# NI Building Regulations, Technical Booklet G: Sound
Technical Booklet G is about sound, stopping noise travelling between homes so people don't hear every word, step and flush next door. Think of it as NI's acoustic rulebook for walls and floors.
1. What Booklet G covers
- Airborne sound (voices, TV, music) between dwellings.
- Impact sound (footsteps, things dropped on floors) between storeys.
- Giving people a reasonable level of acoustic privacy and comfort in houses and flats.
You feel it on: separating walls (between semis/terraces, between flats), separating floors and ceilings (between flats above/below), and some walls/floors between dwellings and common areas.
2. Performance and constructions
Booklet G sets:
- Minimum sound insulation targets (in decibels) for airborne sound through walls/floors and impact sound through floors.
- Example constructions that normally meet those targets if built properly (masonry, timber, concrete, etc.).
On a real job: the designer picks a G-compliant construction, Building Control accepts it, and you build to that detail without cutting corners. If you change it on the fly, thinner boards, different insulation, fewer layers, you're gambling with acoustic performance.
3. Where trades quietly wreck sound performance on site
Bridging cavities and isolation
- Filling or hard-connecting things across an acoustic cavity that should stay separated.
- Fixing both sides of a "resilient" system firmly back to the same studs or structure.
Insulation
- Leaving out or under-filling acoustic insulation in separating walls/floors.
- Swapping specified dense acoustic mineral wool for cheap, light loft roll.
Floor finishes
- Laying hard flooring directly on separating floors where the design assumed carpet/underlay or a resilient layer.
- Skipping or thinning the resilient layer in a floating floor.
Flanking paths
- Continuous plasterboard or linings that run past the separating element and carry sound around it.
- Ceiling voids or service runs that bypass the acoustic line.
All of these chip away at the dB numbers G is trying to protect.
4. Conversions, highest risk for failures
Converting an existing building to flats is where Booklet G bites hardest:
- Old walls and floors usually don't meet modern sound standards on their own.
- The design will show upgrade packages: extra linings, independent studs, resilient bars, added mass, acoustic insulation.
On site:
- Don't assume "this is solid, it'll be fine" · if the drawings show upgrades, they're there because you need them.
- Follow the acoustic details exactly: correct board types and thicknesses, correct stud/bar layout, cavity depths and full-fill acoustic insulation.
- If you simplify it for ease or cost, expect trouble when testing comes.
5. Testing and sign-off
Many NI projects with flats or separating elements will require pre-completion sound testing · airborne tests through walls/floors and impact tests on floors.
From your side:
- Build assuming you will be tested.
- Keep finishes and build-ups the same as what the design assumed.
- If tests fail and you've drifted from spec, you'll likely be the one opening walls/floors back up.
6. How to stay right under Booklet G
Before you start
- Get the acoustic details from the drawings/spec and mark all separating walls/floors.
- Note any references to resilient bars, independent studs, acoustic insulation, floating floors.
While you build
- Don't change board thickness, insulation type/density, or floor build-ups without a formal redesign.
- Brief all trades not to bridge isolated linings or stuff voids with rubbish.
- Take photos before closing up to prove you followed the detail.
Near completion
- Make sure floor finishes match what the design/test assumptions used.
- Protect the building from noisy works during any tests.
- Be ready for remedial work if a test fails.
What to do next
- Read: Working in Northern Ireland · building regulations overview
- Read: NI Building Regulations · Technical Booklet F: Energy
- Read: Scottish Building Standards · Section 5: Noise (for comparison)
Sources
- Building Regulations (Northern Ireland) Order 1979 · primary legislation.
- Technical Booklet G (NI) · Sound insulation.
- BS EN ISO 140 / BS EN ISO 16283 · sound insulation testing standards.
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