In a single family dwelling, guarding to stairs, landings and internal floor edges must be at least 900mm high, rising to 1100mm at external balconies and roof edges. In most other buildings it is 900mm on flights and 1100mm elsewhere. Where under fives may be present, a 100mm sphere must not pass through any opening.
Those figures come from Approved Document K, which covers protection from falling, collision and impact. Below is the detail, and the parts people most often get wrong.
Guarding heights under Approved Document K
The heights depend on the type of building and where the guarding sits.
| Building | Location | Minimum height |
|---|---|---|
| Single family dwellings | Stairs, landings, ramps, edges of internal floors | 900mm |
| Single family dwellings | External balconies, including Juliette balconies, and roof edges | 1100mm |
| Factories and warehouses (light traffic) | Stairs and ramps | 900mm |
| Factories and warehouses (light traffic) | Landings and edges of floors | 1100mm |
| Residential, institutional, educational, office and public buildings | All locations | 900mm on flights, otherwise 1100mm |
| Assembly | Within 530mm in front of fixed seating | 800mm |
| Assembly | All other locations | 900mm on flights, elsewhere 1100mm |
| Retail | All locations | 900mm on flights, otherwise 1100mm |
The most common error we see on drawings is applying the domestic 900mm to a balcony. In a dwelling, the moment guarding is at an external balcony or roof edge it becomes 1100mm.
The 100mm sphere rule
Where a building may be used by children under five during normal use, Approved Document K asks for two things:
- A 100mm sphere must not be able to pass through any opening in the guarding, so a child cannot become trapped.
- Horizontal rails should be avoided, so guarding cannot readily be climbed.
That second point rules out a lot of classic horizontal wire and rail designs in residential and educational settings. Vertical balusters at appropriate centres, or glass infill, are the usual answers.
What loadings must a balustrade resist?
Approved Document K does not set the loads itself. It points to BS EN 1991-1-1 with its UK National Annex and PD 6688-1-1, and notes that further guidance on the design of barriers and infill panels is in BS 6180.
The horizontal line loads sit in Table NA.8 of the UK National Annex. For orientation, areas within a single family dwelling are designed to a 0.36 kN/m line load, while other residential areas and the balconies and roof edges of dwellings step up to 0.74 kN/m. Higher categories apply to retail, assembly and areas subject to crowd loading.
Two practical points. The line load, the infill panel load and the point load are considered separately rather than added together. And because these values change between categories and editions, they should be read from the National Annex and BS 6180 for the specific project rather than lifted from a website, including this one.
Handrails, and when guarding is required at all
Related requirements that come up on the same drawings:
- Handrail height is 900mm to 1000mm from the pitch line or floor.
- A handrail is needed on both sides where stairs are 1000mm or wider.
- In buildings other than dwellings, where full height structural guarding is present, a second lower handrail at 600mm is required.
- Handrail profile: circular 32mm to 50mm diameter, or non circular 50mm wide by 39mm deep with a minimum 15mm radius.
- Guarding is required at the sides of flights and landings where there are two or more risers in buildings other than dwellings, or a drop of more than 600mm in a dwelling.
Glass balustrades
Glass does not change the heights or the loadings, and that is the point people miss: a frameless glass balustrade must still meet the same guarding height and resist the same loads as a metal one. What changes is how it is achieved, through glass specification, fixing detail and whether the design relies on the glass itself or on a handrail for containment.
Approved Document K also sets an 800mm threshold for glazing at changes of level where containment is needed. If glazing sits below that, it needs to provide containment.
We design and install balustrade systems in steel, stainless and glass across London and Hertfordshire, and we work from the structural engineer’s loading schedule rather than assuming a category.
Frequently asked questions
How high does a balcony balustrade need to be?
1100mm at an external balcony or roof edge, including Juliette balconies, in a single family dwelling. In most other building types, 1100mm applies away from flights of stairs.
Are horizontal rails allowed on a balustrade?
Where children under five may be present, Approved Document K says horizontal rails should be avoided because they can be climbed. In other settings they are not prohibited, but the 100mm opening rule and the loadings still apply.
Does Part K apply to an existing balustrade?
Approved Document K applies to new work and to alterations covered by the Building Regulations. An existing compliant balustrade does not have to be upgraded simply because guidance has moved on, but if you are altering it, the current requirements apply to the work.
Written by Daryl Griffiths, Managing Director, MG Group. Heights and rules quoted from Approved Document K, 2013 edition (England). Loadings per BS EN 1991-1-1 with its UK National Annex, PD 6688-1-1 and BS 6180. Checked August 2026. General guidance only, not a substitute for project specific structural design.
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