When sound testing is required
Requirement E1 of the Building Regulations says dwelling-houses, flats and rooms for residential purposes must resist sound from other parts of the same building and from adjoining buildings. Approved Document E turns that into a testing regime — pre-completion testing — for four cases:
- New-build houses and flats that are attached to one another
- Houses and flats formed by material change of use — the office-to-flats conversion, the house split into two
- Purpose-built rooms for residential purposes — hostels, hotels, boarding houses, halls of residence, residential homes
- Rooms for residential purposes formed by change of use
Care homes are decided case by case: if residents receive a level of care that means they are not living independently, Building Control may treat the building as hospital-type and outside the regime. Ask before you assume.
Internal walls and floors within a dwelling are a different matter: they need a laboratory-rated Rw 40 dB and are not tested on site.
The numbers
Testing is of two kinds. Airborne tests put a loudspeaker on one side of the wall or floor and measure what arrives on the other; impact tests run a tapping machine on the floor above and measure the room below. The results are expressed as DnT,w + Ctr for airborne (higher is better) and L’nT,w for impact (lower is better).
| Airborne, minimum | Impact, maximum | |
|---|---|---|
| New-build houses and flats — walls | 45 dB | — |
| New-build houses and flats — floors | 45 dB | 62 dB |
| Conversions — walls | 43 dB | — |
| Conversions — floors | 43 dB | 64 dB |
| Purpose-built rooms for residential purposes — walls | 43 dB | — |
| Purpose-built rooms for residential purposes — floors | 45 dB | 62 dB |
The purpose-built rooms-for-residential-purposes wall figure is the one people get wrong: 43 dB, not 45. Everyone assumes student accommodation and flats share a number.
How many tests
Approved Document E asks Building Control to stipulate at least one set of tests for every ten dwellings or rooms in a group or sub-group of the same construction type — on the assumption that none fail. What a “set” means depends on what is being tested:
- Houses: two tests — two airborne tests through the separating wall.
- Flats with separating floors only: four — two airborne and two impact.
- Flats with separating walls and floors: six — two airborne wall, two airborne floor, two impact.
“One in ten” is the shorthand, and it is where quotes go wrong: a site with masonry party walls on the houses and a concrete-frame block of flats has two groups, so it needs two sets before you have reached ten of anything. Tests are not carried out between a dwelling and a corridor, stairwell or hallway.
The Robust Details alternative
For new-build attached dwellings there is a way round testing. Register the plots with Robust Details Ltd before work starts — currently £40 plus VAT per dwelling — build the separating walls and floors strictly to the registered detail, and Building Control will not ask for routine pre-completion testing. Regulation 41 makes the exemption depend on notifying Building Control before work begins, with the detail reference numbers; miss that and you are back to testing.
It applies to new-build attached dwellings only. Conversions, extensions and rooms for residential purposes cannot use it — those are tested.
Who tests, and what you get
Approved Document E says testing should be carried out by a body with appropriate third-party accreditation, preferably UKAS-accredited for field measurements, and records that the government also regards members of the Association of Noise Consultants’ Registration Scheme as suitably qualified. Neither is a competent-person scheme in the Building Regulations sense — the results still go to Building Control, and Building Control decides.
Regulation 41 puts the duty on the person carrying out the work to have the testing done and to give the results to Building Control by the completion notice. The report sets out the address, the property type, the dates, who tested and their accreditation, the measured values against the applicable standards, a pass or fail for each, and the third-octave-band data behind it.
One point worth knowing: Approved Document E still cites the ISO 140 series of measurement standards, which was withdrawn in 2014. Testing is actually carried out to the current BS EN ISO 16283 series and rated to BS EN ISO 717 — the same physics, the current method.
Getting it right before we test
The Approved Document’s own guidance is blunt about where failures come from: junction detailing. Its “do not” list includes deep sockets and chases in the separating wall, sockets placed back to back, and cavity walls built off a continuous solid concrete slab. In our experience the rest of the list is service penetrations that were never sealed, mineral wool missing from a cavity, rigid bridging across a resilient layer, and a screed that runs straight into the wall. All cheaper to fix on a drawing than after a failed test. If you are unsure about a detail, send it over before the build gets there.
