Staircase Building Regulations

The document governing spiral staircase building regulations in the UK is British Standard 5395 part 2.
This document is summarised in the table below with categories given for each spiral application and the relevant maximum riser heights and minimum widths.

The table below is for guidance only – please check with your local planning authority for confirmation.

EXTRACT FROM BS5395 part 2 Minimum Clear Tread Width Riser Height Minimum Inner


Minimum Centre


Maximum Outer Going
Category A – Small Private Stair

Secondary domestic stair intended to be used by a limited number of people who are generally familiar with the stair

600mm – typical minimum diameter 1500mm 170-220mm 120mm 145mm 350mm
Category B – Main Private Stair

Similar to category A but also providing the main access to the upper floor of a private dwelling

800mm – typical minimum diameter 1800mm

N.B – 900mm in Scotland

170-220mm 120mm 190mm 350mm
Category C – Small Semi Public Stair

Small commercial stair providing access      for up to 50 people.  Intended to be used by those generally familiar with the stair.

Centre column handrail required

800mm – typical minimum diameter 2000mm 170-220mm 150mm 230mm 350mm
Category D – Semi Public Stair

Intended to be used by large numbers of people, some of whom may be unfamiliar with the stair.  Generally providing access for more than 50 people.

Centre column handrail required

900mm – typical minimum diameter 2300mm 150-190mm 150mm 250mm 450mm
Category E – Public Stair

Large commercial stair designed to be used by many people at one time e.g. place of public assembly.

Centre column handrail required

1000mm – typical minimum diameter 2500mm 150-190mm 150mm 250mm 450mm