Pre-Completion Sound Testing: What It Is, When You Need It and How It Works

Pre-completion sound testing checks how well sound is controlled between adjoining homes or rooms used for residential purposes.

The testing is normally carried out when the building is essentially complete but before it is occupied. It provides evidence to the building control body that the separating walls and floors achieve the sound-insulation performance required by Part E of the Building Regulations.

Tests may be needed for new-build houses and flats, residential conversions, hotels, halls of residence and other types of residential accommodation.

However, testing is not required for every residential project, and the number of tests depends on the development’s layout and construction.

This guide explains when pre-completion testing applies, how the tests are carried out and what happens if a construction fails.

What is pre-completion sound testing?

Pre-completion sound testing is an on-site assessment of the sound insulation between adjoining properties or residential rooms.

It is used to assess Requirement E1 of the Building Regulations in England, which requires dwelling-houses, flats and rooms for residential purposes to provide reasonable resistance to sound from adjoining buildings and other parts of the same building.

The testing concentrates on separating elements, such as:

• A party wall between adjoining houses
• A wall between separate flats
• A floor between one flat and another
• A floor or wall between hotel bedrooms
• Separating constructions in student accommodation
• Separating walls and floors in a building converted into homes

It does not normally test ordinary internal walls within one home or sound entering through the external façade.

Does this guide apply throughout the UK?

This article refers specifically to Approved Document E and the Building Regulations in England.

Wales, Scotland and Northern Ireland have their own regulations, technical guidance and testing arrangements. A development outside England should be assessed against the requirements that apply in that nation.

Which buildings need pre-completion sound testing?

Approved Document E provides for testing of:

• Purpose-built dwelling-houses and flats
• Dwelling-houses and flats formed through a material change of use
• Purpose-built rooms for residential purposes
• Rooms for residential purposes formed through a material change of use

A room for residential purposes is a room or suite of rooms used by one or more people to live and sleep in, where it is not itself a dwelling-house or flat.

The definition includes rooms in:

• Hotels
• Hostels
• Boarding houses
• Halls of residence
• Residential homes

It does not include patient accommodation in hospitals or similar establishments.

Whether a particular care, supported-living or communal accommodation project falls within the definition should be confirmed with the project’s building control body.

Is testing required for every new home?

No.

A detached house with no separating wall or floor adjoining another property will not normally need a pre-completion sound-insulation test.

Testing may also be avoided on some purpose-built attached houses and flats where the developer correctly uses the Robust Details scheme.

Robust Details provides approved separating wall and floor constructions that can be used as an alternative to routine pre-completion testing for new adjoining dwellings. The plots must be registered and constructed in accordance with the relevant specification. The scheme does not generally apply to conversions, extensions or refurbishments.

The testing or Robust Details route should be agreed before construction progresses too far.

What is the difference between Part E and Approved Document E?

Part E contains the legal requirements relating to resistance to sound.

Approved Document E provides practical guidance on ways of meeting those requirements.

Following an Approved Document is not the only possible route to compliance, but its recommendations are commonly used by designers, contractors, testers and building control bodies.

When should pre-completion testing take place?

Testing should be carried out once the rooms on both sides of the separating wall or floor are essentially complete, except for decoration.

This means the constructions being tested and their associated flanking elements should be in their finished condition.

Approved Document E also says impact sound-insulation testing should be completed without a soft floor covering, such as carpet or foam-backed vinyl, installed over the floor.

The original article’s suggestion that testing takes place without “floor installations” is therefore misleading. The floor construction and acoustic treatments must be complete. It is normally only removable soft finishes that need to be absent for the impact test.

The tester should be consulted before the visit to confirm the precise site-readiness requirements.

Why does the building need to be nearly complete?

Sound can travel through more than the main wall or floor.

It may also pass through:

• External walls
• Internal walls
• Floor slabs
• Ceiling voids
• Roof spaces
• Façade systems
• Service penetrations
• Structural junctions

These alternative routes are known as flanking transmission.

Testing before these elements are complete may not represent the final building. Equally, testing after the property has been occupied can make access and remedial work much more difficult.

What are airborne and impact sound tests?

Pre-completion testing uses two main types of test.

Airborne sound-insulation testing

Airborne sound includes:

• Speech
• Television
• Music
• Everyday domestic activity

During an airborne test, a loudspeaker produces controlled noise in the source room.

The tester measures the sound in:

• The source room
• The adjoining receiving room

Background sound and the receiving room’s reverberation time are also measured.

These results are used to determine the standardised airborne sound-insulation performance of the separating wall or floor.

The current field measurement standard for airborne sound insulation is BS EN ISO 16283-1:2014+A1:2017, with results rated under BS EN ISO 717-1:2020.

