Deck code in Alberta: loads, footings, guards and stairs

In Alberta, a deck serving one home must be built to carry the roof snow load or 1.9 kPa (about 40 lb/sq ft), whichever is greater, and it needs a guard on any side where the drop is more than 600 mm (2 ft) (NBC(AE) 2023, 9.4.2.3 and 9.8.8.1). That's the second printing of the 2023 Alberta Edition of the building code, in force since 17 August 2026. In Calgary, a covered deck, or an uncovered one more than 0.6 m (2 ft) above grade at any point, also needs a building permit (The City of Calgary, decks).

What changes as a deck gets higher?

Most of the deck rules switch on at a height. Three different heights matter, and they're measured differently: the drop beside the walking surface for guards, the height of the joists for footings, and the height of the deck surface for the permit and the taller guard.

Here is what each threshold triggers for a deck serving one home, as of October 2026:

Note: thresholds for decks serving a single home; decks shared by more units carry heavier loads. These are minimums, and the City of Calgary reviews each deck at permit and inspection.

The guard numbers are explained in full, with the sphere tests, in the guard height guide. On a deck, the main thing to plan for is the 1 800 mm line: a walkout deck off a main floor often lands close to it, and crossing it changes the railing you buy.

How much weight does a deck have to carry?

A deck serving one home must be designed for the specified roof snow load or 1.9 kPa (about 40 lb/sq ft), whichever is greater (NBC(AE) 2023, 9.4.2.3). The code's note says the same rule covers balconies, verandas and flat roofs over garages and carports that people use, and that a platform shared by more than one home takes the higher loads in Part 4 (NBC(AE) 2023, Note A-9.4.2.3.(1)).

In practice the load shows up in the joist and beam sizes. Calgary's checklist sends you to the Canadian Wood Council's prescriptive deck span guide, and beams or joists outside its span tables need an engineer (The City of Calgary, deck checklist 2026). The City's own worksheet, for a simple single-level rectangular deck, assumes SPF No. 1 and No. 2 lumber and caps joist and beam cantilevers at 2 ft (The City of Calgary, deck worksheet 2026).

How deep do deck footings need to be in Calgary?

At least 1.2 m (4 ft) below ground under Calgary's checklist, unless an engineer designs or reviews a shallower foundation. The checklist gives frost heave as the reason (The City of Calgary, deck checklist 2026).

The code itself sets footing depth by soil. In clay, or in soil that isn't clearly defined, a foundation with no heated space goes 1.2 m down, and no less than the frost depth (NBC(AE) 2023, Table 9.12.2.2). It then waives that depth for a small, low deck of one storey and no more than 55 m² (592 sq ft), with joists no more than 600 mm (2 ft) above the ground and no roof. The deck also has to stand free of the house, unless you can show its movement won't harm the structure it's fixed to (NBC(AE) 2023, 9.12.2.2.(7)). A registered professional can also design for less depth (NBC(AE) 2023, 9.12.2.2.(5)).

A deck on surface footings has one more rule. Unless the soil is rock or well-drained coarse soil, you need a way to re-level it: a crawl passage under the deck at least 600 mm (2 ft) high and 600 mm wide, or decking that lifts off easily (NBC(AE) 2023, 9.12.2.2.(8)).

Calgary's checklist adds these items on top of the code, as of August 2026:

Note: these come from the City's uncovered deck checklist and worksheet (The City of Calgary, deck checklist 2026). The worksheet itself says its tables may exceed code minimums.

Low decks still have to be held down. Posts under a deck whose joists are no more than 600 mm above ground must be anchored to the foundation, or the joists anchored to the ground, against uplift, unless the deck meets the same small, freestanding, roofless conditions as the footing waiver (NBC(AE) 2023, 9.23.6.2).

What are the rules for deck stairs?

Deck stairs serving one home are private stairs, so each step can rise 125 mm to 200 mm (4.9 in to 7.9 in) on a run of 255 mm to 355 mm (10 in to 1 ft 2 in) (NBC(AE) 2023, Tables 9.8.4.1 and 9.8.4.2). They must be at least 860 mm (2 ft 10 in) wide (NBC(AE) 2023, 9.8.2.1). A stair that runs under an upper deck needs the house headroom of 1 950 mm (6 ft 5 in) (NBC(AE) 2023, 9.8.2.2).

Short deck stairs get several breaks that inside stairs don't:

• Handrails. None needed at 3 risers or fewer; above that, one handrail is enough for a stair serving one home (NBC(AE) 2023, 9.8.7.1).
• Top landing. It can be left out at a secondary entrance with no more than 3 risers, if the main door slides or swings away from the stair and only a storm or screen door, with hold-open hardware, swings over it.
• Bottom landing. It can be left out if no gate or door sits within 900 mm (2 ft 11 in) of the stair, or within the stair's width if that's less (NBC(AE) 2023, 9.8.6.2).
• Sloping ground. Where the bottom step meets a sloping patio or driveway, that riser's height can vary across the stair by no more than 1 in 12 (NBC(AE) 2023, 9.8.4.4).
• The step at the door. Where ice or snow could block a door, it may open onto a single step with a riser of no more than 150 mm (5.9 in) (NBC(AE) 2023, 9.9.6.6).

This is the steepest three-riser stair a home's deck can have, at a 200 mm rise and 255 mm run, with the 1 950 mm headroom line:

Three risers at 200 mm lift you 600 mm, which is right at the guard trigger. The stair guide covers inside stairs, and Calgary needs a permit to add stairs to an existing deck that's more than 0.6 m (2 ft) above grade.

What else does Calgary check on a deck?

Where the deck sits, and what it turns into. A deck at the front of the house, closer than 1.2 m (3 ft 11 in) to a side property line, closer than 6 m (19 ft 8 in) to the rear one, or in or within 6 m of a floodway needs a development permit as well as the building permit (The City of Calgary, decks). Electrical or plumbing on the deck needs a trade permit.

Add a roof attached to the house and the City treats the deck as an addition; a platform attached above the main floor is a balcony, also an addition. The home addition cost guide covers what that means, and the Calgary building permit guide lists the fees and timelines.

A deck over a basement bedroom window needs care too. Calgary's egress advisory allows an egress window under a deck only with at least 760 mm (2 ft 6 in) between grade and the deck's underside, and with the window opening right at the deck's edge (The City of Calgary, egress advisory 2022). The egress window guide has the window rules.

What does a walkthrough show for a deck?

A deck drawn on the plan shows up on the LED floor at full size, next to the kitchen or family room it opens from. You can walk from the patio door to the top of the stair, see where the bottom landing falls, and check whether a gate lands inside that 900 mm. The elevation goes up on the wall-size screen, where you can compare the deck height with the window sills beside it.

Changes are made on the spot, and you keep the recording of the session. Sessions are quoted for your plan and nothing is paid at booking (see pricing). Browse the other building code guides, read how sessions work for homeowners, or book a session.