Pre-completion sound testing is the on-site acoustic measurement required to demonstrate that a new residential building or conversion meets Part E of the Building Regulations before it can be occupied. Tests measure airborne sound insulation (through walls and floors) and impact sound insulation (through floors). The pass thresholds for new builds are DnT,w + Ctr ≥ 45 dB for airborne sound and L'nT,w ≤ 62 dB for impact sound; for conversions, 43 dB and 64 dB respectively. Testing must be carried out by an accredited body: NOVA Acoustics holds UKAS accreditation (No. 8568) for sound insulation testing. If a test fails, building control sign-off cannot be granted until remediation is completed and a passing re-test is achieved.
Pre Completion Sound Testing Explained
Quick Take
Pre-completion sound testing is the on-site acoustic measurement required to demonstrate that a new residential building or conversion meets Part E of the Building Regulations before it can be occupied. Tests measure airborne sound insulation (through walls and floors) and impact sound insulation (through floors). The pass thresholds for new builds are DnT,w + Ctr ≥ 45 dB for airborne sound and L’nT,w ≤ 62 dB for impact sound; for conversions, 43 dB and 64 dB respectively. Testing must be carried out by an accredited body: NOVA Acoustics holds UKAS accreditation (No. 8568) for sound insulation testing. If a test fails, building control sign-off cannot be granted until remediation is completed and a passing re-test is achieved.
What is Pre-Completion Sound Testing?
Pre-completion sound testing is how Part E of the Building Regulations is demonstrated in practice. It is a site measurement, carried out in the completed building before anyone moves in, that quantifies how well the separating walls and floors actually perform.
The word “actually” is doing real work in that sentence. Manufacturers publish laboratory measured performance figures for their products (Rw values), but on-site performance is always lower than lab performance. Flanking transmission, workmanship variation, and the acoustic characteristics of the specific rooms all take their toll. Pre-completion testing exists to confirm that the building as built, not just the products as specified, meets the required standard.
The metrics tested on site reflect this. Airborne performance is measured as DnT,w + Ctr and impact performance as L’nT,w; both are field measurements that account for real-world conditions, and both differ from the Rw values quoted on product data sheets. If you have ever wondered why a wall specified with a 55 dB Rw product can fail a 45 dB site test, that gap is the answer.
Testing is required in England under Part E and Approved Document E (ADE). Scotland, Wales, and Northern Ireland have their own equivalent requirements under their respective building standards; Scotland’s are notably more stringent. Results go to the local building control body, and the development cannot receive final sign-off or be occupied until a satisfactory result has been provided. NOVA’s sound insulation testing service covers the full process from booking to building control submission.
For a comprehensive guide to achieving Part E compliance, including the soundproofing principles, construction types, and common reasons for test failure, see our guide to passing Part E of the Building Regulations.
Who needs to carry out pre-completion sound testing?
The responsibility for commissioning testing sits with the owner or developer, not the contractor, although in practice the developer often asks the contractor to manage the process.
Testing is required for:
- Developers of new residential buildings with separating walls or floors between different occupancies: semi-detached and terraced houses, flats, and apartment blocks
- Developers converting non-residential buildings (offices, warehouses, commercial premises) to residential use, since material change of use triggers Part E
- Landlords and developers converting single-family homes to HMOs; material change of use applies here too, and our HMO sound testing guide covers the specifics
- Student accommodation and similar purpose-built residential accommodation with separating constructions between individual units
Testing is not required for single detached houses with no shared walls or floors, which fall outside the scope of Part E, or for developments built to a registered Robust Detail specification, which are exempt from testing subject to compliance with the RD scheme (more on this below).
Two practical points catch people out. First, the testing must be carried out by an accredited body, and building control authorities in England increasingly require UKAS accreditation specifically. Not all testing companies hold it, and it is a meaningful quality threshold rather than a badge. Second, testing must happen before occupation. Retrospective testing in an occupied building is far more difficult and expensive, and building control may not accept it as satisfying the pre-completion requirement.
