Steel Stringer vs Welded Plate Stringer: Which to Choose

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A steel stringer is a rolled or formed profile, such as a channel or I-beam, that carries the treads and is often hidden or partly exposed. A welded plate stringer is built from a flat steel plate, typically cut, bent or welded into shape, giving a solid, clean-lined appearance. Choose based on the design look, span and load, and the fabrication and finishing route.

What Is a Steel Stringer?

A steel stringer is the inclined beam that supports the treads and risers of a staircase. In most projects it is made from a standard rolled profile such as a channel, angle or I-beam, sometimes combined with cut-out sections for the tread supports.

Because the profile is manufactured in standard sizes, the stringer is usually quick to source and predictable in strength. Its open geometry lets designers hide it behind cladding or leave it visible as a feature.

Standard profiles, predictable section properties
Good for open or industrial-style designs
Easy to combine with timber or glass treads

What Is a Welded Plate Stringer?

A welded plate stringer is made from a flat steel plate, cut to the stair profile and often stiffened with flanges or ribs. The tread connections are welded or bolted directly to the plate, giving a continuous and monolithic appearance.

This type suits designs where the stringer is a visible sculptural element. Thickness, edge treatment and stiffening are tailored to the project, so the result is custom rather than catalogue-based.

Structural Behaviour and Load

Both solutions can meet structural requirements when correctly designed, but they carry load differently. A rolled profile resists bending through its depth and flanges, while a plate stringer relies on plate thickness and stiffening ribs to control deflection and vibration.

Exact section sizes, load values and deflection limits must always be verified by the structural engineer against the applicable standards for the building. The fabricator's role is to build to the approved design and to confirm connection details.

Appearance and Design Flexibility

The visual difference is the main reason designers compare these two options. Steel stringers show a linear, engineered character, often with visible profile lines and open spaces beneath. Welded plate stringers look smooth, solid and seamless, which suits minimalist or contemporary interiors.

Plate stringers offer more freedom in curves, cut-outs and integrated handrail supports. Standard profiles are more limited, but they are efficient when the design calls for an exposed, industrial aesthetic.

Fabrication, Finishing and Installation

Steel stringers need fewer cutting and welding operations when standard sections are used, which can simplify the shop process. Plate stringers require accurate cutting, forming and welding, with careful control of distortion before finishing.

Finishing options include hot-dip galvanizing and powder coating
Plate stringers need careful handling to keep edges and welds flat
Both types must be measured on site before final fabrication

Installation should follow the approved drawings, with connections checked for alignment and level.

How to Choose Between Them

Start with the design intent: if the stair should look light and structural, a steel stringer is often the better fit; if it should look solid and sculptural, a welded plate stringer is usually preferred. Next, review span, loads, budget logic in general terms, and the time available for fabrication.

Involve the structural engineer early, share architectural drawings and photos of the reference style, and confirm the finish requirements, including corrosion protection for the building environment.

Frequently asked questions

Is a welded plate stringer stronger than a steel stringer?

Not automatically. Strength depends on the section size, plate thickness, stiffening and connections, all of which the structural engineer must verify for the specific stair.

Which option is easier to fabricate?

Steel stringers made from standard profiles are often simpler in the shop, while plate stringers need more precise cutting and welding. The best choice depends on the design and the workshop's capabilities.

Can both types be galvanized or powder coated?

Yes, both can be finished with hot-dip galvanizing or powder coating, though the finish choice should match the environment and the design's surface requirements.

Should I decide before taking measurements?

It is better to confirm the stringer type after an on-site measurement, since the actual opening, floor levels and wall conditions affect the final design and connections.

Common mistakes to avoid

Choosing a stringer type based only on appearance without checking loads, span and connections with the engineer. Also, finalizing dimensions before on-site measurement can lead to costly corrections.

Our recommendation

Decide the look first, then have the engineer confirm the section or plate thickness and stiffening before drawings are approved. Send photos and measurements early so the fabricator can suggest the most practical construction method.

Summary

Steel stringers suit exposed, engineered looks and standard profiles, while welded plate stringers suit smooth, sculptural designs. Both need engineer-verified structure and a clear finishing plan.

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