Building Regs Part K: Protection from Falling -- Stair Pitch, Ramp Gradient, Balustrade Height and Vehicle Barriers

Quick Answer: Approved Document K sets the dimensions for stairs, ramps, and guarding. A private stair (within a single dwelling) has a maximum pitch of 42°, rise of 150–220mm, and going of 220–300mm, with the comfort rule 2 × rise + going = 550–700mm. Headroom over a stair is 2000mm (relaxed in a loft conversion to a minimum 1.9m at the centre of the stair, reducing to 1.8m at the side). Guarding is required at any drop over 600mm: minimum 900mm high alongside stairs/landings inside a dwelling, and 1100mm for external balconies, edges, and floors; gaps must not allow a 100mm sphere to pass. Ramps run from 1:12 (short) to 1:20 (long). Part K overlaps with Part M (access) and Part B (means of escape).

Summary

Part K is "protection from falling, collision and impact" — the Approved Document carpenters, joiners, and builders reach for whenever they build or alter a staircase, balcony, landing, mezzanine, or raised deck. It is overwhelmingly dimensional: get the rise, going, pitch, headroom, and guarding numbers right and you comply; get them wrong and Building Control will not pass the work.

The single biggest source of confusion is that the numbers change with stair category and with where the guarding is. A private stair inside one home can be pitched up to 42° with a going as small as 220mm; a stair serving a place where the public goes is more generous (and gentler). Guarding alongside a domestic stair only needs to be 900mm high, but a balcony or the edge of a floor that people can fall off needs 1100mm. Mixing these up is the classic Part K failure.

Part K never works in isolation. The 2000mm headroom rule collides with loft conversions (where a relaxation exists). The stair you design under Part K must also be wide enough and gentle enough for Part M access, and it must work as a Part B means of escape (protected route, fire doors). And guarding that incorporates glass must be safety glass meeting the impact requirements. This article is the practical, dimension-first companion to the existing Part K articles — keep it on the bench when setting out a flight.

Key Facts

• Three stair categories — private (within a single dwelling), utility (limited use, e.g. access to plant/storage), and general access (everywhere else, including common stairs in flats and public buildings). Each has different rise/going/pitch limits.
• Private stair pitch — maximum 42°. This is the steepest permitted domestic stair.
• Private stair rise — 150mm to 220mm per step; all rises in a flight must be equal.
• Private stair going — minimum 220mm (in practice 220–300mm); all goings in a flight must be equal.
• 2R + G comfort rule — twice the rise plus the going must fall between 550mm and 700mm for a comfortable, safe stair. Always check this in addition to the individual rise/going limits.
• Utility stair — limited-use: max rise 190mm, min going 250mm.
• General access stair — gentlest: max rise 170mm, min going 250mm (common stairs in flats, public buildings).
• Headroom over stairs — minimum 2000mm measured vertically from the pitch line.
• Loft-conversion headroom relaxation — where 2000mm cannot be achieved in a loft conversion, reduced headroom is permitted: minimum 1900mm (1.9m) at the centre of the stair width, reducing to a minimum of 1800mm (1.8m) at the side of the stair.
• Maximum number of risers before a landing — a flight should not have more than 16 risers in a general/utility access stair (no limit on private flights, but landings still needed at top and bottom and at direction changes).
• Landings — a level landing at least the width of the stair and at least as long as the stair is wide is required at the top and bottom of every flight (with limited exceptions for the bottom step).
• Handrails — required on at least one side of a stair narrower than 1000mm, and both sides if wider; handrail height 900mm to 1000mm above the pitch line / floor.
• Guarding trigger — guarding (a barrier) is required wherever there is a drop of more than 600mm.
• Guarding height — internal stairs/landings (dwellings) — minimum 900mm.
• Guarding height — balconies, edges of floors, external — minimum 1100mm.
• 100mm sphere rule — guarding must be constructed so that a 100mm sphere cannot pass through any opening (stops a small child slipping through or getting their head stuck).
• No "ladder effect" — guarding in dwellings (and where children may use it) should not be readily climbable; horizontal rails that form a ladder are a common rejection point.
• Ramp gradients — length-dependent: 1:12 for short flights up to 2m, 1:15 up to 5m, 1:20 up to 10m; ramps need landings, edge protection, and guarding where the drop exceeds 600mm.
• Vehicle barriers — barriers to vehicle ramps, floors and roofs where vehicles have access must resist a horizontal load and be of a minimum height: 375mm for floors/roofs and 610mm for ramps.
• Safety glazing in guarding — glass used in guarding/barriers must be safety glass meeting impact requirements (BS EN 12600 classification) — overlaps with Part N/Part K critical-location glazing.

Quick Reference Table

Detailed Guidance

Setting out a private stair — the four checks

For a stair within a single dwelling, run all four checks; the design must pass every one:

1. Pitch ≤ 42°. This caps how steep the flight can be. Steeper than 42° is not a stair under Part K — it is a ladder, and only allowed in very limited situations (e.g. access to a single, non-habitable space).
2. Rise 150–220mm, equal. Every riser in the flight must be the same; an odd step that is taller or shorter is a trip hazard and a Part K failure.
3. Going 220mm minimum, equal. The going is the horizontal tread depth measured nosing-to-nosing.
4. 2R + G between 550 and 700mm. This "comfort formula" ties rise and going together. A flight that passes the individual limits but fails 2R+G will feel wrong and fail inspection.

Worked example: rise 200mm, going 230mm → pitch ≈ 41° (≤42° ✓), rise in range ✓, going in range ✓, 2R+G = 400 + 230 = 630mm (in 550–700 ✓). Compliant.

