Staircase Stringer: Types, Cutting Procedure, and Code Requirements

Staircase stringers are essential components in stair construction, offering both support and an aesthetic framework for the stairs. A stringer is a structural member installed on either side (or sometimes the center) of a staircase, supporting the treads and risers and adding stability to the entire staircase structure. This article covers the types of staircase stringers, the procedure for cutting open stringers, and relevant code requirements to ensure safety and functionality in stair design.

Types of Staircase Stringers

Staircase stringers come in various designs to meet different aesthetic and structural needs. The three main types are routed (or housed) stringers, sawtooth (or open) stringers, and mono stringers. Each type has distinct characteristics suited to different architectural styles and functional requirements.

1. Routed or Housed Stringers Routed, or housed stringers, feature notches or grooves cut into the stringer. These notches securely hold the treads, risers, and wedges in place, supporting the entire step structure. Because the treads are held within the body of the stringer, housed stringers offer a smooth, enclosed look, which adds to the staircase’s overall durability and refined appearance. Often referred to as “Box Stringers,” they are popular in both residential and commercial stair designs where a polished, streamlined look is desired.

• Fig 1: Shows an example of Routed or Housed Stringers, highlighting the notched design that securely holds the steps in place.

1. Sawtooth or Open Stringers The sawtooth, or open stringer, has a more exposed design where the side profile reveals the outline of each step, creating a “sawtooth” pattern. This open design leaves the tread sides exposed, requiring additional finishing for a cohesive look. This type of stringer is often used in open-concept or industrial-style homes and buildings, where the structural elements are celebrated rather than concealed.

• Fig 2: Illustration of Sawtooth or Open Stringers, where the cut-out shapes along the stringer expose the treads and risers for a more architectural effect.

1. Mono Stringers Mono stringers are a unique, modern solution that uses a single, beam-like stringer to support the treads from beneath. Unlike other stringers, mono stringers lack risers and rely on a single central support, giving the stairs an airy, floating appearance. They are commonly found in minimalist or industrial design styles, where the emphasis is on open space and a light, unobtrusive look.

• Fig 3: Demonstrates the Mono Stringer design, showing the single central beam supporting the treads for an open, streamlined look.

Procedure for Cutting Open Stringers

For open stringers, precise measurements and careful cuts are crucial for both aesthetics and structural integrity. Here’s a step-by-step guide to cutting open stringers accurately.

1. Calculating Tread and Riser Dimensions The first step in creating a staircase stringer is determining the size of each tread (horizontal part) and riser (vertical part). Measure the total height between the flooring and the deck using a tape measure. For example, if the height is 56 inches, divide this by the standard riser height (commonly 7 inches) to find the number of steps: [
   \text{Total height} \div \text{Riser height} = 56″ \div 7″ = 8 \text{ steps}
   ] Next, calculate the “run” (horizontal distance) of the stairs by multiplying the number of steps by the desired tread width. Building codes generally recommend a minimum tread width of 10 inches for safe footing: [
   \text{Number of steps} \times \text{Tread width} = 8 \times 10″ = 80″ \text{ total run}
   ]

• Fig 4: Illustration of staircase dimensions, including tread, riser, and overall run, for clarity on ideal measurements.

1. Marking Tread and Riser on the Stringer After determining the dimensions, mark them on a framing square and sketch out the tread and riser layout on a 2×12-inch standard wooden plank. Ensure there’s enough space left at the top of the board (at least 7 inches) for the final riser, which can be trimmed later to fit.

• Fig 5: Shows marking of tread and riser on the framing square, which is used to transfer accurate measurements onto the board.
• Fig 6: Displays tread and riser markings on the wooden plank, showing where each step will be cut.

1. Cutting the Stringer With all lines marked, carefully cut along the lines with a circular saw. Take caution to stop the cut at each tread-riser intersection, as overcutting can weaken the stringer. Precision is essential; any overcutting at these intersections reduces the structural integrity of the stairs. Once the first stringer is cut, use it as a template for additional stringers to ensure uniformity.

• Fig 7: Shows the process of cutting along the marked lines to create the open stringer profile.

Code Requirements

Building codes provide specific guidelines to ensure stair safety and durability. These codes typically cover the live load a staircase must support, as well as dimensional restrictions such as rise, run, and vertical clearance.

1. Load Specifications Staircases need to support a designated live load, which varies depending on the building’s purpose. For residential stairs, the code specifies a live load capacity of at least 40 pounds per square foot. For commercial or more heavily trafficked spaces, this requirement increases to 100 pounds per square foot.
2. Dimensional Requirements Codes also establish minimum and maximum limits for the riser height, tread width, and total staircase width. For example, most codes recommend a minimum tread width of 10 inches to prevent trips and ensure a safe foothold. Vertical clearance requirements are also in place to allow for safe headroom as people ascend or descend the stairs. Following these requirements ensures the stairs are accessible, safe, and compliant with local building standards.

• Fig 8: Illustration of code requirements for stair rise, run, and clearance, showing how adherence to these dimensions supports safety and comfort.

Conclusion

Choosing and installing the right staircase stringer is crucial for both function and appearance. From routed stringers for a polished look to mono stringers for a modern, open design, each type serves unique architectural purposes. Accurate cutting, careful measurement, and strict adherence to building codes ensure that the staircase is not only aesthetically pleasing but also safe and structurally sound. Whether for residential or commercial applications, understanding the intricacies of stringer types, cutting techniques, and code requirements will lead to a successful and lasting staircase construction.