An accessible parking stall fails inspection for one of three reasons, and only one of them is about the drawing. It is either the wrong count, the wrong geometry, or — most often on the jobs we get called into — a slope the crew never measured because nobody told them the tolerance was two per cent.
After 38 years pouring commercial flatwork in Calgary, we have learned that the accessible stalls are the part of a parking lot most likely to be redone at somebody’s cost. They are also the easiest part to get right, because every number is published. Here is what those numbers are, where they come from, and which ones actually land on the concrete crew.
How many accessible stalls does a Calgary parking lot need?
The count comes from a table in the Alberta Building Code, reproduced as Table 3.8.2.5 in The City of Calgary’s Accessibility Design Guide 2024 and as Table 3.8.2.2 in the Province’s Barrier-Free Design Guide. It scales with the total number of stalls required on the site:
| Parking stalls required | Accessible stalls required |
|---|---|
| 2 – 10 | 1 |
| 11 – 25 | 2 |
| 26 – 50 | 3 |
| 51 – 100 | 4 |
| Each additional 100 | 1 more |
Two things trip people up here. The table keys off the number of stalls required for the use, not the number the owner decided to build. And for adaptable or barrier-free dwelling units, the Barrier-Free Design Guide sets a separate rule at Article 3.8.2.2(5): one accessible stall per unit, regardless of what the table says.
The general stall dimensions, the number of stalls a given use has to supply, and the requirement that stalls be hard-surfaced and sit wholly on the parcel all live in Land Use Bylaw 1P2007, Part 3 Division 6. The Building Code sets the barrier-free minimums on top of that. Where the two disagree, the larger dimension governs — that is the rule to hand your layout crew.
Stall and aisle dimensions
An accessible stall is not just a wider stall. It is a stall plus a marked access aisle that nobody parks in, and the aisle is what makes the stall usable.
| Element | Requirement | Source |
|---|---|---|
| Stall width | 2.4 m minimum | Barrier-Free Design Guide, Art. 3.8.2.2(4) |
| Access aisle | 2.4 m wide, demarcated, no parking | Barrier-Free Design Guide, Art. 3.8.2.2(4) |
| Surface | Firm, slip-resistant, level, paved — stall and aisle both | Barrier-Free Design Guide; City Access Design Standards, Standard 2 |
| Sign height | 1 600 – 2 500 mm above finished surface | Barrier-Free Design Guide, Art. 3.8.2.2(4) |
| Overhead clearance | 3 000 mm recommended minimum | Barrier-Free Design Guide, Art. 3.8.2.2(4) |
| Distance to entrance | Within 50 m of a barrier-free entrance | City Access Design Standards, Standard 1 |
A stall and its aisle together need 4.8 m of formed, hard-surfaced width at minimum. Two stalls sharing one aisle is the usual layout and it is the one to check on the drawing before you form, because a shared aisle that lands on a column, a catch basin or a landscape island is the single most common redesign we see after the base is already compacted.
The City’s Access Design Standards add two placement rules that are easy to miss and expensive to fix in concrete: bumpers and other obstructions must not encroach on the barrier-free path of travel (Standard 4), and the layout must not force someone to travel behind parked vehicles to reach the building (Standard 5). Both of those are decided when the curb line is set, not when the stripes are painted.
The slopes — the part that lands on the concrete crew
This is where the money is. The dimensions are somebody else’s problem until the day of the pour; the slopes are yours.
Cross slope on any barrier-free surface: 1:50 maximum. That is two per cent. It applies to the stall, the access aisle, the path of travel and the ramp surface (City Access Design Standards, Standard 47; Accessibility Design Guide 2024, Section 3.8.3.2). Two per cent is 20 mm of fall in a metre. It is also, not coincidentally, about the drainage you need in a Calgary lot, so the tolerance is not a fight with the grade — it is a fight with sloppy screeding.
Running slope on a ramp: 1:12 maximum under the Building Code (Barrier-Free Design Guide, Art. 3.8.3.4(1)). The City sets a tighter target for development it reviews — 1:20 to 1:25, with a ramp of 3 m or less permitted at 1:12, and 1:16 allowed where a shallower grade is technically infeasible (Access Design Standards, Standard 45). Anything shallower than 1:25 is a sloping walk and does not need to be built as a ramp at all — no handrails, no landings.
Curb ramps are their own geometry. The Accessibility Design Guide 2024 cites CSA B651 for a running slope between 1:15 and 1:10, a cross slope no steeper than 1:50 at intersections, and a level 1 500 × 1 500 mm turning space maintained on the sidewalk behind the ramp (Standard 37). Curb ramps on City right-of-way are built to the current Roads Construction Standard Specifications, which put that concrete in exposure class C-2 — air-entrained, and specified for the freeze-thaw and de-icing salt service it is going to see.
Landings and widths. Ramps need a level landing every 9 000 mm and a 1 500 × 1 500 mm landing at any 90-degree turn. Path-of-travel width is where three documents give three answers: the Building Code minimum is 1 100 mm, the Accessibility Design Guide 2024 calls for not less than 1 600 mm at Article 3.8.3.3, and the City’s Access Design Standards require a minimum of 1 500 mm for exterior paths (Standard 18). Build to the widest figure that applies to your approval path. On a fixed site that decision has to be made before the forms go in, because 100 mm of extra walkway is a curb line, not a trim cut.