Unsure whether your project requires pre-completion sound testing? NOVA Acoustics can advise quickly. Get in touch for a no-obligation scoping conversation.
What does a pre-completion sound test involve?
There are two test types, and they measure different things.
Airborne sound insulation tests measure how well the separating construction resists sound transmitted through the air: voices, music, television. A loudspeaker generates a broadband noise signal in the source room, and sound levels are measured in both the source room and the receiving room on the other side of the partition. The difference, normalised for the receiving room’s reverberation time, gives the DnT,w + Ctr value. Airborne tests apply to separating walls between dwellings and separating floors between dwellings.
Impact sound insulation tests measure how well a separating floor resists impact sound: footsteps, dropped objects, furniture being moved. A calibrated tapping machine (a standardised device that applies five hammers to the floor at a fixed rate) runs on the floor above, and the tester measures the sound levels generated in the room below. The lower the measured level, the better the floor performs. Impact tests apply to separating floors only; they are not relevant to walls.
Test combinations by property type
Houses. A set comprises two airborne tests, ideally on the separating walls between bedrooms and between living rooms of the adjoining properties. No impact tests are needed because houses typically have no separating floors.
Flats. A full set includes two airborne tests and two impact tests on the separating floor (tested in both directions), plus two airborne tests on the separating wall. The combination reflects how flats are actually lived in: footstep noise from above and speech or music from adjacent units are both part of the acoustic picture.
Conversions. The test combination mirrors new build flats, with airborne and impact tests on separating floors and airborne tests on separating walls, but the lower pass thresholds apply.
What the tester needs
The building must be substantially complete: finishes in place, plasterboard taped and filled, floor finishes laid in most cases, and services installed. An incomplete building can produce misleadingly poor results. The tester needs access to both sides of every separating construction being tested, and the rooms should be empty of furniture and loose floor coverings for the duration.
What to expect on the day
If you have never been through a sound test, here is how a visit actually runs.
Before the tester arrives. Make sure the building is at the right stage: partitions finished, doors and windows installed and closable. Clear both rooms of loose items that could rattle during testing. Confirm access to both sides of every construction being tested. Turn off mechanical ventilation, fans, and anything else generating noise in or near the test areas; background noise is one of the most common causes of inconclusive results and can force measurements to be paused or repeated. Sound insulation testing should be carried out on the structural subfloor, without cosmetic finishes such as carpet or loose-laid LVT in place. The exception is where the flooring forms an integral part of the floor build-up, for example glued-down LVT, in which case it should be installed before the test.
On the day. The tester arrives with calibrated sound level meters, a loudspeaker for the airborne tests, and a tapping machine for the impact tests. All equipment is checked against a calibration device before and after each session. Each airborne test pair takes roughly 15 – 20 minutes: speaker in the source room, level readings on both sides, plus a reverberation time measurement in the receiving room to normalise the result. Each impact test takes a similar time, with the tapping machine repositioned at multiple locations on the floor above. A standard flat set (two impact, four airborne) typically takes 2 – 3 hours on site; a house set (two airborne) takes 1 – 2 hours. Multiple sets take proportionally longer.
During testing. The tester will ask for quiet: no construction activity, machinery, or conversation in or near the rooms while measurements run. A lorry passing or a power tool starting mid-measurement may mean repeating that measurement. Results are usually calculated on site, so the tester can normally indicate pass or fail before leaving, with the formal written report to follow.
After testing. The report contains the measured DnT,w + Ctr and L’nT,w values for each test, a comparison against the Part E thresholds, and a pass or fail statement for each. It goes to the local building control body. If everything passes, sign-off can proceed. If anything fails, sign-off is withheld pending remediation and re-test.
Pass and fail criteria: the numbers that matter
New build:
- Airborne sound insulation (walls and floors): DnT,w + Ctr ≥ 45 dB. Higher is better.
- Impact sound insulation (floors): L’nT,w ≤ 62 dB. Lower is better.
