Summary
- Part E sets airborne and impact sound standards for separating walls and floors (E1), internal walls and floors (E2), and common parts — it bites hardest on flat conversions and new semi-detached/terraced dwellings.
- New attached dwellings need either pre-completion sound testing or registered Robust Details; conversions to flats always need pre-completion testing.
- The PD evidence that matters: the chosen compliance route recorded at Stage 3, the tested build-up specified without substitution at Stage 4, and the test certificates or RD registration in the handover pack.
What the Building Safety Act requires for Part E on non-HRB domestic jobs
Requirement E1 sets performance standards for separating walls and floors between dwellings: for new build, minimum 45 dB DnT,w+Ctr airborne and maximum 62 dB L'nT,w impact; for material change of use (flat conversions), 43 dB airborne and 64 dB impact. Requirement E2 sets a lab-tested 40 dB Rw standard for new internal walls and floors within a dwelling, and E3 covers reverberation in common parts.
As Principal Designer (BSA), your job is to fix the compliance route early and protect the tested build-up from value engineering. A separating floor that passes on paper fails on site when the resilient layer is swapped or a downlight punctures the ceiling — and the retest plus remedial works come out of someone's margin, with the paper trail deciding whose.
House extensions rarely engage E1, but a loft conversion in a semi-detached house abuts the party wall: upgrading the separating wall lining in the new roofspace is frequently required and frequently missed.
Key design risks and evidence needed (RIBA Stages 2–4)
- Stage 2: identify every separating element the works create or expose (party walls in lofts, new floors in flat conversions) and choose the compliance route: Robust Details (new build only) or pre-completion testing.
- Stage 3: coordinate flanking details — floor screeds carried through under partitions, sockets back-to-back in party walls, downlights in separating ceilings — these are where tests fail.
- Stage 4: specify the full tested build-up (product names, thicknesses, resilient layers) with a 'no substitution without acoustic review' note; book the pre-completion test with a UKAS-accredited body in the programme.
Standards and references you should be citing
- BS EN ISO 16283-1 and -2 — field measurement of airborne and impact sound insulation (the method behind pre-completion testing).
- BS EN ISO 717-1/-2 — rating of sound insulation (DnT,w+Ctr and L'nT,w figures).
- Robust Details Ltd handbook — registered constructions that exempt new attached dwellings from testing (registration must happen before work starts).
- BS 8233:2014 — internal ambient noise guidance, useful where planning conditions add acoustic requirements beyond Part E.
Compliance routes compared
| Route | Applies to | Evidence to log |
|---|---|---|
| Robust Details | New attached dwellings only | RD registration certificate (pre-start), build-up spec, site photos of key junctions |
| Pre-completion testing | Conversions; new build where RD not used | UKAS test certificates per element group, tested build-up spec |
| E2 internal elements | All new internal walls/floors in dwellings | Lab performance data for the specified build-up (40 dB Rw) |
Common pitfalls that catch out sole practitioners
- Registering Robust Details after work has started — registration must precede commencement or you are back to testing.
- Flat conversions programmed with no float for a failed test and remedials.
- Party wall linings in loft conversions omitted because 'it's an existing wall'.
- Recessed downlights and flush ceiling speakers added at fit-out, puncturing the tested separating ceiling.
Frequently asked questions
Does a house extension need sound testing?
Normally no — testing applies to separating walls and floors between dwellings (E1). But new internal walls and floors within the dwelling must meet the E2 laboratory standard of 40 dB Rw, which you evidence through the specified build-up rather than a site test.
When is pre-completion testing mandatory?
For material change of use creating dwellings (flat conversions) always, and for new attached dwellings unless the separating constructions are registered Robust Details before work starts. Tests are done by a UKAS-accredited body on a sample of plots/rooms as set out in Approved Document E.
Track this natively instead of in Word templates
PD Pathway gives small practices an automated Parts A–T relevant-requirements tracker, stage-by-stage Principal Designer checklists and one-click compliance documents — built strictly for non-HRB projects. First project free, then from £10 per project or £99/yr unlimited.