Stairs are one of the most inspected parts of any job, and one of the most dangerous if they're wrong. Small inconsistencies trip people. These are the core rules for private stairs in dwellings under Approved Document K (England). Always confirm with Building Control, as Wales, Scotland and Northern Ireland have their own regulations.
The key dimensions
| Item | Rule |
|---|---|
| Rise | 220 mm maximum |
| Going | 220 mm minimum |
| Pitch | 42° maximum |
| 2R + G | 550–700 mm |
| Headroom | 2.0 m (1.9 m on the centreline for loft conversions, sloping to 1.8 m at the side) |
| Handrail height | 900–1000 mm |
| Guarding openings | 100 mm sphere must not pass |
Laying out a flight
- Measure the total rise from finished floor to finished floor.
- Divide by the maximum riser and round up to get the number of risers.
- Divide the total rise by that number for the exact riser height.
- Treads = risers − 1. Total run = treads × tread depth.
- Check headroom along the whole flight against the floor above.
A comfortable private stair often lands around 190–200 mm rise and 240–250 mm going, giving a 2R + G of about 630–650 mm.
Common failures
- The top or bottom riser is a different height because the floor finish wasn't allowed for.
- Headroom too low under a beam or the stair opening.
- Spindles spaced just over the 100 mm limit.
- Missing handrail where one is required.
The stair calculator runs these checks as you type.
This guide is general information for estimating. It is not engineering, legal or tax advice. Check the Building Regulations and Building Control for your project.