Material change of use (conversions):
- Airborne sound insulation: DnT,w + Ctr ≥ 43 dB. The slightly lower threshold reflects the acoustic constraints of upgrading existing structures.
- Impact sound insulation: L’nT,w ≤ 64 dB.
Rooms for residential purposes:
- Approved Document E also sets separate criteria for rooms for residential purposes, such as student accommodation, hotel rooms and houses in multiple occupation. These largely mirror the standards above, with one difference: for new build walls, the airborne requirement is DnT,w + Ctr ≥ 43 dB rather than 45 dB. Floors in new builds, and both walls and floors in material change of use, follow the same thresholds as their purpose-built dwelling equivalents.
DnT,w + Ctr is the on-site weighted level difference with a Ctr correction that accounts for low frequency noise such as traffic and music, which makes it more stringent than DnT,w alone. L’nT,w is the weighted standardised impact sound pressure level; the lower the value, the better the floor resists impact transmission.
One nuance matters more than any of the numbers: the thresholds are minimums, not quality targets. A result of exactly 45 dB is a pass, but only just, and a development designed to achieve exactly the minimum leaves no margin for workmanship variation. Good acoustic design targets a comfortable margin above the minimum, typically 48 to 50 dB for airborne performance, so the building passes on the day regardless of minor construction variation. A marginal pass is also worth thinking about from the occupant’s side: technically compliant can still mean acoustically uncomfortable, and that lands on the developer’s reputation.
A note on floor coverings: impact testing is carried out on the structural subfloor, without cosmetic finishes such as carpet or loose-laid LVT in place, so the floor build-up must achieve the threshold in its own right. The exception is where a covering is an integral, glued-down part of the floor construction, in which case it is tested as part of the completed build-up. Either way, a soft finish added after testing cannot be relied on to achieve compliance; the structural floor system needs to meet the standard on its own.
For a detailed explanation of the acoustic metrics used in Part E testing, including the difference between Rw (laboratory) and DnT,w (field) values, see our guide to Rw vs DnT,w.
How testing is sampled across a development
Part E allows sample testing rather than testing every unit, which is commercially significant on larger developments.
The standard approach is one set of tests per separating construction type per construction run, where a construction run is a continuous sequence of identical separating constructions built without a significant break in the programme. On a development of 20 identical flats built as a single programme, one set covering the floor and wall construction may suffice; a pass is treated as representative of that construction type across the development. If any subsequent unit differs materially from the tested one (a different subfloor, a different wall build-up), further testing may be required.
Where construction types are more varied, or where the building control body has specific concerns, testing every 1 in 10 properties of each type may be required instead. That is at building control’s discretion, which leads to the practical rule: agree the sampling strategy with building control before testing commences. Do not assume an approach is acceptable without confirmation.
The sampling logic cuts both ways. If a test fails, the failure applies to all units of that construction type in the development, not just the tested unit, and remediation may be required across multiple units.
The Robust Details alternative
Robust Details (RD) is a scheme that exempts registered plots from pre-completion testing, provided the construction is registered with Robust Details Ltd before work starts and built exactly to an approved specification. The developer registers plots on the Robust Details website, pays the registration fee per plot, and commits to the registered specification; an RD inspector visits during construction to verify it is being followed.
RD makes sense for volume housebuilders constructing large numbers of identical plots to the same specification, where avoiding multiple test sets saves real money at scale. It is generally not appropriate for conversions (which are not eligible), bespoke or non-standard construction types with no approved RD specification, or one-off developments where the registration cost and inspection process are disproportionate.
The critical risk is that the exemption is conditional on the construction matching the registered specification exactly. Product substitutions, workmanship deviations, or omitted details can void it. If building control later requires testing, for instance following a complaint, a failed result carries no fallback.
It is also worth being clear-eyed about what RD guarantees. Approved specifications are designed to achieve Part E when built correctly, but they are minimum-compliance specifications rather than high-performance ones. Occupants in RD-exempt developments can still experience poor acoustic conditions if the construction sits at the lower end of the margin. Our Robust Details standard reference covers the scheme in more detail.
