Total rise from finished floor to finished floor is 108 inches, straight run, 2x12 stringers, 1-inch treads.

Stringer Layout:

• Total rise: 108"
• Number of risers: 108 ÷ 7.5" = 14.4 → 15 risers (standard max riser = 7.5", IRC R314.4)
• Actual rise: 108 ÷ 15 = 7.2" per riser
• Run: Use 1" tread + 2x12 depth (11.25") = 11.25" run (IRC R314.3.1 requires min 10" tread depth)

Layout Steps:

1. Mark 15 risers at 7.2" each on 2x12 stringer.
2. Mark 15 tread runs at 11.25" each.
3. Cut top plumb cut (15 risers × 7.2" = 108" total).
4. Bottom: Cut level for first tread installation.

Watch Points:

• Bottom: Ensure first riser aligns with floor framing; may need to adjust for subfloor thickness.
• Throat: Maintain 3.5" minimum clear depth above cut (IRC R314.3.1) – don’t overcut.
• Top: Secure with ledger or framing screws into floor structure.

Code Check:

• Max riser: 7.5" (7.2" OK)
• Min tread: 10" (11.25" OK)
• Handrail required if >2 risers (IRC R314.9).

Use a framing square or stair gauge for precise cuts. Double-check measurements before cutting.

Layout Math

• Total Rise: 108″
• Target Rise: 7″–7¾″ (IRC R311.7.5.1 max 7¾″).
• Risers: 108″ ÷ 7.5″ = 14.4 → 15 risers.
• Actual Rise: 108″ ÷ 15 = 7 3/16″ (7.1875″). ✅ Code compliant.
• Treads: 14 treads (always one less than risers).
• Run (IRC R311.7.5.2 min 10″): With 1″ treads, you need ≥1″ nosing overhang → Min 11″ cut run (yields 10″ clear tread depth + 1″ nosing). Use 11″ run.

Stringer Layout (2×12)

1. Top: Plumb cut flush to rim/header. Drop the stringer 1 1/8″ (7 3/16″ rise – 1″ tread thickness = 6 3/16″; but standard practice: drop = rise – tread thickness = 6 3/16″. Correction: For a flush top connection where the first tread sits on the stringer, drop the top plumb cut by the tread thickness (1″). The first step down is a full 7 3/16″.
2. Steps: Step off 14 treads @ 11″ run / 7 3/16″ rise.
3. Bottom: After last tread mark, drop 1″ (tread thickness) for the finish floor. Make level cut (seat cut) for bearing on floor/sill.

Critical Watch Items

• Throat Depth (IRC R502.8 / DCA 6): Minimum 5″ uncut wood below the deepest notch (inside corner of rise/run).
• Check: 2×12 actual depth = 11.25″. Max rise (7.1875″) + Max run (11″) = 18.1875″ hypotenuse. Throat = 11.25″ – (7.1875″ × sin(33°)) ≈ 5.2″. You are borderline. Do not overcut corners (use handsaw finish). If using LVLs (11.875″), throat is safer.
• Bottom Bearing: Full bearing on concrete/pressure-treated sill. Do not notch bottom for sole plate; use a 2× block or metal connector (Simpson LSCZ) to transfer shear.
• Top Connection: Positive connection to rim (Simpson LSCZ/LSSU or ledger bolts). Nails in withdrawal only = fail.
• Stringer Spacing: Max 16″ o.c. for 1″ treads (5/4 or 2×). 24