Interior Stair, 108 Inch Rise, 10 Inch Tread
An interior stair at the IRC minimum tread and a 108 in rise.
Formula SSC-2026.1
IRC check pass
Risers / treads
14 / 13
Riser inside 4 to 7.75 in
Exact riser
7 11/16 in
195.9 mm
Total run
10 ft 10 in
3,302 mm
Stringer length
14 ft 1 in
Order 16 ft 2x12
Incline
39.72°
Square 7 11/16 in rise · 10 in run
Stringers @ 16 in
3
Throat 5.14 in on a 2x12
Rise, run, and the incline are scaled from the live riser and tread. Framing-square gauges match the exact riser and the tread depth.
| Item | Net | Waste | Order | Unit price | Line total |
|---|---|---|---|---|---|
| 16 ft 2x12 | 14.73 ft cut | end cuts included | 3 boards | USD | $100.80 |
| Stringer delivery weight | 134 lb | — | 61 kg | 2.8 lb/ft planning weight | — |
| Target | Risers | Exact riser | Run | Angle | Check |
|---|---|---|---|---|---|
| 7 in | 15 | 7 3/16 in | 11 ft 8 in | 37.6° | Pass |
| 7 1/4 in | 15 | 7 3/16 in | 11 ft 8 in | 37.6° | Pass |
| 7 1/2 in | 14 | 7 11/16 in | 10 ft 10 in | 39.7° | Pass |
| 7 3/4 in | 14 | 7 11/16 in | 10 ft 10 in | 39.7° | Pass |
Show the deterministic formula
Risers = round(total rise ÷ target rise). Exact riser = total rise ÷ risers, reported to the nearest 1/16 in and in millimeters. Treads = risers − 1. Total run = treads × tread depth.
Diagonal = hypotenuse of stringer rise and total run. A dropped header uses total rise minus landing thickness. Stock is the next 8, 10, 12, 14, 16, 18, 20, or 24 ft board.
Stringers = floor(width ÷ 16) + 1, with a minimum of 2. Throat ≈ 11.25 − (riser × tread) ÷ hypotenuse.
Contractor sign-off
Project: Interior Stair, 108 Inch Rise, 10 Inch Tread
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This sheet is an estimate for ordering and layout discussion. It is not a sealed design. Confirm the quantities with a licensed local professional and the authority having jurisdiction before you buy or build.
Engineering notes
This is the same 108 in rise as a 9 ft floor-to-floor stair, with the tread held at the 10 in code minimum and a 3/4 in finish allowance in the landing thickness. Use it when the stairwell is tight and you need the shortest legal run. A deeper tread will pass the code with more comfort and a longer total run. The mount is standard, not a dropped deck header.
Code reference
IRC R311.7.5.1 limits risers to 7.75 in and R311.7.5.2 requires at least a 10 in tread. Confirm local amendments, guards, and headroom.
Field questions
- What is the total run at a 10 inch tread?
- Treads are one fewer than risers. Thirteen treads at 10 in is 130 in, or 10 ft 10 in, before wall finishes.
- Does a 10 inch tread pass?
- Yes. The check fails only under 10 in. The badge also watches the riser.
- Why is the landing thickness 3/4 inch?
- It represents a finish floor on a standard interior mount. It does not change the riser count unless you switch to a dropped header.