Impact sound-insulation testing

Impact sound is created by physical contact with a floor or stair, such as:

• Footsteps
• Objects being dropped
• Furniture being moved

For an impact test, a standard tapping machine is placed on the floor in the property above.

The machine contains a series of hammers that repeatedly strike the floor in a controlled and repeatable way. Sound levels are then measured in the room below.

The current field measurement standard for impact sound insulation is BS EN ISO 16283-2:2020, with results rated under BS EN ISO 717-2:2020.

What do the results mean?

Approved Document E uses two main single-number ratings.

DnT,w + Ctr

This is the rating used for airborne sound insulation between completed rooms.

A higher result is better because it indicates that the separating construction is reducing more airborne sound.

L’nT,w

This is the rating used for impact sound insulation through a completed floor or stair.

A lower result is better because it indicates that less impact sound is reaching the room below.

These figures should not be confused with laboratory product ratings such as Rw.

What are the Part E sound-insulation targets?

For purpose-built dwelling-houses and flats, the minimum airborne sound-insulation performance is:

• Walls: DnT,w + Ctr of at least 45 dB
• Floors and separating stairs: DnT,w + Ctr of at least 45 dB

The maximum impact sound level for separating floors and stairs is:

• L’nT,w of no more than 62 dB

For dwelling-houses and flats created through a material change of use, the targets are:

• Airborne: DnT,w + Ctr of at least 43 dB
• Impact: L’nT,w of no more than 64 dB

Rooms for residential purposes have slightly different targets.

For purpose-built rooms for residential purposes:

• Separating walls: at least 43 dB
• Separating floors and stairs: at least 45 dB
• Impact sound through floors and stairs: no more than 62 dB

For rooms formed through a material change of use:

• Airborne sound insulation: at least 43 dB
• Impact sound: no more than 64 dB

A result that misses the required value by any margin is recorded as a failure. The figures include an allowance for measurement uncertainty.

How many sound tests are required?

The often-used statement that “10% of the development must be tested” is only a simplified summary.

Approved Document E groups properties according to factors such as:

• Whether they are houses, flats or rooms for residential purposes
• The type of separating wall
• The type of separating floor
• Flanking constructions
• Room layouts
• Significant construction differences

Different construction types may need separate sub-groups.

The normal programme is:

1. Test the first properties ready for completion or sale in each group or sub-group.
2. Assuming there are no failures, carry out at least one further set of tests for every ten properties in that group or sub-group.
3. On larger developments, spread testing across a substantial part of the construction period rather than leaving it all until the end.

This means a small project containing only one pair of adjoining houses or flats may still need a set of tests.

What is included in a set of tests?

The number of individual tests depends on the property arrangement.

Adjoining houses

A normal set consists of two airborne sound-insulation tests through the separating wall:

• One test between a pair of suitable living rooms
• One test between a separate pair of suitable bedrooms

Flats with a separating floor but no separating wall

A normal set consists of:

• Two airborne sound-insulation tests through the separating floor
• Two impact sound-insulation tests through the separating floor

Flats with both a separating floor and wall

A normal set consists of:

• Two airborne tests through the separating wall
• Two airborne tests through the separating floor
• Two impact tests through the separating floor

Access to at least three flats will normally be needed to complete the full set.

Rooms for residential purposes

The same general principles apply, but the programme may need to be adapted to the building’s particular layout and use.

The final test sample should always be agreed with the building control body.

Who chooses the properties to be tested?

The building control body is responsible for determining which properties should be selected for testing.

Developers should discuss:

• Construction groups
• Property layouts
• Completion dates
• The proposed testing programme
• The first units becoming available
• Any unusual or potentially unfavourable constructions

Properties should not be selected purely because they appear most likely to pass.

Approved Document E specifically recognises that properties with less favourable features may need to form their own sub-group.

Who can carry out Part E testing?

Testing should be completed by a test body with suitable third-party accreditation.

Approved Document E recognises:

• UKAS-accredited test bodies
• Members of the ANC Registration Scheme for Sound Insulation Testing

The ANC scheme provides qualified testers, a tracked reporting process and verification information that building control bodies can check through its ADvANCE system.

The tester should be appointed early enough to:

• Review the proposed sample
• Confirm site readiness
• Coordinate access
• Highlight obvious risks
• Arrange the test around the completion programme

What happens during the visit?

The exact process depends on the building, but the tester will normally:

1. Confirm the rooms and separating elements being tested.
2. Check that the rooms are suitable and sufficiently complete.
3. Set up the loudspeaker and measurement equipment.
4. Carry out source-room and receiving-room measurements.
5. Measure background sound and reverberation where required.
6. Use a tapping machine for impact tests.
7. Calculate and review the results.
8. Prepare the test report.

