Statutory Inspections · Mandatory · Completion

Acoustic Test Certificate (Building Regulations Part E)

The pre-completion sound insulation test certificate required for new residential buildings under Approved Document E. Tests airborne sound insulation (walls and floors between dwellings, minimum DnT,w + Ctr 45 dB) and impact sound insulation (floors, maximum L'nT,w 62 dB). Must be carried out by UKAS-accredited testing organisation. Failure requires remediation and retest before completion certificate.

Last reviewed: 2 April 2026 — This guide reflects UK law as of this date. Building Regulations 2010 — Approved Document E remains current with no amendments enacted as of 2 April 2026. Next scheduled review: 2 April 2027.

Document type	T10 — Acoustic Test Certificate (Part E)
Regulatory basis	Approved Document E (Resistance to the Passage of Sound), Building Regulations 2010
Testing standard	UKAS-accredited testing to BS EN ISO 16283 (field measurements of sound insulation)
Airborne requirement	D_nT,w + C_tr ≥ 45 dB for walls and floors between dwellings
Impact requirement	L'_nT,w ≤ 62 dB for floors between dwellings
Common failure causes	Flanking transmission, service penetrations, inadequate mass, poor junction detailing, air paths through separating elements

1. What Is an Acoustic Test Certificate?

An acoustic test certificate is the formal record of sound insulation testing carried out on separating walls and floors between dwellings, as required by Approved Document E of the Building Regulations. The purpose of testing is to demonstrate that the as-built construction achieves the minimum sound insulation performance standards set out in AD E, thereby protecting occupants from unreasonable noise transfer between dwellings. Testing must be carried out by a UKAS-accredited testing organisation using calibrated equipment and standardised test methods.

AD E sets two primary performance criteria for separating elements between dwellings. For airborne sound insulation, the standardised level difference D_nT,w + C_tr must be at least 45 dB. This measures the ability of the wall or floor to resist the passage of airborne sound — speech, music, television, and general living noise. For impact sound insulation (applicable to floors), the standardised impact sound pressure level L'_nT,wmust not exceed 62 dB. This measures how much impact noise — footsteps, dropped objects, furniture movement — is transmitted through the floor to the dwelling below.

Testing is carried out after the construction of the separating element is complete, including all finishes, but before the dwelling is occupied. The results are submitted to Building Control as evidence of compliance with Part E. If the separating element fails to meet the required performance standards, remedial work must be carried out and the element retested. Failure to achieve compliance can delay handover, trigger costly remedial works, and in the worst cases require partial demolition and reconstruction of the separating element.

Flanking transmission is the most common cause of acoustic test failure

Sound does not only travel directly through the separating wall or floor — it also travels around it, through flanking paths. These include junctions between the separating element and the external wall, internal walls, and floor/ceiling constructions. Service penetrations (pipes, cables, sockets, switches) that breach the separating element create direct air paths for sound transmission. Poor junction detailing, unfilled mortar joints, and gaps in cavity barriers are all common flanking paths. A separating wall or floor that achieves excellent direct sound insulation in laboratory conditions can still fail the field test if flanking paths are not properly addressed during construction. Designing and building for flanking performance, not just direct performance, is essential.

2. Key Content of the Acoustic Test Certificate

The acoustic test certificate must contain sufficient detail to demonstrate that the testing was carried out correctly, by a competent accredited organisation, using the correct methodology, and that the results are valid and traceable. The following table sets out the key content areas.

Section	Content required
Testing organisation	Name, address, and UKAS accreditation number of the testing organisation. The certificate must confirm that the testing was carried out within the scope of the organisation's UKAS accreditation for sound insulation field testing.
Project details	Project name, site address, developer/client name, Building Control body (local authority or approved inspector). Plot numbers or unit identifiers for the dwellings tested.
Test date(s)	Date(s) on which the sound insulation tests were carried out. Testing must be carried out after the separating element and all finishes are complete.
Building type	Type of building: new-build houses, new-build flats, conversion to flats, change of use. The applicable AD E performance standards may differ depending on building type (new build vs. conversion).
Separating elements tested	Description of each separating element tested: wall or floor, construction type (masonry, timber frame, steel frame, concrete), location (between which plots/units), orientation (party wall, separating floor). Drawing references where available.
Test results — Airborne (wall tests)	For each separating wall tested: measured D_nT,w + C_tr value in dB. Pass/fail against the AD E minimum of 45 dB. Frequency-dependent data (1/3 octave band results from 100 Hz to 3150 Hz). Reverberation time measurements in the receiving room.
Test results — Airborne (floor/ceiling tests)	For each separating floor tested for airborne sound: measured D_nT,w + C_tr value in dB. Pass/fail against the AD E minimum of 45 dB. Frequency-dependent data and reverberation time measurements.
Test results — Impact (floor tests)	For each separating floor tested for impact sound: measured L'_nT,w value in dB. Pass/fail against the AD E maximum of 62 dB. Frequency-dependent data (1/3 octave band results). The standardised tapping machine is used as the impact source.
Overall outcome	Overall pass or fail for each separating element. Summary of any elements that failed and require remedial work and retesting. Confirmation that all tested elements meet or exceed the AD E performance standards.
Tester	Name and qualifications of the individual who carried out the testing. Confirmation that the tester is competent and working within the UKAS-accredited scope of the testing organisation.
Submission to Building Control	Confirmation that the certificate has been (or will be) submitted to the relevant Building Control body as evidence of Part E compliance. Reference to any Building Control inspection or sign-off related to the acoustic testing.

