Steel vs. Timber Stringer Staircases Ontario: Structural Comparison & 2026 Costs

The stringer is the structural backbone of a staircase — the beam or frame that carries all tread load from the upper floor to the lower. The two fundamentally different stringer materials are steel and timber. This guide compares them across every relevant dimension: structural performance, visual outcome, cost, OBC compliance, and which to choose for your Ontario home.

What Is a Stringer on a Staircase?

A staircase stringer is the inclined structural member that runs along each side (or centre) of the stair flight, supporting the treads. The stringer transmits the full live load of the staircase — the weight of people, furniture, and dynamic loading — into the floor structure at top and bottom. Without an adequate stringer, a staircase will flex, bounce, or fail structurally.

Types of Stair Stringers

• Mono-stringer (single central beam): One steel beam runs up the centre of the staircase. Treads cantilever to each side. Used for floating/open-riser designs. Requires P.Eng engineering sign-off in Ontario.
• Double steel stringer: Two steel beams, one on each side of the staircase. Treads span between them. Used for open-riser staircases where a wood box stringer wouldn’t be appropriate.
• Wood box stringer (closed stringer): A timber beam routed or notched to accept tread and riser ends. Traditional appearance. Used for closed-riser staircases.
• Open wood stringer (cut stringer): A timber beam with the profile notched to expose the tread nosing and riser face from the side. Decorative — the step profile is visible from beside the stair.
• HSS stringer: A Hollow Structural Section (square or rectangular steel tube) used as a stringer — common in commercial and heavy-residential applications. Stronger than open-profile steel for equivalent weight.

Steel Stringers

Mono-Stringer (Single Central Steel Beam)

The mono-stringer is a single steel beam — typically a 150×75mm or 200×100mm rectangular hollow section (RHS) — that runs up the centreline of the stair flight. Treads are welded or bolted to the top face of the beam, cantilevering equally to each side. The visual result is a “floating” staircase: treads appear to project from a single spine, with open space on both sides.

Mono-stringer staircases in Ontario require P.Eng engineering review because the cantilever load path is complex — the beam must resist both vertical (gravity) and torsional (twisting) forces under live load. C.O.R.S includes P.Eng sign-off on every mono-stringer design at no additional cost.

Double-Stringer (Two Side Steel Beams)

A double steel stringer uses two parallel beams, one on each side of the staircase. Treads are supported at both ends — reducing cantilever stress and allowing a wider range of tread widths. Double stringers are more structurally forgiving than mono-stringers and can accommodate wider staircases or heavier materials. They are the standard structural choice for open-riser staircases that aren’t designed to the floating mono-stringer aesthetic.

HSS Stringer — What It Is and When It’s Used

An HSS stringer uses Hollow Structural Section steel — a closed-section tube (square, rectangular, or circular). HSS stringers provide excellent torsional resistance compared to open steel sections like wide-flange (W-shape) or channel (C-shape) profiles. In staircase applications, this matters because a staircase stringer resists combined bending and twisting loads. HSS is common in architecturally specified residential projects and in commercial applications where high load capacity and clean geometry are both required.

Timber Stringers

Wood Box Stringer (Traditional Closed Stringer)

A wood box stringer is a solid timber beam — typically 2×12 dimensional lumber or engineered LVL — routed and dadoed to accept tread and riser ends. The tread and riser fit into the routed pocket, creating a rigid connection. This is the traditional stair stringer configuration used in residential construction for over a century. Advantages include ease of on-site modification, low cost, and proven code acceptance. Disadvantages include susceptibility to squeaking over time as wood dries and joints loosen, and limited span capability compared to steel.

Open (Cut) Wood Stringer

An open or “cut” stringer has the tread profile notched out of the face of the timber beam, so the tread nosing and riser are visible from the side of the staircase. Decorative — the step geometry is an architectural feature. Open stringers reduce the structural cross-section of the beam and are limited to narrower spans and lighter-duty applications. C.O.R.S typically uses open stringers for decorative side panels on timber staircases where the primary structure is a separate closed stringer or steel beam.

