Window fall protection in Alberta: sill heights and limiters

In Alberta, an openable window in a home needs a guard or a limiter that holds the opening to 100 mm (3.9 in), unless the bottom of the part that opens is more than 900 mm (2 ft 11 in) above the floor, or less than 1 800 mm (5 ft 11 in) above the ground outside (NBC(AE) 2023, 9.8.8.1). The rule exists to stop small children falling from open windows. It's in the second printing of the National Building Code, 2023 Alberta Edition, in force since 17 August 2026 (Government of Alberta, 2026).

When does a window need fall protection in Alberta?

Any openable window in a residential building needs it, unless one of two exemptions applies. The rule isn't limited to bedrooms or to upper floors. The exemptions do most of the sorting (NBC(AE) 2023, 9.8.8.1.(4) and (5)):

• A high sill. The bottom edge of the openable part sits more than 900 mm (2 ft 11 in) above the finished floor.
• A short drop. That same edge sits less than 1 800 mm (5 ft 11 in) above the floor or ground on the other side.

The code's note explains the target. It is meant for small children, and in practice it reaches windows on the second floor or higher (NBC(AE) 2023, Note A-9.8.8.1.(4)). Notes are guidance; the Sentence is the rule. The note also links the two numbers: the 900 mm sill matches the 900 mm guard height inside a home.

Here's how the exemptions sort typical windows in a house, as of October 2026:

Note: measured to the bottom of the part that opens, not the frame. The City of Calgary decides how the rule applies to a particular window at plan review.

A fixed pane isn't covered by the window rule, since it doesn't open. Large fixed glass beside a stair is covered by a different rule, explained further down.

What counts as a window opening limiter?

A device that holds the window to an opening of 100 mm (3.9 in) or less, measured either way, and that can only be released with tools or special knowledge (NBC(AE) 2023, 9.8.8.1.(4)). The note calls 100 mm the largest opening that protects small children.

The note is specific about hardware. It lists a fixed-stop lever, a fixed-length cable and a fixed-position stop block as devices that can work. Rotary operators, the cranks used on casement and awning windows, can't do it, "even when the crank handle is removed" (NBC(AE) 2023, Note A-9.8.8.1.(4)). It warns that awning windows with scissor hardware may swing open once unlatched, that hopper windows matter only if they open at the bottom as well, and that sliders are the type the rule affects most. For technical detail, it points to ASTM F2090 on window opening control devices.

This drawing compares the same 920 mm tall opening held to the 100 mm limit and opened to the 380 mm width an escape window needs:

The 380 mm by 920 mm opening is the code's own example of the smallest tall escape window, at 0.35 m² (3.8 sq ft) (NBC(AE) 2023, Note A-9.9.10.1.(2)). Held to 100 mm, the same window opens to about 0.09 m².

What if the window is also the bedroom's escape window?

Then the two rules pull against each other, and a high sill is the simplest way out. Every bedroom without sprinklers needs a window or outside door that opens "without the use of keys, tools or special knowledge" to at least 0.35 m², with no side under 380 mm (NBC(AE) 2023, 9.9.10.1). A limiter, by definition, needs tools or special knowledge to release. The code text doesn't say how to reconcile the two on one window.

Calgary's egress advisory reads special knowledge as anything more than one simple motion to release the lock and one simple motion to open the window (The City of Calgary, egress advisory 2022). If you want a limiter on a bedroom's escape window, ask the City before you order the windows.

Raising the sill avoids the conflict. Above 900 mm (2 ft 11 in), the fall rule no longer applies, and the code's note on escape windows suggests sills no higher than 1.5 m (1 500 mm, or 4 ft 11 in) so people can reach them (NBC(AE) 2023, Note A-9.9.10.1.(1)). That's guidance; the code sets no maximum sill height.

Here's how the sill height plays out on an upper-floor bedroom window with a drop of 1 800 mm or more outside, as of October 2026:

Note: the 1.5 m figure is guidance from Note A-9.9.10.1.(1), not a requirement. Window sizes for escape are on the egress window guide.

The drawing shows those two heights on a bedroom wall, with a ceiling at 2 100 mm (6 ft 11 in), the minimum height the code sets over part of every bedroom (NBC(AE) 2023, Table 9.5.3.1).

Does a Juliet balcony need a guard in Alberta?

Yes: a door in a home that opens onto a drop of more than 600 mm (2 ft) needs a guard, or a mechanism that limits the door to an opening of 100 mm (3.9 in) (NBC(AE) 2023, 9.8.8.1.(3)). That covers a French door on an upper floor with no balcony behind it, and a patio door left waiting for a deck that hasn't been built.

The 600 mm trigger is the same one that applies to floors and decks. The guard height guide covers guard heights, baluster spacing and loads.

What about glass beside stairs and doors?

Glass near a stair has its own rule. Inside a home, glazing over stairs, ramps and landings that comes lower than 900 mm (2 ft 11 in) above the treads or landing needs a guard, or must be fixed shut and designed for the lateral loads on balcony guards. Outside homes, the trigger is 1 070 mm (3 ft 6 in) (NBC(AE) 2023, 9.8.8.1.(6) and (7)). In residential buildings, glass in public areas above the second storey that comes within 1 m (3 ft 3 in) of the floor gets the same treatment.

So a big window on a stair landing should start at least 900 mm above the landing, or be planned as a fixed, guard-rated panel. The stair guide shows the landing sizes.

Glass in and beside doors must be safety glass in a few cases. That covers glass in sliding and storm doors, and sidelights over 500 mm (1 ft 8 in) wide that could be mistaken for doors, within or at the entrance to a home. It also covers glass in entrance doors over 0.5 m² (5.4 sq ft) that reaches within 900 mm of the bottom of the door (NBC(AE) 2023, 9.6.1.4). Safety glass here means tempered or laminated glass, or wired glass. How much window a side wall can have near the property line is a separate rule, covered in the windows near the property line guide.

What does a walkthrough show about windows?

Windows show on the LED floor where they sit in each wall, and the elevations go up on the wall-size screen behind the floor, so you see the sill heights beside the room they serve. Standing in a bedroom at full size, you can check where the bed and a desk sit against a window, and whether a landing window lines up with the stair. Changes are made on the spot.

You keep the recording of every session. Sessions are quoted for your plan, with nothing to pay at booking (how quotes work). See the other building code guides and the bedroom size guide, or book a session.