ProjectCalcWhen a guard is needed
Approved Document K (2013 edition) deals with Requirement K2, protection from falling. Paragraph 3.1 requires guarding "where it is reasonably necessary for safety to guard the edges of any part of a floor (including the edge below an opening window), gallery, balcony, roof (including roof lights and other openings), any other place to which people have access, and any light well, basement or similar sunken area next to a building", and in vehicle parks.
For stairs specifically, the trigger in dwellings is a drop: guard the sides of flights and landings when there is a drop of more than 600 mm (paragraph 1.41). For buildings other than dwellings and common access areas of blocks of flats, guarding is needed when there are two or more risers (1.40).
How high — Diagram 3.1
The heights are set by Diagram 3.1. For a single family dwelling they are short and clear:
| Location | Height of guarding (h) |
|---|---|
| Stairs, landings, ramps, edges of internal floors | 900 mm for all elements |
| External balconies, including Juliette balconies and edges of roof | 1100 mm |
| Glazing in all buildings — at opening windows (except roof windows in loft extensions, see Approved Document B1) | 800 mm |
| Glazing in all buildings — at glazing to changes of levels to provide containment | Below 800 mm |
So the working figure for a dwelling is 900 mm around a floor edge, a stair or a landing, rising to 1100 mm for an external balcony or a roof edge. Other building categories in the same diagram — factories and warehouses, residential/institutional/educational/office/public, assembly, retail — have their own columns; the "assembly" category, for example, uses 800 mm within 530 mm in front of fixed seating and 900 mm for flights elsewhere.
The window rule
The glazing row of Diagram 3.1 is the one that gets missed. At an opening window the guarding height is 800 mm — and paragraph 3.1(a) makes it explicit that the edge below an opening window is an edge to be guarded. A first-floor opening window that reaches down near floor level is therefore a guarding question, not just a glazing question.
Design and construction conditions
- You may use "any wall, parapet, balustrade or similar obstruction as guarding" (3.2(b)).
- Guarding must be able to resist, as a minimum, the loads given in BS EN 1991-1-1 with its UK National Annex and PD 6688-1-1 (3.2(c)). For further guidance on the design of barriers and infill panels the document points to BS 6180.
- Where guarding is glazed, Section 5 of the document applies as well (3.2(d)).
- In a building that may be used by children under five, guarding must prevent a 100 mm sphere passing through any opening, and must avoid horizontal rails that could be climbed (3.3).
What this changes about the build
Two decisions are set by these figures before anything is ordered. The height of the deck, balcony or landing decides whether guarding is required at all — the 600 mm drop is the trigger in a dwelling. And the height of the guard is then fixed at 900 mm or 1100 mm depending on whether it is an internal floor edge or an external balcony or roof edge.
It is also worth knowing that a guard is a structural element with a load to resist, not a decorative rail. If the guard is fixed to the deck structure or the wall, the fixing and the member sizes are part of the design.
The editions this document cites
These are British and European standards this approved document names. The edition column is the one the document itself cites; the last column is what BSI catalogues today (22 September 2026). Where the two differ, the document is citing an edition that has since been replaced or withdrawn — that is normal for an approved document, and it is why the current edition is listed beside it rather than instead of it.
| Standard | Title as published | Edition cited by the approved document | Current edition (BSI) |
|---|---|---|---|
| BS EN 1991-1-1 | Eurocode 1. Actions on structures — Specific weight of materials, self-weight of construction works and imposed loads for buildings | BS EN 1991-1-1:2002 with its UK National Annex — cited by Approved Document K | BS EN 1991-1-1:2025 — Current, Under Review. BSI currently lists both the 2002 and 2025 editions as Current, so a designer needs to check which the project is being designed to |
| PD 6688-1-1 | Recommendations for the design of structures to BS EN 1991-1-1 | PD 6688-1-1:2011 — cited by Approved Document K | PD 6688-1-1:2011 — Current (31 May 2011) |
| BS 6180 | Barriers in and about buildings. Code of practice | BS 6180 — cited by Approved Document K with no edition given | BS 6180:2011 — Current, Under Review |
Source: BSI catalogue records read at knowledge.bsigroup.com on 22 September 2026. Each title, designation, status and date in the last two columns was read from the BSI catalogue page for that standard.
Last verified 22 September 2026. Every requirement quoted on this page was read from the primary source listed below on that date, not from a summary. If a figure could not be confirmed in the primary source it is not on this page.
Where these figures come from
- Approved Document K: Protection from falling, collision and impact, 2013 edition (Requirement K2; paragraphs 1.38-1.41, 3.1-3.3 and Diagram 3.1) — GOV.UK publications, "Protection from falling, collision and impact: Approved Document K", checked 22 September 2026.
- BSI catalogue (“BSI Knowledge”) — product record for each standard listed above: title, current edition and status — knowledge.bsigroup.com, checked 22 September 2026.
Guidance only, not advice
This page is a plain-English summary of published regulations and standards, written to help you plan a job. It is not professional advice, it is not a substitute for the actual document, and it is not a building-control decision.
Building regulations are enforced by your local authority (or an approved inspector) and the facts of a particular job can change the answer. Confirm with your local building control before you start work, and where a job is structural, get it designed by a suitably qualified person. If this page and the source document disagree, the source document wins.