Question 1

What is the maximum rise and minimum going for a private stair?

Accepted Answer

For a private stair (within a single dwelling), the maximum rise is 220 mm and the minimum going is 220 mm. The pitch must not exceed 42 degrees. Additionally, the rise and going must satisfy the relationship: 2R + G should be between 550 mm and 700 mm (where R = rise and G = going). These requirements are in AD-K Section 1.2 and Diagram 1.2.

Question 2

What are the dimensions for a common stair in flats?

Accepted Answer

A common stair (shared between dwellings, such as in a block of flats) has stricter requirements: maximum rise 190 mm, minimum going 250 mm, and maximum pitch 38 degrees. The minimum clear width is 900 mm (1,200 mm if the stair is a firefighting stair). These dimensions ensure safer use by a wider range of occupants.

Question 3

What headroom is required above a staircase?

Accepted Answer

The minimum headroom measured vertically above the pitch line is 2.0 m for a private stair and 2.0 m for a common stair. At the edge of the stair (landing or doorway), headroom must also be at least 2.0 m. A reduced headroom of 1.8 m is permitted on a loft conversion stair where there is insufficient space, provided the 1.8 m clearance is maintained over at least the centre of the stair.

Question 4

What height should handrails and guarding be?

Accepted Answer

Handrails on stairs must be between 900 mm and 1,000 mm above the pitch line. Guarding (balustrading) on stairs must be at least 900 mm high. On landings, balconies, and edges of floors more than 600 mm above the level below, guarding must be at least 1,100 mm high. Guarding must not have openings that would allow a 100 mm sphere to pass through (to prevent small children getting through).

Question 5

Are there different rules for loft conversion stairs?

Accepted Answer

AD-K permits a space-saving stair or alternating tread stair for a loft conversion serving a single room, provided a conventional stair cannot be fitted. These have specific design requirements. Reduced headroom of 1.8 m may be accepted where the structure limits available height. The stair must still meet fire escape requirements per AD-B, which typically means a protected enclosure.

Parameter	Private Stair	Common Stair (Flats)	Utility / Institutional
Maximum rise	220 mm	190 mm	190 mm
Minimum going	220 mm	250 mm	250 mm
Maximum pitch	42°	38°	38°
Minimum width	No AD K minimum (800 mm common convention; 600 mm loft space-saver per Diagram 1.9)	900 mm	1,200 mm
Minimum headroom	2,000 mm	2,000 mm	2,000 mm
2R + G range	550-700 mm	550-700 mm	550-700 mm

Location	Handrail Height (mm)	Guarding Height
Private stair (flight)	900-1,000	≥ 900 mm
Common stair (flight)	900-1,000	≥ 900 mm
Internal landing (private)	N/A	≥ 900 mm (external balcony: ≥ 1,100 mm)
Landing / balcony (common)	N/A	≥ 1,100 mm
Floor edges, galleries, balconies (> 600 mm drop)	N/A	≥ 1,100 mm
100 mm sphere test	N/A	Applies to all guarding

Requirement	Private Stair	Common Stair
Landing at top and bottom	Required	Required
Landing length (min.)	Equal to stair width	Equal to stair width
Max. risers in one flight	36 (no limit for private with handrails)	16 (then landing required)
Door swing over landing	400 mm clear landing must remain	400 mm clear landing must remain

Part K Stair Dimensions Reference

Stair Dimensions — Private vs Common (AD-K Table 1.1)

Handrail and Guarding Heights (AD-K Section 1.5-1.6)

Landing Requirements

Scotland & Northern Ireland

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