Open vs Closed Stringer — What’s the Difference?

The “open vs closed stringer” terminology refers specifically to whether the stringer face is exposed:

• Closed stringer: The beam runs continuously from bottom to top. Tread and riser ends are hidden inside the stringer — you see only the stringer face, not the tread ends.
• Open stringer (cut stringer): The stringer profile is notched so tread nosings and risers are visible from the side. The step geometry is exposed as a design element.

This is different from the “open riser vs closed riser” choice, which refers to whether there is a vertical board between treads. A staircase can have an open stringer with closed risers, or a closed stringer with open risers, depending on the design intent. See our open riser vs closed riser comparison guide for that decision.

Steel vs. Timber Stringer: Full Comparison

The Workshop Dry-Fit Advantage (C.O.R.S Process)

Every C.O.R.S staircase — steel or timber — is fully assembled in our Barrie-area workshop before installation day. For steel stringer staircases, this means the complete mono or double stringer is fabricated, treads are mounted, and the full assembly is verified for OBC compliance in the shop. On installation day, every bracket fits, every tread is level, and no adjustment is needed on-site. This eliminates the single most common cause of cost overruns on custom staircase projects: on-site fit problems discovered after delivery.

Frequently Asked Questions — Steel and Timber Stringers

What is a mono stringer staircase?

A mono stringer staircase uses a single central steel beam running up the middle of the stair flight, with treads cantilevering outward to each side. The result is a “floating” appearance — treads appear to project from a single spine. Mono-stringer staircases require P.Eng structural engineering in Ontario due to the complex cantilever load path. C.O.R.S includes P.Eng sign-off on all mono-stringer designs. See our floating staircase Ontario guide for full design details.

What is an HSS stringer?

An HSS stringer uses a Hollow Structural Section — a closed steel tube — as the staircase beam. HSS provides superior torsional resistance compared to open steel sections, making it the preferred stringer profile for architecturally specified residential and commercial staircase projects in Ontario. Common HSS sections used for stringers include 150×100×6.4mm and 200×100×6.4mm rectangular tube.

What is the difference between an open stringer and a closed stringer?

A closed stringer runs continuously along the side of the staircase — tread and riser ends are hidden inside the beam. An open (cut) stringer has the step profile notched out, making tread nosings and risers visible from the side. The visual difference is significant: closed stringers give a clean, box-like appearance; open stringers expose the step geometry as a decorative feature. Both can be used with closed or open risers.

How much does a steel stringer staircase cost in Ontario?

A mono-stringer (floating) staircase in Ontario costs $15,000–$21,000 installed in 2026, including P.Eng engineering and building permit. A double steel stringer open-riser staircase costs $11,000–$16,000 installed. A timber box stringer with closed risers costs $8,000–$13,000. All C.O.R.S pricing includes workshop dry-fit, delivery, installation, and permit coordination.

Can I replace a timber stringer with a steel stringer?

Yes — stringer replacement is one of the most common staircase renovation projects C.O.R.S undertakes. Replacing a wood box stringer with steel opens the possibility of removing risers (going from closed to open riser), changing the visual character of an existing staircase completely. The structural opening size typically remains the same; only the stringer profile and tread/riser configuration changes. A building permit is required.

Related C.O.R.S Resources

• Floating staircase Ontario — mono-stringer design, P.Eng, costs
• Open riser vs closed riser stairs Ontario — which stringer type each requires
• Custom staircase cost Ontario 2026 — all stringer types and configurations
• Staircase landing requirements Ontario OBC — how landings connect to stringer design
• Glass railing Ontario — railing options for steel stringer staircases

Get a Steel or Timber Stringer Quote for Your Ontario Staircase

C.O.R.S serves Barrie, Simcoe County, and the Greater Toronto Area with no travel surcharge within Simcoe County. Every stringer staircase project includes P.Eng engineering where required, workshop dry-fit, building permit coordination, and one-day installation for single-flight designs.

Call (705) 623-0371 or request a free quote online to discuss your stringer preference and get a fixed, all-in price for your staircase project.