Service penetrations are a critical failure point

Electrical sockets, switches, pipes, cables, and ventilation ducts that penetrate separating walls and floors create direct air paths for sound transmission. Back-to-back sockets on a separating wall are a particularly common cause of test failure. Sockets on opposite sides of a separating wall must be offset by at least 150 mm and the surrounding area fully sealed with acoustic sealant. All service penetrations must be fire-stopped and acoustically sealed. These details are often missed during first fix, and by the time acoustic testing takes place, remedial work to address penetrations can be difficult and costly.

3. Common Mistakes

Not designing for flanking transmission

Designing the separating wall or floor in isolation, without considering the flanking performance of the surrounding construction, is the most common cause of acoustic test failure. Sound travels around the separating element through junctions with external walls, internal walls, and floor/ceiling constructions. If the junction details do not include adequate flanking strips, cavity barriers, or acoustic breaks, the direct sound insulation of the separating element is bypassed. AD E provides guidance on flanking details, and Robust Details (where used) specify the required flanking treatments. These details must be designed in and built correctly — they cannot be retrofitted cost-effectively after the event.

Leaving insufficient programme time for acoustic testing

Acoustic testing requires the separating element and all finishes to be complete, but the dwelling must not yet be occupied. This creates a narrow window in the construction programme. Testing organisations typically require a minimum of 4 weeks' notice to schedule testing, and popular periods (approaching completion of large phases) can require longer lead times. Leaving acoustic testing to the last moment before handover, and then discovering a failure that requires remedial work and retesting, can delay practical completion by weeks. Book the testing organisation at least 4 weeks before the anticipated test date and build contingency into the programme for potential retesting.

4. Related Documents

Document	Relationship
B10 — RAMS: Brickwork and Blockwork	Masonry separating walls must be built to the specification in the acoustic design. Full mortar joints, correct bond pattern, and proper cavity fill are essential for achieving the required sound insulation. The brickwork RAMS should reference the acoustic specification.
B12 — RAMS: Plastering and Drylining	Plasterboard linings, independent wall linings, and ceiling treatments are critical components of acoustic performance. The plastering and drylining RAMS must specify the correct board type, thickness, fixing method, and junction details as set out in the acoustic design.
B9 — RAMS: Mechanical and Plumbing	Service penetrations through separating elements must be minimised, offset, and acoustically sealed. The M&E RAMS should specify acoustic requirements for pipe runs, duct penetrations, and socket positions on separating walls and floors.
B6 — RAMS: Electrical Installation	Electrical sockets, switches, and cable routes through separating walls and floors must comply with acoustic detailing requirements. Back-to-back sockets must be avoided. All penetrations must be sealed.

5. Frequently Asked Questions

Can Robust Details be used instead of pre-completion testing?▾

Yes. Robust Details Ltd operates a scheme of pre-approved wall and floor constructions that have been demonstrated to consistently achieve the AD E performance standards without the need for pre-completion testing. If a developer registers with Robust Details and builds the separating elements using an approved Robust Detail construction (following all the specified materials, methods, and junction details exactly), pre-completion sound insulation testing is waived. However, this relies on the construction being built precisely to the Robust Detail specification — any deviation (wrong board type, missing flanking strip, substituted insulation) invalidates the exemption, and testing would then be required. Robust Details carries out its own compliance inspections to verify that registered plots are built correctly.

How many separating elements need to be tested?▾

AD E requires a representative sample of separating elements to be tested. The sampling rate is typically one set of tests for every ten dwellings of each construction type. For example, on a development of 40 houses with identical party wall construction, four sets of party wall tests would be required. Where there are different construction types (e.g. masonry party walls and timber-frame separating floors), each type must be sampled separately. Building Control may require additional testing if early results are marginal or if construction quality concerns are identified during inspections.

What happens if a separating element fails the acoustic test?▾

If a separating element fails to meet the AD E performance standard, the developer must carry out remedial work to improve the sound insulation and then arrange retesting. Common remedial measures include adding an independent plasterboard lining to a separating wall, installing a resilient bar ceiling system below a separating floor, sealing air paths at junctions and service penetrations, and adding a floating floor treatment. The remedial work must address the specific cause of failure — which is why the frequency-dependent test data is important, as it helps identify whether the failure is caused by a mass deficiency, an air path, or a flanking issue. Building Control will not sign off Part E compliance until a passing test result is achieved.

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