Types of Metal Stair Stringers

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Types of Stringers for Metal Stairs

There are many different types and styles of stringers. A staircase’s design, function, and use determine the type of style for the stairs, as well as the materials used to build them. 

Commercial and Industrial Stringers

Steel, aluminum, and stainless steel are the most commonly used materials for commercial and industrial stair stringers. These materials are commonly used in the following styles:

Double Stringers

Two stringers are fixed to each stair tread on the outside of a double staircase. They are the most common type of stair stringer for commercial and industrial stairs. A prefabricated stair system using this design can work with many types of railings. Structural steel shapes are commonly used for double stringer stairs:

  • Channel Stringers
  • Tube Stringers
  • Plates Stringers

Applications for Double Stair Stringers

Double stair stringers are often used for business egress stairs (fire escapes), industrial stairs and railings, and residential metal stairs. The two stringer design adds additional support to meet  International Building Code (IBC) for stairs and technical standards for a safe and long-lasting design.

Advantages of Double Stringer Design and Application

  • Excellent design for prefabricated stairs to facilitate installation.
  • Fire escape stairs and industrial steps with a versatile and functional design
  • To meet technical criteria, double stringer supports boost the strength of the stair.

Center Beam Stringer (Mono Stringers)

Center beam stringers are a type of mono stringer that is regularly utilized in high-end feature staircases for offices, hotels, and other high-traffic areas. A single beam, generally steel or stainless steel, sits beneath the stair treads and provides support for the steps with this form of stringer. Steel and stainless steel I-beams or tube stringers are popular shapes for center beam mono stringers.

Mono Stringer

A mono stringer staircase, as the name implies, is supported by a single heavy-duty stringer underneath the middle of the stair treads. Mono stingers are typically made of metal (steel) and are attached to each tread through a bracket system. All mono stringer staircases feature open risers to better accent the design ascetic. 

Applications for Mono/Center Beam Stringers

Center beam (mono) stringers are a form of stringer that is commonly used in monumental and feature staircases. The stringer runs along the center of the flight and is attached to the underside of the stair stringers. Mono stair stringers are widely utilized on spiral staircases in modern residences and office buildings to achieve a contemporary design.

Advantages & Disadvantages of Mono/Center Beam Stringers


  • Gives ornamental and feature staircases a high-end design look.
  • Staircases with a single stringer have the most open-air appearance of any form of stair.
  • A mono stair stringer can be used to build a variety of staircase types, including straight, U-shaped, and winder.
  • Mono stair stringers are exceptionally robust and durable, and they can be simply built to comply with most construction requirements.


  • Mono stinger staircases require a unique, engineered stringer, which is not as widely available as pre-cut closed stair stingers.
  • This staircase design is often more expensive because both the treads and stringer are likely to be specially designed.
  • Mono stringer stair cases are often not used over extended distances.
  • Construction and installation are typically more expensive.

Types of Residential Stair Stringers

Closed Stringer (Housed, Boxed or Side, Routed stringers)

Closed stair stringers are known by a variety of names, including routed, housed, side, and box stringers. This stringer is placed outside the treads and risers, containing the stairs between the two stringers. Closed stair stringers have notches in which to place the treads and risers. The tread edge is not visible with this form of stringer, and the vertical sections of the handrail (balusters and newels) are normally fastened to the top of the stringer.

Applications of Closed (routed, housed box or side) Metal Stair Stringers

Closed metal stair stingers can be utilized for stairs in a variety of settings, including houses, commercial structures, and industrial settings. Closed stair stringers are the most common application of stair stringers. For outdoor staircases, closed stair stringers are commonly used.

Advantages of Closed (routed, housed box or side) Metal Stair Stringers

Closed stair stringers can be constructed with both open or closed risers, based on the need and intended appearance. Closed stair stringer staircases are often cheaper and simpler to build. Pre-cut stringers are provided in many applications.

Twin Stringer

A twin stringer is a variant of the mono stair stringer. The mono stringer is replaced by two thin stringers in this scenario. In the middle of the stairs, they are normally spaced about 6″ apart. They can also be placed off center to produce a more eye-catching effect.

Applications for Twin Stair Stingers

Twin stair stringers, like mono stair stringers, are commonly utilized in contemporary homes and offices to achieve an open, modern design.

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