# NI Building Regulations, Technical Booklet I: Sanitary Provision
Technical Booklet I is about making sure buildings have enough toilets and wash facilities in the right places, with proper hygiene standards. It sounds basic, until someone quietly deletes a WC or opens a toilet straight into a kitchen.
1. What Booklet I covers
- How many toilets and wash basins you need in different types of building.
- Where and how they should be located and arranged.
- Basic hygiene protection · so foul water, overflows and splashing don't contaminate food, clean areas or drinking water.
You feel it on: new houses and flats (minimum sanitary provision), extensions and refurbs that add or move WCs/bathrooms/ensuites, and non-domestic jobs where WC counts and layouts are more tightly controlled.
2. Sanitary provision, "enough loos in the right places"
For dwellings: Booklet I sets the minimum, a main bathroom (bath or shower, basin, WC) for typical houses, with extra WCs/ensuites as house size and bedroom numbers go up.
For non-domestic buildings: WC and urinal numbers based on occupant load and building use (offices, shops, schools, etc.), with requirements for separate male/female or unisex and accessible WCs.
On site: you're not usually picking the numbers, the designer does that. But you must not quietly delete or downsize WCs because "the client doesn't use them much." If they're on the approved plan, they're there to meet I.
3. Layout and hygiene
Booklet I cares about where you put fittings and how you protect hygiene:
- WCs shouldn't open directly into food preparation areas without a lobby or handwash in between.
- Hand-washing facilities should be conveniently located relative to WCs.
- Surfaces, junctions and finishes in wet areas should be reasonably washable and water-resistant.
On site:
- Don't turn the only WC into an ensuite tucked away where guests or staff have to traipse through bedrooms or kitchens, unless that's clearly allowed in the design.
- Don't swap moisture-resistant linings and sensible floor finishes in wet areas for materials that will soak and rot.
- Keep cleanable, splash-resistant finishes behind basins, around baths and showers, and in WCs.
4. Protection of water supply
While detailed plumbing rules sit elsewhere, Booklet I touches on protecting drinking water from contamination:
- Fittings and layouts must not allow backflow from foul or dirty water into wholesome supply.
- Certain appliances and outlets need appropriate backflow prevention (air gaps, check valves, etc.).
On site: respect specs for air gaps and fit the correct valves and devices where detailed, don't bridge them out because "it's easier this way."
5. How I ties into Building Control
District council Building Control will look at: does the building have enough sanitary accommodation for its use and size? Are WCs and basins sensibly located? Are wet areas built with hygienic, water-resistant finishes and proper drainage?
If you've removed, moved or seriously altered bathrooms/WCs from what was approved, they can hold back sign-off until provision is acceptable.
6. Working habits
- Before you start: check the approved plan for number and position of WCs/bathrooms. Note any hygiene or lobby requirements.
- While you build: don't quietly drop a loo or basin to save cost or space. If the client wants to move or remove sanitary spaces, flag it as a compliance issue.
- At the end: make sure all sanitary facilities on the plan are actually installed, working, and finished with cleanable surfaces.
Sources
- Building Regulations (Northern Ireland) Order 1979 · primary legislation.
- Technical Booklet I (NI) · Sanitary appliances and provision.
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