For a comparison of Robust Details vs full acoustic design, including eligibility, costs, and when each is appropriate, see the relevant section in our Part E guide.
What happens if you fail?
A failed test means building control sign-off cannot be granted for the affected units until the issue is resolved and a passing re-test is achieved. The units cannot be occupied in the interim, so a failure late in a programme has immediate commercial consequences.
The first step is to speak to an acoustic consultant before touching anything. Remediation aimed at the wrong cause wastes money and may not fix the problem, and the right response depends entirely on why the test failed.
The test report gives the starting point. The gap between the measured result and the threshold indicates severity: a result of 42 dB against a 45 dB airborne target is a 3 dB shortfall, relatively small and often addressable through targeted interventions such as resealing perimeters, treating flanking paths, or adding a plasterboard layer. A result of 35 dB points to something more fundamental: wrong products, missing decoupling, inadequate mass, and a more substantial remediation programme.
The common causes, and what they tend to indicate:
- Poor airtightness. Gaps in the perimeter seal, back-to-back sockets, unsealed service penetrations. Usually produces a moderate shortfall across the frequency range.
- Flanking transmission. Sound travelling around the partition rather than through it. Can cause a failure even when the separating construction itself is correctly built, and is identified by the pattern of results across frequency bands.
- Incorrect products or substitutions. Standard mineral wool rolls where acoustic slab was specified, the wrong plasterboard density, a missing resilient bar layer. Often produces a larger shortfall.
- Incorrectly installed resilient systems. Resilient bars or clips that have been bridged (screwed through into the joist or stud behind) lose their decoupling effect entirely, and can cause catastrophic failure even when everything else is right.
After remediation, a further test is required to demonstrate compliance, at additional cost. Building control will not accept a passing re-test from a different area of the building as evidence that the failed area is now compliant.
For a full breakdown of the most common causes of Part E test failures, and how to prevent them, see the dedicated failures section in our Part E compliance guide.
Remediation options and what they cost
The right remediation depends on the size of the gap and what caused it, so it helps to think in three brackets.
Minor shortfall (1 to 3 dB): targeted interventions
Perimeter resealing with acoustic sealant at all wall, floor, and ceiling junctions is low cost, fast, and one of the first things to try on any failure, particularly where sealing was disturbed during finishing. Plasterboard seams should be taped and filled with acoustic sealant rather than standard filler. Back-to-back or adjacent sockets in the separating wall can be treated with acoustic back boxes or putty pads. Targeted sealing works can often be completed for a few hundred pounds per unit by the main contractor, depending on access.
Moderate shortfall (3 to 6 dB): additional mass or absorption
Bonding an additional layer of acoustic plasterboard (SoundBloc or similar) to the face of the separating wall or ceiling can add 2 to 4 dB of airborne performance, with finishes made good afterwards. For impact failures, a floating floor overlay (composite rubber mat plus chipboard) can improve impact performance by 5 to 10 dB without major structural work. It is worth noting that adding mass alone is not always the answer; the cause of the failure determines whether mass, sealing, or decoupling is the right lever. Expect several hundred to low thousands of pounds per unit for these interventions, depending on area, plus decoration. Our Part E soundproofing products guide covers the materials typically used.
Significant shortfall (6 dB or more): structural intervention
Where a floor and ceiling system has failed significantly, an independent ceiling mounted on resilient bars or mute clips, decoupled from the structure above, is the most effective intervention for both airborne and impact failures. It is also disruptive: the existing ceiling comes down, the new system goes in, and all finishes are made good. Where a separating wall has failed significantly, an independent stud lining decoupled from the existing wall, with acoustic mineral wool between studs and double SoundBloc, can add 10 to 15 dB in extreme cases. Independent ceiling systems in a finished flat are among the most expensive remediation routes, potentially running to several thousand pounds per unit once disruption, making good, and redecoration are included.
