Stairs by floor height · 10 ft 9 in
Stairs for a 10 ft 9 in floor-to-floor height
10 ft 9 in (129″) from floor to floor takes 19 risers of 6 13/16″ and 18 treads 11 7/16″ deep: a pitch of 31°, and two risers and a going make 25″, an easy stride. A straight flight is 17′ 1 1/2″ long and needs an opening of 12′ 1 5/8″ in the floor above.
How it’s worked out
The fewest risers that keep each at most 18 cm (7″) high, all the same: 10′ 9″ ÷ 19 = 6 13/16″. 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 10 ft 9 in is your ceiling height, the stair is taller: add the floor above it, usually 10–14″ — see stairs for 11 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 |
|---|---|---|---|---|---|
| 17 | 7 9/16″ | 9 13/16″ | 38° | 13′ 1 1/2″ | treads under the IRC’s 10″ |
| 18 | 7 3/16″ | 10 5/8″ | 34° | 15′ 11/16″ | comfortable |
| 19 | 6 13/16″ | 11 7/16″ | 31° | 17′ 1 1/2″ | comfortable (drawn here) |
| 20 | 6 7/16″ | 11 13/16″ | 29° | 18′ 8 7/16″ | 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 10 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: 10 ft 6 in · 11 ft · all heights
Measured between finished floors. A few centimetres change the riser, not the count, until a riser passes 18 cm.