Testing requires access to the rooms on both sides of each separating construction.

The site also needs to be quiet enough for reliable measurements. Excessive construction noise or restricted access can prevent the planned tests from being completed.

What information appears in the report?

Approved Document E requires the report to identify matters including:

• The building address
• The property type
• The date of testing
• The test organisation
• Its third-party accreditation details
• The tester
• The rooms used
• The measured results
• The required performance
• A pass or fail result for each test

The report is provided to the relevant building control body.

ANC-registered tests also receive verification information that enables building control to check the test through the scheme. This is not the same as publishing the full results publicly online.

What happens if a sound test fails?

If any individual airborne or impact test does not achieve the required value, the set of tests fails.

The next steps may include:

• Investigating the cause
• Carrying out remedial work
• Repeating the failed test
• Testing additional rooms
• Reviewing similar properties
• Increasing the rate of testing

A failure raises questions about other properties sharing the same wall, floor, construction or flanking details.

The developer may need to demonstrate that these other areas comply, either through additional testing, remedial work or evidence that the cause is isolated to the tested property.

What commonly causes a sound-test failure?

Possible causes include:

• Gaps or cracks in separating constructions
• Poorly sealed wall edges
• Unsealed service penetrations
• Back-to-back electrical sockets
• Missing layers of board
• Incorrect insulation within cavities
• Rigid connections across isolated constructions
• Bridged resilient floor layers
• Poorly installed floating floors
• Partitions stopping at a suspended ceiling
• Continuous ceiling or floor voids
• Incorrect product substitutions
• Weak junctions with external walls
• Flanking transmission through the structure

The cause is not always visible from within the tested room.

The tester or acoustic consultant may need to review drawings, inspect details or carry out further diagnostic testing.

How can developers reduce the risk of failure?

The most reliable approach is to consider sound insulation during design and construction rather than relying on the final test to identify problems.

Useful steps include:

• Set clear acoustic performance requirements
• Review wall and floor constructions before work starts
• Consider flanking transmission at junctions
• Coordinate service penetrations
• Review product substitutions
• Inspect acoustic details before they are concealed
• Protect resilient layers during following trades
• Test the first completed units early
• Investigate marginal results rather than assuming later units will pass

Approved Document E recommends testing more frequently towards the beginning of a development so potential problems can be identified early.

Can an acoustic consultant guarantee a pass?

No.

A consultant can review the design, assess risks, inspect construction and recommend improvements, but the final result depends on the completed building.

Performance may be affected by:

• Workmanship
• Product substitutions
• Site changes
• Hidden gaps
• Junction details
• Damage by later trades
• The actual construction compared with the drawings

Claims that early advice will “ensure” or “guarantee” a pass should therefore be avoided.

The better aim is to reduce the risk of failure and identify potential weaknesses before completion.

Is pre-completion testing the same as BREEAM acoustic testing?

Not necessarily.

Pre-completion testing under Approved Document E concerns the sound insulation of relevant separating walls and floors in dwellings and rooms for residential purposes.

A BREEAM assessment may require other acoustic measurements, depending on:

• The scheme
• Building type
• Credit being targeted
• Room use
• Project criteria

These may include:

• Internal ambient noise
• Reverberation time
• Sound insulation between rooms
• Building-services noise

The ANC Registration Scheme route only applies to the building and room types within its recognised scope. Other BREEAM testing may need to be completed through a different suitably qualified route.

Does Part E testing apply to schools and hospitals?

Schools are covered by Requirement E4 and associated school acoustic guidance, rather than the normal pre-completion testing programme for houses and flats.

Hospital patient rooms are specifically excluded from the Building Regulations definition of a room for residential purposes. They may still require acoustic design and testing under the project brief or healthcare guidance, but this is not the same as Part E pre-completion testing.

Why involve an acoustic consultant before completion?

Pre-completion testing confirms the performance of the finished construction. By that stage, some weaknesses may already be hidden behind walls, ceilings and finishes.

Earlier acoustic support can include:

• Reviewing proposed wall and floor types
• Assessing flanking paths
• Reviewing junction details
• Commenting on doors and penetrations
• Inspecting work during construction
• Reviewing substitutions
• Planning the testing sample
• Advising after a failed test

This helps make testing part of a wider acoustic quality process rather than a final administrative hurdle.

Talk to auricl about pre-completion sound testing

If your development needs Part E testing, it is worth planning the programme before the first units are finished.

Tell us about the building type, number of properties, separating constructions and expected completion dates. We can review the likely requirements, arrange the appropriate testing and explain the results clearly.