# NI Building Regulations, Technical Booklet D: Safety (Stairs, Guarding, Glazing)
Technical Booklet D is about safety on stairs, ramps, guarding and protection from falling, collision and impact, the "don't let people fall or walk into something nasty" rules.
1. What Booklet D is trying to do
It sets standards so that:
- People can move safely around the building.
- They don't fall down stairs, over edges, or out of low windows.
- They don't get badly hurt by glass or projections in "at risk" areas.
You'll feel it most on: stairs and ramps, balustrades and guarding at edges, low-level glazing and doors with glass, and windows with low sills where there's a drop outside.
2. Stairs and ramps, sizes and handrails
Booklet D gives minimum/maximum figures for:
- Rise and going (height and depth) of steps.
- Overall pitch of the stair.
- Headroom over the stair.
- Width and handrail requirements.
On site:
- You do not freelance stair dimensions. Build what's on the approved drawings, which should match Booklet D's tables.
- Risers must be consistent · no surprise tall or short steps.
- Handrails go in where the drawings show, at the correct height, and must be continuous where required · no big gaps because "it looks nicer."
- If you squeeze or stretch stairs on site to "make them fit," you're very likely off the D standard.
3. Guarding and balustrades, stopping falls
Anywhere there's a drop, stairs, landings, balconies, roofs used as terraces, external retaining walls, big internal openings, Booklet D sets:
- Where guarding is required.
- The minimum height.
- Requirements for gaps (to stop children getting through or stuck).
- Loads the guarding must resist.
Practically:
- Don't lower balustrades or parapets because a client wants a better view · if you take them under the minimum height, you're out of spec.
- Don't use spindles, glass gaps or rails with openings big enough for a kid to slip through.
- Fix balustrades properly into structure, not just face-fix with a few token screws.
- If the drawing shows guarding, you fit guarding. You don't decide "it's only a short drop" and leave it off.
4. Windows and low-level openings
Booklet D deals with people falling out of windows or through low openings:
- Where a window sill is low and there's a significant drop outside, you may need a guard rail/barrier or restricted opening.
- There are rules for "critical locations" of glass where impact or falls are a risk.
On site:
- If you're lowering sills or putting in big opening lights upstairs, check whether guarding or restrictors are now needed.
- Don't remove existing guards or restrictors without replacing the safety function.
- Any spec that calls up safety glass or guarding at a window is not optional.
5. Glazing and impact safety
Booklet D identifies zones where glass must be safety glass (toughened or laminated):
- Glass in and next to doors.
- Low-level glazing near floors.
- Glazing at the bottom of stairs or in other obvious impact zones.
On site:
- Don't swap specified safety units for standard units because they're cheaper · that's a straight fail.
- Make sure frames and beads actually support the glass as the test assumed.
- Markings/stamps on safety glass should be visible until handover so there's no doubt what's been installed.
6. Vehicle and collision protection
In some layouts, car parks, access roads close to buildings, columns near traffic, Booklet D controls:
- Barriers or bollards to protect people and structure from vehicles.
- Edge protection at car park ramps and decks.
Don't remove or downsize bollards/barriers because someone wants easier parking. Don't move them without confirming the revised position still protects people and structure.
7. How D links into Building Control and sign-off
Council Building Control in NI will look at:
- Stairs: sizes, handrails, headroom.
- Guarding: present where needed, right height, sensible gaps.
- Windows: low sills treated properly where there's a drop.
- Glass: safety units in the right places.
If you've altered any of those from the approved plans without redesign, expect them to ask questions or withhold completion until it's corrected.
8. Working habits that keep you right
Before you build
- Check the drawings for stair details, handrails, guarding, and glazing notes.
- Clock any windows with low sills and a drop outside.
While you build
- Stick to stair dimensions · don't "adjust" on site.
- Fit all guarding and handrails as drawn.
- Make sure any glass in doors/low-level positions is safety glass where required.
Before sign-off
Walk the building like a buyer with kids: anywhere they could fall, clash with glass, or trip, does it look right and solid? Fix anything wobbly, missing or obviously under-height before Building Control points it out.
If you treat Booklet D as the "people not getting hurt" section and respect it accordingly, you'll avoid some of the nastiest liability if something goes wrong later.
What to do next
- Read: Working in Northern Ireland · building regulations overview
- Read: NI Building Regulations · Technical Booklet A: Structure
- Read: NI Building Regulations · Technical Booklet C: Site preparation and moisture
Sources
- Building Regulations (Northern Ireland) Order 1979 · primary legislation.
- Technical Booklet D (NI) · Stairs, ramps, guarding and protection from impact.
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