Ontario Building Code Rules for Steel Stairs

The Ontario Building Code doesn't have a separate rulebook for steel stairs: a steel stair must meet the same Part 9 rules for rise, run, width, headroom, landings, handrails and guards as any other stair. Under the 2024 Ontario Building Code, private stairs may have a rise of up to 200 mm and a run of at least 255 mm, while public stairs are limited to a 180 mm rise with at least a 280 mm run. Most residential stairs must be at least 860 mm or 900 mm wide, depending on what they serve. The details below come from Section 9.8. of the 2024 Ontario Building Code.

Which stair rules apply

Part 9 of the Ontario Building Code covers buildings of three storeys or less with a building area up to 600 m² in the residential, business, mercantile and medium- and low-hazard industrial groups. That includes houses, most townhouses and small commercial buildings. Larger buildings fall under Part 3, which has its own stair requirements, and stairs there are designed by the building's architect and engineer.

Within Part 9, the rules depend on the type of stair:

• Private stairs: interior stairs within a single dwelling unit or a house with a secondary suite, exterior stairs serving one, and exterior stairs serving a garage that serves one.
• Public stairs: all stairs that are not private or service stairs, such as those in multi-unit common areas and commercial buildings.
• Service stairs: stairs serving only service rooms or service spaces.
• Other categories: stairs to unoccupied attic space, stairs to crawl spaces, and stairs serving small mezzanines in live/work units.

Riser height and tread run

Source: 2024 Ontario Building Code, Division B, Table 9.8.4.1. Imperial values are rounded.

A few definitions make the table easier to use:

• Rise is measured as the vertical nosing-to-nosing distance between treads.
• Run is the horizontal distance between adjacent tread nosings.
• Tread depth is the full front-to-back depth of the tread. It must be at least the run and no more than the run plus 25 mm, which limits how far a nosing can overhang the tread below.

Uniformity tolerances

Steel stairs are fabricated in a shop, which makes uniform steps easier to achieve, but the finished stair still has to meet the tolerances once it is installed and the floor finishes are in:

• Risers in a flight must be uniform within 5 mm between adjacent treads or landings, and within 10 mm between the tallest and shortest riser in the flight.
• Rectangular treads must have a uniform run within 5 mm between adjacent treads and 10 mm between the deepest and shallowest in the flight.
• Treads may not slope more than 1 in 50.

The usual way to fail these on a steel stair is at the top and bottom risers, where the finished floor ends up thicker or thinner than assumed. Tell your fabricator the finished floor build-up at both ends before the stair is detailed.

Nosings

The top of each tread nosing needs a rounded or bevelled edge extending between 6 mm and 14 mm horizontally from the front of the nosing (as little as 3 mm where a resilient nosing cover is used). On steel treads, that means breaking the sharp edge of checker plate or grating nosings rather than leaving a square cut edge.

Open risers

Open risers (no riser plate between treads, common on steel and floating stairs) are permitted on interior and exterior stairs serving a single dwelling unit or a house with a secondary suite, fire escapes, maintenance stairs, stairs serving service rooms and stairs in most industrial occupancies. They are not permitted on other stairs.

Stair width and headroom

Clear height is measured vertically, over the full clear width of the stair, from a line tangent to the tread and landing nosings to the lowest point above. Stringers, handrails and brackets may not project more than 100 mm into the required width, which matters for steel stairs with wide channel stringers inside the walls.

Flights, landings, winders and spirals

• Maximum flight height: a single flight may not rise more than 3.7 m (about 12 ft 2 in) vertically without a landing.
• Minimum risers: interior flights need at least three risers, except within a dwelling unit.
• Landings are required at the top and bottom of each flight and where a doorway opens onto a stair, with exceptions for doors at the top of a stair within a dwelling unit that swing away from the stair, and for some short exterior stairs. Landings must be at least as wide and as long as the stair, though a landing that turns less than 90° doesn't need to be longer than the lesser of the stair width or 1,100 mm. Where a door swings toward a stair, its full swing must be over the landing.
• Winders are allowed within dwelling units, turning through no more than 90° with each tread turning between 30° and 45°.
• Spiral stairs need handrails on both sides (the outer one at least 1,070 mm high), at least 660 mm clear width between handrails, risers no more than 240 mm, treads at least 190 mm deep measured 300 mm from the narrow-side handrail, and at least 1,980 mm of headroom. A spiral stair can serve as the only means of egress only where it serves no more than 3 people.

Loads and construction

Stairs must be designed for uniform specified loads of 1.9 kPa (about 40 psf) where they serve one dwelling unit or a house with a secondary suite, and 4.8 kPa (about 100 psf) for other stairs. The code gives prescriptive sizes for wood stringers, but not for steel ones, so steel stringers, treads and connections are sized by design, usually on the fabricator's shop drawings and, for public and commercial stairs, by an engineer.

Common steel stair construction includes:

• Stringers of steel channel, plate or HSS, sized for the span and load.
• Treads of checker plate, steel grating, or steel pans filled with concrete, or wood or stone treads set on steel brackets.
• Connections welded in the shop where possible and bolted on site, so the stair goes in quickly.
• Finish to suit the location: primer for interior stairs to be painted, galvanizing for exterior stairs.

Treads, landings and ramps need a wear-resistant, slip-resistant finish that is smooth, even and free of open defects. Outside dwelling units, treads and landings need a slip-resistant finish or slip-resistant strips, and the leading edges of treads and landings must be marked with a colour contrast or distinctive pattern. Most stairs outside dwelling units also need tactile attention indicators at the top. These are easier to plan into a steel stair at the detailing stage than to add later.

Handrails and guards on steel stairs

Every stair needs handrails, and most need guards on open sides, with their own height, opening, climbability and load rules. We cover those in detail in Ontario Building Code guard and handrail rules for steel railings. Plan the stair and railing together so the posts, stringers and handrail brackets work as one design.

Planning a code-compliant steel stair

1. Measure the total rise from finished floor to finished floor, including flooring, and the space available for the run.
2. Pick the stair type (private, public or service) so you know which limits apply.
3. Lay out risers and treads within the limits, and check headroom at every point along the stair.
4. Check width and landings, including door swings at the top and bottom.
5. Have the stair detailed and, where needed, engineered, with stringer sizes, connections and anchorage.
6. Review shop drawings before fabrication. Changes are cheap on paper and expensive in steel.

Welding quality matters on stairs because the connections carry people. See why hire a CWB-certified fabricator, and for budgeting, what drives steel stair cost in Ontario.

Custom steel stairs from Procut

We fabricate custom steel stairs and railings in our shop in Erin, with shop drawings prepared in-house and CWB certified welding, and deliver across the GTA and Ontario. Send your floor-to-floor height, opening size and drawings, and we will prepare a quote. Engineering services are available for projects that need them.

Request a steel stair quote, or see our services for miscellaneous steel fabrication and delivery.