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For domestic stairs under Building Regulations Part K: rise must be 150-220mm, going must be 220-300mm, maximum pitch is 42 degrees, and the headroom must be at least 2000mm. The comfort formula 2R+G should be between 550-700mm. All risers and goings must be equal throughout the flight.

The 2R+G rule (also known as the Blondel formula) states that twice the rise plus the going should equal 550-700mm for a comfortable staircase. The ideal target is around 620mm. For example: with a 190mm rise and 240mm going: 2(190) + 240 = 620mm — perfect. This formula has been used since the 17th century to design comfortable stairs.

The maximum pitch (angle) of 42 degrees under Approved Document K 2013 (Table 1.1, Note 1) applies to private stairs in dwellings only. Utility and general-access (common) stairs have no explicit pitch limit in the 2013 edition — they are governed instead by the rise/going ranges and the 2R+G comfort formula. The 38-degree figure sometimes quoted comes from the superseded 1998/2010 Part K and BS 5395, not the current document. The pitch is determined by the ratio of rise to going — steeper stairs are less comfortable and more dangerous.

The minimum headroom above the staircase pitch line is 2000mm (2m) measured vertically, maintained over the full width of the flight. Approved Document K 2013 (paragraph 1.13, Diagram 1.4) allows a reduced headroom for loft conversions where the full 2m cannot be achieved: a minimum of 1.9m at the centre of the stair width, reducing to 1.8m at the side edge. Always confirm with building control.

The top of the handrail must be positioned 900mm to 1000mm measured vertically from the pitch line (the line connecting the nosings) or from the floor, per Approved Document K 2013 paragraph 1.34a. At least one handrail is required on stairs less than 1m wide, and a handrail on both sides for stairs 1m or wider (paragraph 1.34c). Handrails must be continuous and graspable, with a profile typically of 32-50mm diameter.