Headroom and the loft-conversion relaxation

The standard rule is a clear 2000mm measured vertically above the pitch line of the stair, along the whole flight and over landings. Loft conversions routinely cannot achieve this where the stair rises into a sloping roof. Part K provides a relaxation for loft conversions only: where 2000mm is not achievable, a reduced headroom is acceptable — applied as a minimum of 1.9m at the centre of the stair width reducing to 1.8m at the side. This relaxation is specific to loft conversions and does not apply to ordinary new stairs.

Guarding — height depends on what you are protecting against

This is where most rejections happen. Two numbers:

• 900mm — alongside stairs, landings, and the edges of floors within a dwelling (internal domestic guarding).
• 1100mm — balconies, external edges, the edges of floors generally in non-domestic buildings, and any place where the consequence of a fall is greater.

Guarding is required wherever the drop exceeds 600mm. Below 600mm, guarding is not strictly required by Part K (though it may be sensible). The infill must stop a 100mm sphere passing through any gap — this governs baluster spacing, the gap under a bottom rail, and the gap between a glass panel and the structure. In dwellings and anywhere children may be present, avoid horizontal members that create a climbable "ladder."

Ramps

Ramps are governed by both Part K and Part M. Gradient is set by the length of the flight: steeper ramps are only allowed for short rises (1:12 up to 2m), getting gentler as they get longer (1:15 up to 5m, 1:20 up to 10m). Ramps need level landings top and bottom, edge protection (a kerb or upstand to stop a wheel running off), and guarding where the adjacent drop exceeds 600mm. For accessible ramps, defer to the tighter of the Part K and Part M figures.

Vehicle barriers and loading

Where vehicles have access to a floor, roof, or ramp (car parks, decks over habitable space, basement ramps), Part K requires a vehicle barrier designed to resist a horizontal impact load. Minimum heights are typically 375mm for floor/roof edges and 610mm for ramp edges. The design horizontal load is set out in ADK Section 3 and BS 6180 (barriers in and about buildings) — this is a structural-engineer item, not a guesswork rail. Pedestrian guarding loads (line load, point load, infill load) also come from BS 6180.

How Part K interacts with Parts M and B

• Part M (access): the stair you design under Part K must also be usable. M4(2)/M4(3) dwellings and Volume 2 buildings impose additional width, handrail, and going requirements — design to the more demanding of K and M.
• Part B (fire / means of escape): a stair that forms an escape route must be protected (enclosed in fire-resisting construction with fire doors). Loft-conversion stairs almost always trigger Part B escape requirements as well as the Part K geometry.
• Glazing: glass in guarding or in a critical location near a stair must be safety glass meeting the BS EN 12600 impact classification.

Frequently Asked Questions

What is the maximum pitch for a domestic staircase?

42° for a private stair within a single dwelling. That is the steepest a normal stair can be. Anything steeper is treated as a ladder or alternating-tread stair, which Part K only permits in tightly limited situations (e.g. access to a single non-habitable loft space where a conventional stair genuinely cannot fit).

Is balustrade height 900mm or 1100mm?

Both — it depends on location. 900mm alongside internal stairs and landings within a dwelling; 1100mm for balconies, external edges, and the edges of floors in non-domestic buildings (and anywhere the fall risk is greater). The trigger for needing guarding at all is a drop of more than 600mm.

Why do my balusters have to stop a 100mm ball?

To stop a small child slipping through the gap or getting their head trapped. Part K requires that guarding be built so a 100mm sphere cannot pass through any opening — this fixes the maximum spacing between balusters and the gap under the bottom rail. It is checked physically at inspection.

Can I reduce the headroom in a loft conversion?

Yes — there is a specific loft-conversion relaxation. The standard 2000mm can be reduced where the roof slope makes it impossible, down to a minimum of 1.9m at the centre of the stair reducing to 1.8m at the side. This relaxation applies only to loft conversions, not to new-build or ground-floor stairs.

Does Part K cover ramps as well as stairs?

Yes. Ramp gradients run from 1:12 (short, up to 2m) to 1:20 (up to 10m), with required landings and edge protection. Where the ramp is part of an accessible route, Part M may impose tighter limits — design to whichever is stricter.

Regulations & Standards

• Approved Document K (2013 edition, with 2013 amendments) — Protection from falling, collision and impact: stairs, ramps, guarding (Section 1–2), vehicle barriers (Section 3), and protection from collision/impact with glazing.

• Building Regulations 2010 (as amended) — legal basis; Requirements K1–K5 in Schedule 1.

• BS 6180:2011 — Barriers in and about buildings — Code of practice (guarding and vehicle barrier design loads).

• BS 5395-1 — Stairs — Code of practice for the design of stairs with straight flights and winders.

• BS EN 12600 — Glass in building — pendulum impact test and classification (safety glazing in guarding/critical locations).

• Approved Document M & Approved Document B — interact with Part K on stair width, accessibility, and means of escape.

• GOV.UK — Approved Document K (protection from falling, collision and impact) — full text of ADK.

• Planning Portal — Building Regulations Part K — overview of stair and guarding requirements.

• legislation.gov.uk — Building Regulations 2010 — principal regulations as amended.

• BSI — BS 6180 Barriers in and about buildings — barrier and vehicle-barrier design loads.

• part k falls — companion Part K article (protection from falling, collision and impact overview).

• part k protection — companion Part K article on stair geometry and guarding heights.

• part m accessible design — Part M access requirements that interact with stair width and ramp gradients.

• part b fire — means of escape requirements for protected stairs, which overlap with Part K geometry.