digs, a locate request must go through Ontario Dig Authority. Under the Ontario Underground Infrastructure Notification System Act, 2012, an excavator shall not dig until each member has responded, and a standard request is submitted at least five business days before the dig is expected to start. Locates are free. Ask who will submit the request and whether any private lines to a garage, shed or outdoor lights will also be marked.

On the City side, the hardscaping contractor licence has been required since March 1, 2026 for any business installing a concrete patio, walkway or steps on private property. The City requires that licensed contractors carry commercial general liability insurance of not less than $2,000,000 and automobile liability of not less than $2,000,000, provide a written contract, and give you a copy of the City's Landscaping Education Guide. Ask to see the contractor's licence and check the City's published list yourself. For zoning, both By-law 2008-250 and By-law 2026-50 apply to applications deemed complete on or after March 11, 2026, with the most restrictive provisions of both applying; confirm the soft landscaping rules for your lot with the City before you finalise the patio size.

A few things worth asking the contractor to spell out in the quote before you sign: the depth and material of the base, what excavation and removal of existing material is included, whether cold-weather protection is covered if the pour happens when the air temperature is below 5 °C, and whether the minimum charge applies to your job size. Ask the contractor to show you exactly what the line item for base preparation covers.