Basement Stair Stringer for a 9 Foot Floor-to-Floor Rise
A 9 ft 0 in floor-to-floor basement stair. Add joist depth if your ceiling is 9 ft and the floors are farther apart.
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.
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Project: Basement Stair Stringer for a 9 Foot Floor-to-Floor Rise
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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
The preset rise is 108 in, which is 9 ft 0 in from finish floor to finish floor. A room with a 9 ft ceiling is taller than that once you add the floor structure. Measure the actual finish-to-finish rise before you cut. The target is 7.5 in and the tread is 10 in, the IRC minimum. Fourteen equal risers land under 7.75 in. Headroom under the stair and the bulkhead is not calculated.
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
- Is a 9 foot ceiling the same as a 108 inch stair?
- Only if the finish floors are 108 in apart. A 9 ft ceiling plus a joist bay is a taller rise. Type the measured number.
- How many risers is 108 inches at 7.5 inches?
- 108 divided by 7.5 is 14.4, which rounds to 14 risers. Each riser is 108 ÷ 14, just under 7.75 in.
- What is the framing-square setting?
- The rise gauge is the exact riser and the run gauge is the 10 in tread. Both are printed on the blueprint.