Stairs by floor height · 8 ft
Stairs for an 8 ft floor-to-floor height
8 ft (96″) from floor to floor takes 14 risers of 6 7/8″ and 13 treads 11″ deep: a pitch of 32°, and two risers and a going make 24 3/4″, an easy stride. A straight flight is 11′ 11 5/16″ long and needs an opening of 11′ 7 1/4″ in the floor above.
How it’s worked out
The fewest risers that keep each at most 18 cm (7″) high, all the same: 8′ ÷ 14 = 6 7/8″. The going follows the stair builders’ rule that two risers and a going make a stride of about 63 cm (25″). There is one tread fewer than risers: the last riser goes up to the upper floor itself.
If 8 ft is your ceiling height, the stair is taller: add the floor above it, usually 10–14″ — see stairs for 9 ft.
More or fewer steps
Fewer risers make a shorter, steeper stair; more make a longer, easier one.
| Risers | Each riser | Going | Pitch | Run of a straight flight | How it walks |
|---|---|---|---|---|---|
| 12 | 8″ | 9 13/16″ | 39° | 9′ 1/4″ | over the IRC’s 7¾″ riser |
| 13 | 7 3/8″ | 9 13/16″ | 37° | 9′ 10 1/8″ | treads under the IRC’s 10″ |
| 14 | 6 7/8″ | 11″ | 32° | 11′ 11 5/16″ | comfortable (drawn here) |
| 15 | 6 3/8″ | 11 13/16″ | 28° | 13′ 9 3/8″ | comfortable |
The IRC (US homes) allows risers up to 7¾″ and asks for treads of at least 10″, 6′8″ of headroom and a width of 36″; states and towns amend it. Check the code that applies to yours.
This stair in each layout
Each drawn for 8 ft: the flights 36″ wide, the spiral 5 ft across, the square one in a 6 ft stairwell. The size is over the treads. Pick one for its plan, its sizes and its parts.
Change anything
A different width, a turn the other way, closed risers, a steel frame: open the stair in uCAD and set it in the panel, or tell the AI what the stair has to fit into.
Other heights
Other heights: 8 ft 3 in · all heights
Measured between finished floors. A few centimetres change the riser, not the count, until a riser passes 18 cm.