How Does a Stair Stringer Work?

Purpose

• The stringer creates the framework for the set of stairs. The stringers establish the rise and run, or the height and depth of each stair. The stringers attach to the landings at both the top and bottom of the staircase. When the stringers are built from sturdy lumber and attached to the landing, the staircase has a strong, stable base.

Design

• A stringer is essentially a board with notches cut into it for each step. The triangular cutouts are measured based on how high and deep you want the stairs. The treads lay on top of the tread notches and are nailed in place. If the cuts aren't measured and cut accurately, your stair treads may not be level or your steps may be different heights.

Construction

• The best stringers come from high-quality, straight boards to enable you to cut a straight stringer. Usually, a straight pine or Douglas fir 2-by-12 with very few knots will suffice. The first stringer involves the most work because you need to measure each of the notches to establish the rise and run of the staircase. Local building codes establish the requirements for the rise and run for your stairs. Once the first stringer is cut and tested to ensure it will work, you can use it as a template for the other stringers. The stringers are then secured to the landing with screws and brackets for a secure hold.

Stair Completion

• Once the stringers are secured to the landing, the treads are added. On deck stairs, each tread is often made from two 1-by-6 boards side-by-side with a small gap between them to allow for drainage. The treads hang over the stringers by at least 1 inch on each side. The treads are nailed or screwed into the stringers.