Stairs by floor height · 9 ft 9 in
Stairs for a 9 ft 9 in floor-to-floor height
9 ft 9 in (117″) from floor to floor takes 17 risers of 6 7/8″ and 16 treads 11″ deep: a pitch of 32°, and two risers and a going make 24 13/16″, an easy stride. A straight flight is 14′ 8 3/8″ long and needs an opening of 11′ 6 3/4″ in the floor above.
How it’s worked out
The fewest risers that keep each at most 18 cm (7″) high, all the same: 9′ 9″ ÷ 17 = 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 9 ft 9 in is your ceiling height, the stair is taller: add the floor above it, usually 10–14″ — see stairs for 10 ft 9 in.
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 |
|---|---|---|---|---|---|
| 15 | 7 13/16″ | 9 13/16″ | 38° | 11′ 5 13/16″ | over the IRC’s 7¾″ riser |
| 16 | 7 5/16″ | 10 1/4″ | 36° | 12′ 9 9/16″ | steeper, fewer steps |
| 17 | 6 7/8″ | 11″ | 32° | 14′ 8 3/8″ | comfortable (drawn here) |
| 18 | 6 1/2″ | 11 13/16″ | 29° | 16′ 8 13/16″ | 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 9 ft 9 in: 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: 9 ft 6 in · 10 ft · all heights
Measured between finished floors. A few centimetres change the riser, not the count, until a riser passes 18 cm.