Ornamental Metal (C-23) · Lesson 1 of 6

Stair Stringer Layout: Riser Count, Tread Run, and Uniformity

"Stair Stringer Layout: Riser Count, Tread Run, and Uniformity" is lesson 1 of 6 in the Ornamental Metal (C-23) Learning Hub. It opens with "Layout Is Arithmetic, Not Guesswork" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Layout Is Arithmetic, Not Guesswork
  2. Pick the Riser and Tread Limits for the Building
  3. Count Risers: Divide, Round Up, Divide Again
  4. Keep Every Riser and Tread Uniform
  5. Check Rise, Width, Headroom, and Angle

The worked example in the course applies this lesson to a realistic job in 6 steps, from "Count the CBC risers" through "Check the rise limit".

What you'll be able to do

  • Explain the main idea of "Stair Stringer Layout: Riser Count, Tread Run, and Uniformity" in plain language you can use on the exam.
  • Apply this step with confidence: "Count Risers: Divide, Round Up, Divide Again".
  • Apply this step with confidence: "Keep Every Riser and Tread Uniform".
  • Apply this step with confidence: "Check Rise, Width, Headroom, and Angle".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Stair Stringer Layout: Riser Count and Runnosing line108 in total rise15 treads x 11 in = 165 in runR = 6.75 in (16)T = 11 in (15)CBC stair, side view (not to scale)CBC §1011.5.2: office / public stair108 / 7 = 15.43 round UP = 16 risersRiser = 108 / 16 = 6.75 inTreads = 16 - 1 = 15Run = 15 x 11 = 165 inStringer = √(108² + 165²) = 197.2 inAngle = atan(6.75 / 11) = 31.5°Title 8 §1626(b)(2): stair angle 30° to 50°Same 108 in rise as a house stair, CRC R318.7.5 (7-3/4 in riser max, 10 in tread min)108 / 7.75 = 13.94 round UP = 14 risers → riser = 7.714 in13 treads x 10 in = 130 in run (angle 37.6°)Round the riser count UP, then divide: both stairs passSources: 2025 CBC §1011.5.2, 1011.5.4; 2025 CRC R318.7.5.1-R318.7.5.2; 8 CCR §1626(b)(2)CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Layout Is Arithmetic, Not Guesswork

The CSLB C-23 study guide lists staircases, stringers and treads under Installation, and a stair that does not land on the real floor-to-floor rise has to be rebuilt. The code does not give you a riser count; it gives you a riser limit and a tread minimum, and you work out the count from the measured rise. The governing text is 2025 CBC Section 1011.5 for public and commercial stairs and 2025 CRC Section R318.7.5 for houses.

Step 2: Pick the Riser and Tread Limits for the Building

2025 CBC Section 1011.5.2 sets risers at 7 inches maximum and 4 inches minimum, with treads 11 inches minimum measured nosing to nosing. Exception 3 relaxes this in Group R-3 and inside Group R-2 dwelling units to a 7-3/4 inch riser and a 10 inch tread. 2025 CRC Section R318.7.5.1 prints a 7-3/4 inch (196 mm) maximum riser and Section R318.7.5.2 a 10 inch (254 mm) minimum tread for houses.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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