For testing itself: rooms on both sides essentially complete except for decoration, doors and windows in, sockets fitted, no carpet or soft floor covering for the impact tests, and access to both sides at once.
Scotland and Wales
Wales uses its own edition of Approved Document E with the same performance figures as England — 45/62 for new build, 43/64 for conversions — and the same Robust Details route.
Scotland is different in kind. Standard 5.1 of the Domestic Technical Handbook requires 56 dB airborne and 56 dB impact for new build, with 53 and 58 for conversions of traditional buildings, and the airborne figure is measured without the Ctr correction. Scotland’s 56 is not “eleven decibels stricter” than England’s 45 — it is a different quantity. Testing there is post-completion, and Robust Details (Scotland) provides the equivalent route round it.
Environmental noise surveys
For commercial projects and planning applications we also carry out environmental noise assessments — from a single air-conditioning unit to a residential scheme beside a road, railway or flight path. Surveys are reported to BS 8233:2014 for internal noise levels and BS 4142:2014+A1:2019 for industrial and commercial sound including plant, following the ProPG planning-and-noise guidance in England, to satisfy Environmental Health, Planning or Building Control — with sound-insulation recommendations where the numbers need help.
Bundle sound testing with SAP and air testing in our Compliance Pack, or see everything we do for residential buildings. Get a quote or call 01202 623236.
Common questions
What sound test results do I need to pass Part E?
For new-build houses and flats, separating walls and floors need an airborne result of at least 45 dB (DnT,w + Ctr) and floors an impact result of no more than 62 dB (L'nT,w). For dwellings formed by conversion the standards are 43 dB airborne and 64 dB impact. Purpose-built rooms for residential purposes — student halls, hotels, hostels — have their own table: 43 dB for walls but 45 dB and 62 dB for floors.
How many sound tests does my development need?
Approved Document E says Building Control should ask for at least one set of tests for every ten dwellings or rooms in each group or sub-group of the same construction — assuming none fail. A set is two tests for houses (two airborne wall tests), four for flats with separating floors only (two airborne, two impact), and six for flats with both separating walls and floors. Several construction types on one site means several sets.
Can I avoid sound testing altogether?
For new-build attached dwellings, yes — register the plots with Robust Details Ltd before work starts and build the separating walls and floors strictly to the registered detail. Building Control then does not ask for routine pre-completion testing. Registration is £40 plus VAT per dwelling. It does not cover conversions, extensions or rooms for residential purposes, and if you miss the pre-commencement notification the exemption is lost.
Who can carry out Part E sound testing?
Approved Document E says testing should be done by a body with appropriate third-party accreditation — preferably UKAS-accredited for field measurements — and the government also recognises members of the Association of Noise Consultants' Registration Scheme. Responsibility for accepting the results stays with Building Control.
When should sound testing be done?
Once the rooms either side of the separating wall or floor are essentially complete apart from decoration: floors down, ceilings in, doors and windows fitted, sockets in. Impact tests are carried out without carpet or any soft floor covering. We need access to both sides at the same time, power, and a site quiet enough to measure.
Do I need sound testing for a loft conversion or an extension?
Not if it stays one dwelling. Pre-completion testing applies to new attached dwellings, dwellings formed by a change of use, and rooms for residential purposes — so a loft conversion that creates a separate flat is tested, but one that adds a bedroom to the same house is not. Internal walls and floors within a single dwelling only have to meet a laboratory standard of Rw 40 dB and are not tested on site.
Are the standards the same in Wales and Scotland?
Wales has its own edition of Approved Document E with identical performance figures — 45/62 new build, 43/64 conversions. Scotland is different in kind: Standard 5.1 of the Building Standards Technical Handbook requires 56 dB airborne and 56 dB impact for new build, measured without the Ctr correction, so the numbers are not directly comparable with England's.