Stairs by floor height · 3.15 m
Stairs for a 3.15 m floor-to-floor height
3.15 m (315 cm) from floor to floor takes 18 risers of 17.5 cm and 17 treads 28 cm deep: a pitch of 32°, and two risers and a going make 63 cm, an easy stride. A straight flight is 4.76 m long and needs an opening of 3.52 m in the floor above.
How it’s worked out
The fewest risers that keep each at most 18 cm (7″) high, all the same: 3.15 m ÷ 18 = 17.5 cm. 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 3.15 m is your ceiling height, the stair is taller: add the floor above it, usually 25–35 cm.
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 |
|---|---|---|---|---|---|
| 16 | 19.7 cm | 25 cm | 38° | 3.75 m | steeper, fewer steps |
| 17 | 18.5 cm | 26 cm | 35° | 4.16 m | steeper, fewer steps |
| 18 | 17.5 cm | 28 cm | 32° | 4.76 m | comfortable (drawn here) |
| 19 | 16.6 cm | 30 cm | 29° | 5.40 m | comfortable |
Limits differ by country: England’s Approved Document K allows a rise up to 220 mm and a pitch up to 42° in a home, Germany’s DIN 18065 up to 200 mm, and both ask for 2.0 m of headroom. Check the code that applies to yours.
This stair in each layout
Each drawn for 3.15 m: the flights 1.00 m wide, the spiral 1.60 m across, the square one in a 1.80 m 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: 3.10 m · 3.20 m · all heights
Measured between finished floors. A few centimetres change the riser, not the count, until a riser passes 18 cm.