Staircase Building Regulations UK Explained

Staircase Regulations: What You Actually Need to Know

Staircases are one of the most heavily regulated elements in a domestic build. Get the dimensions wrong and building control will reject it — which means ripping it out and starting again. The rules are set out in Approved Document K (Protection from Falling, Collision and Impact) and they're not optional.

This guide covers the key requirements for private domestic staircases in England and Wales. Scotland and Northern Ireland have their own technical standards, which are broadly similar but differ in detail. The Planning Portal provides supplementary guidance on staircase compliance.

The Key Measurements

Every staircase has three critical dimensions:

• Rise — the vertical distance from the top of one tread to the top of the next
• Going — the horizontal distance from the front of one tread to the front of the next (measured on the pitch line)
• Pitch — the angle of the staircase from horizontal

Approved Document K Limits (Private Staircase)

| Measurement | Minimum | Maximum | |---|---|---| | Rise | 150mm | 220mm | | Going | 220mm | 300mm | | Pitch angle | — | 42° |

These are the hard limits. A rise of 221mm or a going of 219mm will fail building control inspection. No exceptions.

The 2R + G Rule

The relationship between rise and going must satisfy:

2 × Rise + Going = between 550mm and 700mm

This formula ensures the staircase feels comfortable to use. A staircase that's technically within the individual rise and going limits can still fail if the 2R+G formula doesn't work out.

Example: Rise of 190mm, going of 250mm:

2 × 190 + 250 = 630mm — within range, so it passes.

Example: Rise of 220mm, going of 220mm:

2 × 220 + 220 = 660mm — within range, passes.

Example: Rise of 220mm, going of 300mm:

2 × 220 + 300 = 740mm — exceeds 700mm, so it fails.

The Staircase Calculator checks all of these values automatically. Enter your floor-to-floor height and the available going, and it works out the rise, number of treads, pitch angle, and whether it passes the 2R+G check.

Working Out Your Staircase

Step 1: Measure Floor-to-Floor Height

This is the total vertical distance from the finished floor level of the lower storey to the finished floor level of the upper storey. Include carpet, tiles, or whatever the final floor finish will be.

A typical floor-to-floor height is 2,600mm (2.4m ceiling + 200mm for joists and flooring above).

Step 2: Calculate Number of Risers

Divide the floor-to-floor height by your target rise:

2,600 ÷ 190 = 13.7

Round to the nearest whole number: 14 risers (you can't have a partial step).

Step 3: Calculate Actual Rise

2,600 ÷ 14 = 185.7mm per rise

Check: 185.7mm is between 150mm and 220mm — it passes.

Step 4: Work Out Number of Treads

The number of treads is always one less than the number of risers (because the top floor acts as the final tread):

14 - 1 = 13 treads

Step 5: Calculate Total Going

If each going is 245mm:

13 × 245 = 3,185mm total going

This is how much horizontal space the staircase occupies. Check you have room for it.

Step 6: Check 2R+G

2 × 185.7 + 245 = 615.4mm — within 550–700mm, so it passes.

Step 7: Check the Pitch Angle

Pitch angle = arctan(Rise ÷ Going)

arctan(185.7 ÷ 245) = 37.2° — under 42°, so it passes.

Headroom

The minimum headroom measured vertically above the pitch line is:

| Staircase Type | Minimum Headroom | |---|---| | Main staircase | 2,000mm | | Loft conversion (reduced headroom allowed) | 1,900mm at centre, 1,800mm at side |

Headroom is measured from the nosing line (the front edge of the treads) to the underside of the ceiling, bulkhead, or any obstruction above.

The loft conversion reduced headroom allowance only applies where there genuinely isn't enough space to achieve 2,000mm. Building control won't accept 1,900mm headroom on a new-build staircase — it's specifically for conversions of existing buildings.

Width

| Staircase Type | Minimum Width | |---|---| | Main staircase | No minimum stated in Part K, but practically 800mm+ | | Building Regs Part B (fire escape) | 825mm clear between walls, or between wall and balustrade |

In practice, most domestic staircases are built at 860mm (to suit standard stair parts) or wider. Anything under 800mm feels cramped and can cause issues with furniture delivery.

Handrails

• Handrail required on at least one side if the staircase is less than 1m wide
• Handrails required on both sides if the staircase is 1m wide or more
• Handrail height: 900mm to 1,000mm measured vertically from the pitch line (nosing)
• The handrail must extend 300mm horizontally beyond the top and bottom nosings where possible
• Handrail must be graspable — a round section of 32–50mm diameter is ideal

Balustrades and Guarding

Any staircase, landing, or floor edge where there's a drop of 600mm or more needs guarding (a balustrade or wall).

| Requirement | Dimension | |---|---| | Minimum balustrade height (staircase) | 900mm above pitch line | | Minimum balustrade height (landing) | 1,100mm above landing floor level | | Maximum gap between spindles | 100mm | | No sphere of 100mm to pass through | Applies to all guarding |

The 100mm rule means a 100mm sphere must not be able to pass through any opening in the balustrade at any point. This stops small children getting their heads stuck.

If you're spacing spindles, the Spindle Calculator works out the exact centres based on your spindle width and the total balustrade length.

No Climbing Aids

The balustrade design must not include horizontal rails or features that a child could use to climb. This means:

• Vertical spindles — always acceptable
• Horizontal rails — generally not acceptable for domestic staircases
• Glass panels — acceptable (no climbing aids)
• Mesh or perforated panels — check that no openings exceed 100mm and there are no footholds

Winders and Turns

If your staircase turns a corner, you have options:

Quarter-Turn with Winders

Winder treads (triangular or kite-shaped treads at the turn) must have a going of at least 50mm at the narrow end and meet the minimum going requirement measured at the centre of the tread.

Half Landing

A half landing is a flat platform at the turn. It must be at least as wide as the staircase and as deep as the staircase is wide. No door should swing across a landing and reduce the clear width to less than 400mm.

Alternating Tread Stairs

Only permitted for loft conversions serving a single habitable room (typically a loft bedroom). Not acceptable as a main staircase.

Loft Conversions: Special Rules

Loft conversions have relaxed rules to account for limited space:

• Alternating tread stairs are permitted if they serve a single room
• Reduced headroom of 1,900mm is acceptable where full headroom cannot be achieved
• The staircase must still meet the standard rise, going, and 2R+G requirements
• A 30-minute fire door (FD30S) is required at the bottom of the loft stairs as specified in Approved Document B
• Smoke detection must be provided (interlinked alarms on every level)

Open Risers

Staircases can have open risers (no vertical board between treads), but:

• The gap between treads must not allow a 100mm sphere to pass through
• In practice, this means the overlap between treads must be at least the difference between the rise and 100mm
• Open-riser stairs are not permitted on staircases used as fire escape routes in flats

Building Control Sign-Off

Building control will check your staircase at two stages:

1. First fix — trimming, structural support, carriage beams. Before plastering.
2. Final inspection — finished staircase with treads, risers, handrails, balustrade, and any fire doors.

Have your dimensions calculated and written down. If building control queries your staircase, being able to show the 2R+G calculation and pitch angle saves time and debate.

Quick Summary

1. Rise: 150–220mm, Going: 220–300mm, Pitch: max 42°
2. 2R+G must be between 550mm and 700mm
3. Minimum headroom: 2,000mm (1,900mm for loft conversions)
4. Handrail at 900–1,000mm on at least one side
5. Balustrade gaps: maximum 100mm
6. Landing or guarding height: 1,100mm minimum

The Staircase Calculator checks all Part K requirements automatically — enter your floor-to-floor height and it gives you the rise, going, pitch angle, and compliance check.