Tactile walking surface indicators
TWSIs are the truncated-dome plates at the edge of a drop-off, and they are dimensioned tightly because they are read by a cane and a foot, not an eye.
- Dome height 4 – 5 mm; top diameter 12 – 25 mm; base diameter 10 ± 1 mm greater than the top; 42 – 70 mm centre-to-centre spacing (Accessibility Design Guide 2024, Table 5)
- Band 600 mm wide, set 250 mm back from a stair nosing (City Access Design Standards, Figure D.104)
- At a curb ramp, the indicator band sits 300 – 350 mm from the curb and is 600 – 650 mm deep (Accessibility Design Guide 2024)
- Minimum 50 per cent luminance contrast with the surface around it
- Required at stairs, at unprotected drop edges over 250 mm, at reflecting pools, and where a path enters a vehicular route (Standard 104)
Cast-in plates have to be set in the wet concrete at the right setback, at the right elevation, and dead flat. Surface-applied plates go down after curing and depend on a clean, sound, properly cured slab — which is one more reason the curing on exterior flatwork matters more than it looks like it does.
Details that decide whether it passes
A few requirements sit outside the dimension tables but get checked anyway:
- Slip resistance. All floor surfaces must be slip-resistant, non-glossy and stable, with a coefficient of friction no less than 0.5 (Access Design Standards, Standard 90). A hard steel-trowel finish on an exterior barrier-free path is the wrong finish.
- Gratings and joints. No opening may pass a sphere larger than 13 mm. That rules out wide gaps, and it is worth thinking about when you lay out joints in the flatwork — a control joint that opens over a winter can approach that limit on a route that has to stay smooth.
- Drainage. Curb ramps must be graded so water and snow do not pond, and catch basins are not to be placed directly in front of a ramp (Standards 39 and 40). In a city with as many freeze-thaw cycles as ours, a puddle at the bottom of a ramp becomes an ice sheet at the one place a person cannot avoid.
- Winter. Exterior ramps and stairs have to be kept clear of snow and ice — by maintenance, or by heating and drainage designed in from the start. That is a decision made at the base and conduit stage, not after the first storm.
- Signage. The international symbol of access is painted on the pavement of every off-street barrier-free stall in non-slip paint, plus a vertically mounted sign (Standard 16).
What we check before the pour
On our commercial jobs the accessible stalls get a separate walk-through before any concrete is ordered. It is a short list: confirm the stall count against the required stall count, confirm the aisle is not shared with a hazard, string the cross slope across the stall and the aisle, confirm the path of travel width against the strictest document in play, set the TWSI setback, and confirm the curb ramp landing exists on the sidewalk side. Every one of those is cheap to fix on a string line and expensive to fix with a saw.
If you are pricing a lot, a pad or a walkway system and want the barrier-free portion checked before it is formed, that is part of what our commercial concrete team does on a pre-pour review. We also build the connecting walkways and sidewalks that carry the route from the stall to the door, and the entrance steps and landings at the other end of it. Over 52,000+ projects, the pattern has not changed: the jobs that go smoothly are the ones where somebody checked the slopes before the truck showed up.
FAQ
How many accessible parking stalls are required in Calgary? It follows the Alberta Building Code table: one stall for a lot requiring 2–10 stalls, two for 11–25, three for 26–50, four for 51–100, and one more for each additional 100 required stalls. Barrier-free and adaptable dwelling units get one accessible stall each.
How wide is an accessible parking stall in Alberta? The Barrier-Free Design Guide sets a minimum stall width of 2.4 m plus a 2.4 m marked access aisle — 4.8 m of paved width in total. Where Land Use Bylaw 1P2007 requires a wider general stall, the larger dimension governs.
What is the maximum slope for an accessible parking stall? Cross slope on a barrier-free surface may not exceed 1:50, or two per cent. The same limit applies to the access aisle and the path of travel.
What slope can a curb ramp be? CSA B651, as cited in the City’s Accessibility Design Guide 2024, sets a curb ramp running slope between 1:15 and 1:10, with a cross slope no steeper than 1:50 at intersections and a level 1 500 × 1 500 mm space behind the ramp.
Do access aisles have to be paved? Yes. Both the stall and the adjacent access aisle must be hard-surfaced, firm, slip-resistant and level. A gravel aisle beside a paved stall does not meet the requirement.
Who is responsible if the slope is out of tolerance after the pour? Practically, the contractor who placed it. There is no tolerance stack to hide in at two per cent, which is why the slope should be strung, checked and signed off before the concrete is ordered.
Sources
- City of Calgary, Access Design Standards (Mobility, Vision, Cognitive, Hearing) — https://www.calgary.ca/content/dam/www/pda/pd/documents/development/access-design-standards.pdf
- City of Calgary, Accessibility Design Guide 2024 — https://www.calgary.ca/content/dam/www/pda/pd/documents/licence/ma-accessibility-design-guide-2024.pdf
- Alberta Municipal Affairs / Safety Codes Council, Barrier-Free Design Guide, Fifth Edition — https://ebs.safetycodes.ab.ca/documents/webdocs/PI/Barrier-Free-Design-Guide_WEB-Aug2019.pdf
- City of Calgary, Land Use Bylaw 1P2007, Part 3 Division 6 — Requirements for Motor Vehicle Parking Stalls — https://www.calgary.ca/planning/land-use/online-land-use-bylaw.html?part=3&div=6