Total Rise: 108" (9.0 ft)
Recommended Configuration
Code IssuesRiser Height
5 1/8"
5.14 in
Warning: Stair angle below 30 degrees (too shallow)
Construction Details
Stringer Length
300 1/8"
25.0 ft
Stair Angle
21.1°
Comfortable
Comfort Score
96/100
2R+T = 24.29"
Stringer Board
2x12 x 20'
Minimum 3 stringers
All Valid Configurations (sorted by comfort)
| Steps | Riser | Tread | Total Run | Angle | Comfort | Code |
|---|
| 21Best | 5 1/8" | 14" | 23.3' | 21.1° | 96 | Issues |
| 20 | 5 3/8" | 14" | 22.2' | 22.1° | 94 | Issues |
| 15 | 7 1/4" | 10 5/8" | 12.4' | 36.0° | 90 | Pass |
| 16 | 6 3/4" | 11 1/2" | 14.4' | 32.1° | 90 | Pass |
| 17 | 6 3/8" | 12 1/4" | 16.4' | 28.8° | 90 | Issues |
| 18 | 6" | 13" | 18.4' | 26.0° | 90 | Issues |
| 19 | 5 5/8" | 13 5/8" | 20.4' | 23.8° | 90 | Issues |
| 22 | 4 7/8" | 14" | 24.5' | 20.2° | 86 | Issues |
| 14 | 7 3/4" | 10" | 10.8' | 39.7° | 81 | Pass |
| 23 | 4 3/4" | 14" | 25.7' | 19.3° | 78 | Issues |
IRC Building Code Requirements
Max Riser Height
7.75"
IRC R311.7.5.1 maximum riser
Min Tread Depth
10"
IRC R311.7.5.2 minimum tread
Min Stair Width
36"
IRC R311.7.1 clear width
Min Headroom
80" (6'8")
IRC R311.7.2 minimum clearance
Riser Variation
Max 3/8"
IRC R311.7.5.1 between any two risers
Nosing
3/4" - 1 1/4"
Required for treads < 11 inches
Comfort Rule
2R + T = 24-25
Ideal riser/tread relationship
Ideal Angle
30° - 37°
Most comfortable stair angles
Handrail Height
34" - 38"
IRC R311.7.8 measured from nosing