Approved Document K (Stairs & Balustrades): What Homeowners Need to Know

Part K is divided into sections covering:

• K1 — Stairs, ladders and ramps: design rules for domestic staircases including pitch, rise, going, headroom and handrails.
• K2 — Protection from falling: guarding (balustrades) on stairs, landings, balconies and raised floors.
• K3 — Vehicle barriers: guarding for car parks and areas where vehicles could fall.
• K4 — Protection from collision with open windows: limiting the risk of people walking into protruding windows.
• K5 — Protection from impact with glazing: addressed in conjunction with Approved Document N.

For a domestic staircase (private stair), Approved Document K requires:

• Maximum pitch: 42°
• Rise (vertical height of each step): 220 mm maximum, 150 mm minimum
• Going (horizontal depth of each step): 220 mm minimum
• Relationship: 2 × Rise + Going must be between 550 mm and 700 mm
• Headroom: minimum 2,000 mm above the pitch line, or 1,800 mm for loft conversion stairs
• Width: no minimum in Part K for private stairs, but 800 mm is common practice

All steps on a single flight must have equal rise and equal going. Open risers are not permitted where there are children under 5 (unless the opening is less than 100 mm).

Handrails must be provided on at least one side of any stair with more than two risers, at a height of 900 mm measured vertically above the pitch line (or 1,000 mm on a landing).

Guarding (balustrades) is required wherever there is a drop of more than 600 mm from a floor or raised area. Key requirements:

• Minimum guarding height: 900 mm for stairs; 1,100 mm for balconies and flat roofs accessible for maintenance
• Guarding must be designed so that a 100 mm sphere cannot pass through any opening (to prevent a child’s head becoming trapped)
• Guarding must not be climbable (no horizontal rails that act as a ladder)

Standard stair headroom of 2,000 mm is often impossible to achieve in a loft conversion due to the sloping roof. Part K allows a reduced headroom of 1,800 mm for loft conversion stairs, measured on the centre line of the stair. At the edges, the headroom can reduce further to 1,900 mm at the side of the stair where the ceiling slopes.

If even 1,800 mm cannot be achieved, a fixed alternating tread stair (sometimes called a ‘paddle stair’) may be used as an alternative. Building control will need to agree this solution.

If your extension includes a balcony (a projecting platform) or a Juliet balcony (a full-height opening with a barrier in front of it), Part K guarding requirements apply:

• Full balcony: guarding at least 1,100 mm high, designed to prevent climbing and with no gaps exceeding 100 mm
• Juliet balcony: the barrier across the full-height opening must be at least 1,100 mm high; glazed barriers are popular but must comply with Approved Document N for safety glazing

Bear in mind that a balcony overlooking a neighbour’s garden may require planning permission due to overlooking concerns, even if it qualifies as permitted development in terms of size.