Stair & stringer guide · 7 min read
How to lay out a 2×12 stair stringer
A practical sequence for transferring rise and run measurements to a 2×12 while protecting the stringer's remaining throat.
Confirm the numbers before marking
Calculate the exact rise, run, tread count, first-rise correction, top configuration, total run, and required stock length before putting a square on the board. Make sure the chosen lumber is straight, sound, and appropriate for the installation.
Mark the repeating steps
- Set stair gauges on a framing square at the calculated exact rise and run.
- Start at one end of the 2×12 and trace the first rise-and-run corner.
- Advance the square carefully, seating each gauge against the board edge.
- Repeat for the required tread count without allowing small placement errors to accumulate.
- Mark the top cut for the selected standard or flush configuration.
- Shorten only the bottom rise by the finished tread thickness.
Protect the stringer throat
The throat is the narrowest wood left between the inside notch corner and the opposite edge of the board. Deeper rise-and-run notches leave less material. The UC2 calculator provides a planning estimate for an actual 11 1/4-inch-deep 2×12.
Estimated throat = 11.25 in − (rise × run ÷ √(rise² + run²))
A calculation does not account for damaged lumber or saw overcuts. Stop the circular saw before the inside corner and finish the cut with a handsaw or jigsaw. Confirm required capacity, span, spacing, support, and remaining material for the real project.
Make one pattern first
Cut and test-fit a single stringer before copying it. Verify bearing, attachment, upper and lower elevations, tread depth, and every finished rise. Once it fits correctly, use it as the pattern for the remaining stringers.