Guard height on a deck 10 m up in Ontario?

At 10 metres up, the 2024 Ontario Building Code requires a guard on any open side where the drop exceeds 600 mm within 1.2 m of the edge. For the deck itself the guard is not less than 1 070 mm high, and Ontario adds a separate rule for exterior stairs and landings more than 10 m above adjacent ground: their guards must be not less than 1 500 mm.

The standard exterior guard height for a deck serving not more than one dwelling unit is 900 mm where the walking surface is not more than 1 800 mm above finished ground, and 1 070 mm in all other cases. At 10 m the deck is well past 1 800 mm, so the 1 070 mm figure applies to the deck's guards.

On infill, the Ontario version of the 2024 Building Code replaces the national rule with a stricter one: every required guard must be designed so that no member, attachment or opening between 140 mm and 900 mm above the walking surface will facilitate climbing. Horizontal rails and cable runs between those heights can facilitate climbing, which is what that rule targets. Confirm any infill design with the City's Building Code Services before committing to it.

For loads, the Code sets a top load of 0.5 kN per metre or a concentrated load of 1.0 kN at any point, and 1.5 kN per metre vertically, for exterior guards serving not more than two dwelling units. Ontario deems guards built to MMAH Supplementary Standard SB-7 to meet the load requirement. A glass, aluminum or other manufactured guard system outside the Code's prescriptive rules requires the manufacturer's information and attachment details with the permit application.

A deck with a walking surface more than 600 mm above adjacent grade and attached to or adjacent to the house requires a building permit from the City of Ottawa. At 10 m that is not in question. The permit drawings must include elevations showing guard and handrail information, and the framing plan must show the deck-to-house connection. The City requires three inspections: Excavation or Foundations before backfill, Framing at completion of structural framing and guards, and a Final inspection. The homeowner or builder books each one 48 hours in advance.

Given the height, work through the guard posts and their connections with a designer or engineer before the permit drawings are finalised.

Because this deck is well above grade and attached to a building, getting the permit application in front of the City's Building Code Services is the immediate next step.