Exterior Steel Stairs: Design, Finish and What Drives Cost

Outdoor steel stairs work well in Ontario when three things are right: a tread that sheds snow and water, a finish that keeps the steel from rusting (usually hot-dip galvanizing), and footings and connections that stay put through freeze and thaw. The rise, run and width rules are the same as for an interior stair, but exterior stairs have their own guard, handrail and landing details. This guide covers the design choices, finish options and cost drivers for exterior steel stairs on homes, multi-unit buildings and commercial sites.

Where exterior steel stairs make sense

Steel is a common choice outside because it is strong in thin sections, doesn't rot, and can be prefabricated and installed quickly. Typical uses include:

• Deck and porch stairs for houses, where steel replaces pressure-treated wood stringers
• Secondary suite entrances, such as a side or rear stair down to a basement apartment or up to a second-floor unit
• Exterior exit stairs on small commercial and multi-unit buildings
• Stairs to loading areas, mezzanine doors and equipment platforms
• Stair towers and roof access stairs on industrial buildings, covered in industrial steel stairs and roof access stairs

If you are deciding between steel and poured concrete for an outside stair, see steel stairs vs concrete stairs.

Code points that change outside

Exterior stairs follow Section 9.8. of the 2024 Ontario Building Code for Part 9 buildings, the same section that governs interior stairs. Rise, run, uniformity and width are covered in our guide to Ontario Building Code rules for steel stairs. Larger buildings fall under Part 3, which has its own exit stair rules, and stairs there are designed by the building's architect and engineer. In Part 9, a few rules matter more outdoors:

Guards

A guard is required on each open side where the walking surface is more than 600 mm above the adjacent surface within 1.2 m. Required heights under Article 9.8.8.3.:

On a flight of steps, guard height is measured from a line through the tread nosings. Openings, climbability and loads are covered in OBC guard and handrail rules for steel railings.

Handrails

For stairs serving a single dwelling unit, exterior stairs with not more than 3 risers don't need a handrail, and exterior stairs with more than 3 risers need only one handrail where they serve not more than one dwelling unit or a house with a secondary suite. Other stairs follow Table 9.8.7.1.: outside dwelling units, a straight stair narrower than 1,100 mm needs a handrail on at least one side, while curved stairs and stairs 1,100 mm or wider need handrails on both sides.

Landings

A landing is required at the top and bottom of each flight. At the bottom of an exterior stair it can be omitted if there is no obstruction, such as a gate or door, within the lesser of the stair width or 900 mm (for stairs serving a single dwelling unit) or 1,100 mm (for other stairs). At the top, a landing can be omitted on an exterior flight of not more than three risers serving a secondary entrance to a single dwelling unit, provided the main door slides or swings away from the stair and only a storm or screen door swings over it. That exception doesn't apply where the secondary entrance is also the main entrance to a unit in a house with a secondary suite.

Slip resistance

Treads and landings of stairs other than those within dwelling units or houses with a secondary suite need a slip-resistant finish or slip-resistant strips. Even where it isn't required, a slip-resistant tread is the sensible choice for an outdoor stair in an Ontario winter.

Treads for snow, ice and rain

The tread is the decision that most affects how an outdoor stair performs in winter.

Two practical points: grating treads should have a visible nosing so people can see the edge of each step, and anything that traps water, such as a closed pan or a plate laid flat against a stringer, needs drainage so it doesn't hold ice or rust from inside.

Finishes: galvanizing, paint and powder coat

Exterior steel needs a durable finish. The common options:

• Hot-dip galvanizing. The fabricated stair is dipped in molten zinc, which coats inside and out, including welds and hollow sections. In Canada, galvanizing of fabricated steel is done to CSA G164. It is the standard choice for outdoor stairs because the zinc protects the steel even where the surface is scratched.
• Galvanizing plus paint or powder coat (a duplex system). Adds colour and extends service life. The galvanized surface needs proper preparation before coating, so this is usually arranged with the galvanizer and coater rather than painted on site.
• Paint or powder coat over primed steel. Looks good when new, but once the coating is chipped the steel underneath starts to rust. Better suited to covered locations. Note that Part 9 requires exterior steel columns susceptible to corrosion to have at least one coat of rust-inhibitive paint (Article 9.17.3.3.), which is a minimum, not a recommendation.

Galvanizing affects the design as well as the finish:

• Vent and drain holes are needed in hollow sections, such as HSS stringers, posts and handrails, so zinc can flow in and out and trapped air can escape. They have to be on the shop drawings before fabrication.
• Size limits. Galvanizing kettles have a maximum size, so a long stair may be fabricated in sections and bolted together after galvanizing.
• Bolted field connections are preferred, because field welding burns off the zinc and has to be touched up with a zinc-rich repair coating.

Foundations, connections and drainage

An outdoor stair is only as stable as what holds it up.

• Footings below frost. Posts and landing columns bearing on soil need footings deep enough to avoid frost heave. Part 9 sets minimum foundation depths in Table 9.12.2.2. based on soil type and drainage, and exterior concrete steps with more than two risers have to meet those depths too. Your designer or engineer sets the depth for your site.
• Base plates above grade. Setting posts on base plates anchored to concrete piers that finish above grade keeps the steel out of wet soil and snowmelt. We compare the options in embedding steel posts in concrete vs base plates.
• Attachment to the building. The top of the stair often hangs from a landing, deck or wall. The connection must suit what it fastens to (concrete, masonry, steel or wood framing) and must be designed, not improvised.
• Separating steel from treated wood. Some wood preservatives are corrosive to steel and zinc, so use suitable fasteners and separation where galvanized steel meets treated lumber.
• Let water out. Avoid pockets where water and leaves collect, cap the tops of tubes, and slope landing surfaces so water runs off.

What drives the cost of an exterior steel stair

Exterior stairs are priced job by job, the same as interior stairs. The main drivers:

• Layout: straight run, a stair with an intermediate landing, or a switchback with posts and landing framing
• Total rise and width: more risers mean longer stringers and possibly a mid-landing
• Tread type: grating, plate, pans or a separate tread material
• Guards and handrails: often a large share of the total, especially on a tall stair or with decorative infill
• Finish: galvanizing, and whether it is painted or powder coated after
• Footings and anchorage: new piers, base plates and anchors, and who does the concrete work
• Access and installation: crane or boom truck needs, sections that must be bolted together on site, and working around an occupied building

For a fuller breakdown of how stair quotes are built, read how much steel stairs cost in Ontario.

What to send for an outdoor stair quote

• Total rise from the finished landing or deck to finished grade or paving
• The space available for the run and any landing
• What the stair serves (house, secondary suite, commercial exit, platform)
• Tread type and railing style you have in mind
• Finish preference (galvanized, or galvanized and painted or powder coated)
• What the top attaches to, and what is at the bottom (existing concrete, soil, paving)
• Photos and any drawings

Exterior steel stairs from Procut

We fabricate custom steel stairs and railings in our shop in Erin, with CWB certified welding and shop drawings prepared in house, and deliver across the GTA and Ontario. Engineering services are available for projects that need them. We can prime or galvanize your stair to suit the job, and installation is by your installer or contractor.

Send your measurements or drawings for a free quote, or see our services for our miscellaneous steel fabrication work.