Single Undermount Stringers

A single undermount stringer runs beneath the centerline of the stair treads rather than along the side, hiding the structural support entirely from view. Instead of a visible stringer defining the staircase’s look, the treads appear to float, supported by a single steel spine underneath rather than one on each side. This construction method is one of the most requested options for open-concept homes and commercial spaces where a light, contemporary feel is the priority. Metal and Wood Products fabricates single undermount stringers in two distinct styles, each suited to different spans, budgets, and design goals.

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Design Features

Because a single undermount stringer supports the full width of each tread from below, the stringer itself must be engineered to resist twisting under load rather than simply bending — a different structural challenge than a two-stringer system, where the load is shared across two support points. Getting this right takes precise fabrication and profile selection. Metal and Wood Products builds single undermount stringers using two proven approaches.

tube side stringer

Tube Style

These single undermount stringers use standard H.S.S. (hollow structural section) tubing as the main stringer. Tube construction offers predictable strength, efficient material use, and a clean, uniform profile — a practical, cost-effective choice for standard spans and straightforward stair runs.

Fabricated Tube Single Undermount

Fabricated Tube Style

These single undermount stringers are fabricated from plate steel to create a crisp, sharp-edged profile in custom sizes and shapes. Because the stringer is built rather than cut from standard tubing, fabricated tube stringers allow for tighter tolerances and unique geometries — well suited to projects with non-standard dimensions or specific architectural requirements.

Structural Performance

Single undermount stringers carry different structural demands than side-mounted or double-stringer systems. Since one stringer supports the entire tread width from underneath, torsional stiffness is the key engineering consideration — the stringer profile and wall thickness must be sized to prevent twisting, particularly on wider treads or longer spans between supports.

All single undermount staircases are engineered to meet BC Building Code requirements for private stairs under Section 9.8, including load capacity, guardrail integration, and tread dimensions. Because the support structure is hidden beneath the treads, connection detailing between the stringer, treads, and building framing is critical — proper fabrication here is what keeps a floating staircase rigid and quiet over years of use, not just on install day.

Customization Options

Each single undermount staircase is custom-fabricated to the project’s exact dimensions, tread widths, and design intent. Stringer profile and wall thickness are calculated based on span, tread depth, expected load, and material selection.

Finishes include powder coating in a wide range of colors, painted finishes to match interior palettes, or a raw or clear-coated steel for a more industrial look. Tread materials range from solid hardwood and engineered wood to steel, concrete, or glass. Because the stringer disappears beneath the tread, railing systems can be mounted with minimal visual interruption — a common pairing for glass or cable rail systems where an unobstructed sightline is the goal.

Ideal Applications

Single undermount stringers are especially well suited to open-concept residential interiors, feature staircases, and any space where an airy, floating appearance is the design priority. Because the support structure is fully concealed, light passes beneath and around each tread — a detail that reads especially well near large windows or in spaces with sightlines between floors.

Commercial applications include lobbies, showrooms, and hospitality spaces where a staircase needs to feel like a design statement rather than a structural necessity. For residential projects, single undermount stringers pair naturally with glass or cable railings, engineered hardwood treads, and other detailing common to modern and transitional interiors.

Frequently Asked Questions

ABOUT OUR SINGLE UNDERMOUNT STRINGERS

Single undermount staircase costs depend on stringer style (tube or fabricated plate), span, finish, and tread material. Tube stringers are generally the more economical option, while fabricated stringers with custom profiles represent a premium option for non-standard dimensions. Contact our team for a quote based on your specific project.

A side stringer is visible, running along the outer edge of the treads as a design element in itself. A single undermount stringer is hidden beneath the treads, creating a floating appearance with no visible support structure from typical viewing angles. The choice usually comes down to whether you want the structure to be part of the visual design or invisible to it.

Yes, within engineered limits. Because a single stringer must resist twisting as well as bending, longer spans or wider treads require a stiffer profile — typically a larger tube size or a fabricated stringer with increased wall thickness. Our team calculates the required profile based on your specific span and load requirements.

Solid hardwood and engineered wood are the most common choices, but steel, concrete, and glass treads are all compatible with single undermount construction. The tread material doesn’t change the stringer engineering, so material selection generally comes down to aesthetics, maintenance, and budget.

Yes. All single undermount staircases we fabricate are engineered to meet BC Building Code Section 9.8 requirements for private stairs, covering load capacity, tread dimensions, and guardrail integration. For commercial applications, staircases are engineered to the applicable commercial code requirements for the project.

Next Steps for Your Single Undermount Stair Project

Currently planning a custom build or renovation?

Share your project details, space measurements, and design preferences with our team. We’ll discuss tube and fabricated tube stringer options, recommend the right profile for your span and load requirements, and provide guidance on timeline and budget considerations.

Working with an architect or designer?

We collaborate directly with design professionals throughout the Greater Vancouver area. Request our technical specifications, torsional load data, and profile dimensions to incorporate single undermount stringer systems into your project plans.

Exploring staircase options?

Compare our full range of modern staircase designs, including side stringers, cantilevered stringers, and double undermount configurations. Each offers distinct aesthetic and structural characteristics for contemporary spaces.

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