The general principle: remediation cost rises steeply with the severity of the failure and with how finished the building already is. Fixing acoustic issues during construction, before boarding up and final finishes, is always dramatically cheaper than working in a completed building. That is the whole case for early acoustic design advice, and NOVA’s free sound insulation design advice library exists to help developers get the specification right before anyone books a test.
How much does pre-completion sound testing cost?
Cost varies with the number and type of tests required, travel and mobilisation relative to the testing company’s base, how many sets can be completed in a single visit, and whether the testing company holds UKAS accreditation.
Some reliable relative points. A house test set (two airborne tests) is the simplest and least expensive option. A flat test set, with both floor and wall tests, is more involved and costs proportionally more. Multi-set visits, where several sets are completed in one day on the same development, are usually priced more efficiently than single visits. And re-tests attract a further charge on top of the original fee, plus the remediation cost itself, which is why getting it right first time is always the cheapest route.
On accreditation: UKAS-accredited testing may cost slightly more than non-accredited testing, because accreditation requires ongoing investment in quality systems, calibrated equipment, and audited processes. It is also increasingly required by building control, and it is the only appropriate choice where results need to be relied upon. A cheap test that building control queries or rejects is not cheap.
Set against the value of the development, testing is a small line item. Set against the cost of programme delay, remediation, and re-testing after a failure, good acoustic design and a reliable testing partner are easily justified.
For a competitive, no-obligation quote on pre-completion sound testing from a UKAS-accredited laboratory, contact your nearest NOVA Acoustics office. We respond within one business day.
Why choose NOVA Acoustics
Pre-completion sound testing is not a commodity. The quality of the methodology, the calibration of the equipment, and the experience of the tester all affect the reliability of the result. NOVA Acoustics carries UKAS accreditation specifically for sound insulation testing, which means every test we carry out is backed by an independently audited quality standard.
NOVA is one of a relatively small number of UKAS-accredited sound insulation testing laboratories in the UK (Accreditation No. 8568). Building control authorities increasingly require UKAS-accredited testing, and choosing an accredited tester from the outset removes the risk of results being queried or rejected.
Design and testing sit under one roof. NOVA provides both acoustic design advice and pre-completion testing, so the team that advises on the wall and floor specification can also test the completed building. That continuity reduces design-to-build translation errors, and it means NOVA has a direct interest in getting the design right in the first place. It is a large part of why our residential acoustic consultancy work and our testing work reinforce each other.
When tests fail, NOVA’s consultants can review the results, identify the likely cause, and advise on the most cost-effective remediation route. That advice draws on the failure patterns seen across hundreds of test visits rather than generic guidance.
Offices in Leeds, Manchester, London, Birmingham, Liverpool, Cambridge, Newcastle, Nottingham, Sheffield, Bristol, and Hull allow NOVA to deploy testing teams across England and Wales at competitive rates. For developments on tight completion programmes, fast mobilisation matters commercially.
And the design resource is free. NOVA publishes a comprehensive library of sound insulation design advice covering wall and floor systems for all major construction types. Developers who use it and commission NOVA for testing get continuity of acoustic approach from design through to verification.
Whether you need pre-completion sound testing, acoustic design advice, or support following a failed test, NOVA Acoustics is here to help. Get in touch.
Frequently asked questions
What is pre-completion sound testing?
Pre-completion sound testing is a site acoustic measurement carried out in a new or converted residential building before it is occupied, to demonstrate compliance with Part E of the Building Regulations. It measures airborne sound insulation (how well walls and floors resist airborne noise) and impact sound insulation (how well floors resist footstep noise). Results go to the local building control body as evidence that the building meets the required performance thresholds.
When does pre-completion sound testing need to happen?
Testing must be carried out when the building is substantially complete but not yet occupied. Partitions should be finished, floor finishes in place, and services installed. Testing too early, before finishes are complete, can produce misleadingly poor results and may not be accepted by building control.
What are the pass levels for a pre-completion sound test?
