What is the maximum deck height allowed without a railing in Ottawa?

Under the Ontario Building Code, which governs all residential construction in Ottawa, a deck requires a guard (the code term for what most people call a railing) when the walking surface is more than 600mm (approximately 24 inches) above the adjacent finished grade. This means any deck surface that sits higher than about two feet off the ground at any point along its perimeter must have a compliant guard installed.

This 600mm threshold is measured vertically from the deck surface to the ground directly below, and it applies at every point around the deck's perimeter, not just the average height. This is a detail that catches some Ottawa homeowners off guard because many properties in this region have grading that slopes across the yard. Your deck might be only 400mm above grade on one side but 700mm on the downhill side. In that scenario, you need a guard along any section where the drop exceeds 600mm, even if other portions of the deck are low enough to be exempt.

When a guard is required, the Ontario Building Code specifies a minimum height of 900mm (approximately 36 inches) measured from the deck surface. However, there's an important exception that applies to many Ottawa homes: if the height of the deck above grade exceeds 1,800mm (roughly 6 feet), the minimum guard height increases to 1,070mm (42 inches). This commonly applies to second-storey decks or walkout basements on sloped lots, which are fairly common in neighbourhoods like Barrhaven, Kanata, and parts of the Glebe where terrain changes are significant.

The guard itself must meet specific structural requirements. It needs to resist a horizontal load of at least 0.75 kN per metre applied at the top, and the design must prevent the passage of a 100mm sphere at any point. This sphere test is what effectively limits the maximum spacing between balusters or any openings in the guard design. Horizontal cable or wire railing systems must also meet this requirement at every point between cables, which can mean tighter spacing than some homeowners expect.

For Ottawa specifically, the guard requirements have practical construction implications tied to our climate. Guards must be securely fastened to the deck structure in a way that accounts for the stress from snow loads and ice buildup. A guard that meets code in summer can fail under the added weight of accumulated snow and ice that's common through Ottawa's December-to-March period. Through-bolting guard posts to the rim joist or using code-compliant post-mount hardware is standard practice here, as opposed to simply lag-screwing posts, which can loosen over time as freeze-thaw cycles work on the connections.

If your deck project falls below the 600mm threshold and you're considering skipping the guard entirely, it's still worth thinking about whether a railing makes practical sense for your situation. Ottawa's winters bring icy conditions from November through March, and even a low deck surface can become hazardous when covered in a thin layer of ice. Many Ottawa homeowners with ground-level decks opt for at least a partial railing near entry points as a safety measure, even when code doesn't mandate it.

Getting the details right on guard height, post attachment, and baluster spacing before construction starts avoids failed inspections and costly retrofits. The Ottawa Patios knowledge hub can connect you with professionals who understand both the code requirements and the practical realities of building in this climate.

---

Looking for experienced contractors? The Ottawa Construction Network connects Ottawa homeowners with qualified professionals:

• Homeupgraders
• RenoMotion Inc.
• ALTIOR CONSTRUCTION
• Marcduboisservices
• Prime Property Works