Rise, going and pitch
The rise is the vertical step height; the going is the horizontal distance between successive step nosings. For a private stair, Approved Document K gives a maximum rise of 220 mm, a minimum going of 220 mm and a maximum pitch of 42 degrees, alongside other dimensional and layout guidance. [2]
Those are not three independent allowances that can be combined without checking the complete stair. The chosen geometry, consistency of steps, landings and door relationships all need to be shown on the design. Different categories of stair have different dimensions. [2]
Headroom: measure the finished arrangement
The normal stair headroom guidance is 2 metres. For a loft conversion where that is not achievable, the illustrated concession permits 1.9 metres at the centre and 1.8 metres at the side in the specified sloping-roof arrangement. It is a limited loft provision, not a general rule that all stairs may have reduced headroom. [2]
Check the section with the actual floor construction and roof build-up. A staircase that fits before insulation, structural work or finishes are added may not fit in the completed space. Coordinate the stair supplier's dimensions with the building design. [3] [4]
Handrails and guarding are separate considerations
Guarding protects an open edge; a handrail supports a person using the stair. Approved Document K gives location-specific provisions. For a single-family dwelling, its guarding diagram gives 900 mm for stairs, landings and internal floor edges, and 1,100 mm for external balconies, including Juliet balconies, and roof edges. [2]
Where young children may use the building, the guidance addresses openings that would allow a 100 mm sphere to pass and arrangements that encourage climbing. Do not assess a decorative balustrade solely by its overall height. [2]
Coordinate escape and accessibility
A geometrically compliant stair does not by itself demonstrate an acceptable fire escape route. In a loft conversion, the stair and lower-floor layout need to be coordinated with the fire strategy. Accessible housing requirements can also affect circulation and approach arrangements. [5] [3] [6]
Before manufacture and installation
Confirm the finished dimensions, guarding specification and surrounding openings before ordering. Refer proposed changes back to the designer rather than allowing the installer to solve a missing space by steepening the stair. [4]
Keep the relevant parts visible for the agreed inspections, and resolve outstanding safety items before requesting completion. The final result should match the coordinated design, not merely the available opening in the floor. [7] [8]