For new build residential development, the pass thresholds are DnT,w + Ctr ≥ 45 dB for airborne sound (walls and floors between dwellings) and L’nT,w ≤ 62 dB for impact sound (floors). For material change of use conversions, the thresholds are DnT,w + Ctr ≥ 43 dB and L’nT,w ≤ 64 dB. These are minimums; designing with a comfortable margin above them reduces the risk of failure on the day.
What happens if a pre-completion sound test fails?
Building control sign-off cannot be granted and the affected units cannot be occupied until the failed construction is remediated and a passing re-test is achieved. The first step is to review the results with an acoustic consultant to identify the cause. Remediation ranges from targeted perimeter resealing for marginal failures to independent ceiling or wall systems for significant ones. Remediation plus re-testing always costs more than correct specification in the first place.
Does every unit need to be sound tested?
Not necessarily. Part E allows sample testing, typically one set of tests per separating construction type per construction run. The sampling approach must be agreed with the building control body before testing commences. If a test fails, however, the failure is generally treated as applying to all units of that construction type, not just the tested one.
Does pre-completion testing need to be carried out by an accredited company?
Yes. Testing must be carried out by an accredited body, with UKAS or ANC accreditation required. Building control authorities in England increasingly specify UKAS accreditation. NOVA Acoustics holds UKAS accreditation (No. 8568) for sound insulation testing.
Can I avoid pre-completion sound testing altogether?
Yes, if the development uses a registered Robust Detail specification. Developments built to an approved Robust Detail are exempt from testing, provided the specification is registered before work starts and an RD inspector verifies the construction. Robust Details are generally not available for conversions or non-standard construction types, so for most smaller or bespoke projects, pre-completion testing remains the route.
How long does a pre-completion sound test take?
A standard flat test set (two impact and four airborne tests) typically takes 2 to 3 hours on site. A house set (two airborne tests) usually takes 1 to 2 hours. Multiple sets on the same day take proportionally longer, and the written report typically follows within a few working days of the visit.
Summary
Pre-completion sound testing is a mandatory requirement for most new residential development and conversions in England. It cannot be skipped, and it cannot be deferred until after occupation. The thresholds are fixed (DnT,w + Ctr ≥ 45 dB airborne and L’nT,w ≤ 62 dB impact for new builds; 43 dB and 64 dB for conversions), the testing must be accredited, and building control sign-off depends on the results.
A failed test is recoverable but expensive, and the cost rises with both the severity of the failure and how finished the building is. Prevention through correct acoustic design and workmanship is always the cheaper path, which is why the smart money engages acoustic advice early rather than treating the test as a formality at the end.
NOVA Acoustics is a UKAS-accredited testing laboratory (No. 8568) providing pre-completion sound insulation testing as well as acoustic design, with offices across England. That continuity, from specification through to verification, is the most reliable way to pass first time.
Get pre-completion sound testing from a UKAS-accredited laboratory, or get acoustic design advice to reduce the risk of failure before the test day arrives. Request a testing quote or browse our free sound insulation design advice.
Sources
- HM Government, The Building Regulations 2010, Approved Document E: Resistance to the Passage of Sound (2003 edition incorporating 2004, 2010, and 2015 amendments), including the performance standards for separating walls and floors: https://www.gov.uk/government/publications/resistance-to-sound-approved-document-e
- Robust Details Ltd, Robust Details scheme, plot registration, approved specifications, and site inspection requirements: https://www.robustdetails.com/
- United Kingdom Accreditation Service (UKAS), accreditation of sound insulation testing laboratories: https://www.ukas.com/
- Association of Noise Consultants (ANC), registration scheme for sound insulation testing: https://www.association-of-noise-consultants.co.uk/
- BSI, BS EN ISO 16283-1 and 16283-2: Acoustics – Field Measurement of Sound Insulation in Buildings and of Building Elements (airborne and impact sound measurement methods): https://www.bsigroup.com/
- NOVA Acoustics, UKAS Accredited Testing Laboratory No. 8568, sound insulation testing and acoustic design services: https://www.novaacoustics.co.uk/sound-testing/
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