Residential Acoustics – BCAR Part-E

Quick Reference Guide

Part-E of the Building Regulations deals with sound in dwellings. Its aim is to ensure that dwellings achieve a reasonable degree of sound insulation from adjoining buildings, or separate dwellings within the same unit. It therefore sets residential acoustics performance standards for party walls and floors separating dwellings.

Residential acoustics services at Dolphin House , Dublin 8

Performance requirements for residential acoustics:

Regulation E1 sets the following standards:

Performance Requirements

Separating construction

Airborne sound insulation DnT,w dB

Impact sound insulation LnT,w dB


53 (min)


53 (min)

58 (max)


What do these numbers mean?

DnT,w dB is the weighted standardized level difference between two dwellings. In other words, it is the minimum on-site performance that ought to be achieved by a separating wall or floor, and it is related to airborne sound only. The higher the value, the better.

LnT,w dB is the weighted standardized impact sound between two spaces. Higher values mean more impact sound in being transmitted; therefore, lower values indicate better results. Impact sound is only relevant for apartment or duplex units. Impact sound is only relevant to floors. 

The fact that higher DnT,w values means better performance, but higher LnT,w values means poorer performance is confusing. One way to remember this is to think of the D in DnT,w as the level DIFFERENCE, and the L in LnT,w as the Level…a higher level DIFFERENCE means better sound separation, whereas a high LEVEL means more sound is coming through. 


What is meant by ‘Separating Construction’?

A separating construction is a wall or floor which separates different dwellings. Walls and floors within the same dwelling do not have a specific acoustic requirement under Part-E; it is up to the client/developer whether or not they wish to improve the indoor acoustic quality of the dwellings by setting standards for internal separating elements. 

What happens if we fail a test?

A failed test means that the performance values outlined in Regulation E1 has not been met. Put simply, remedial works must be carried out on affected areas and re-tested to ensure that compliance is achieved. 

How many ‘Separating Constructions’ need to be tested to show compliance?

It depends on the construction type of separating elements. If the separating elements have been designed and constructed as per the guidance offered in TGD Part-E Sound,  the frequency of testing (i.e. the number of walls/floors that need to be tested) is lower. ‘Other constructions’ which have been verified by a qualified acoustic consultant are generally acceptable, however the testing frequency will be higher.

The following frequency of testing can be expected:

Number of attached dwellings ‘Sets of Tests’ required
First 8 dwellings (or part thereof) planned for completion. At Least one ‘Set of test’ for each separating element up to 4 No. ‘sets of tests’.
Greater than 8 but less than or equal to 20 At least 6 (in total).
Greater than 20 but less than or equal to 40 At least 6 + 10% x No. of attached dwellings greater than 20.
Greater than 40 but less than or equal to 100 At least 8 + 5% x No. of attached dwellings greater than 40.
More than 100 At least 11 + 5% x No. of attached dwellings greater than 100.

Note: a ‘Set of Tests’ comprises of at least two airborne tests for dwelling houses (e.g. upstairs bedroom-bedroom, and downstaris kitchen-kitchen), and six individual tests for apartment/duplex units to include two airborne wall-wall tests, two airbore floor-floor tests and two impact sound tests to the unit below. 

How to meet acceptable standards for residential buildings. . 

TGD Part-E Sound offers a number of standard details which, if constructed correctly, will be expected to achieve compliance with building regulation E1. iAcoustics offers computer simulations of any proposed separating construction detail to assess the likely sound insulation performance of that element when built on-site. 

Part-E does not set performance standards for noise break-in through the building envelope, building services noise or vibration control, however it does require that these elements are considered appropriately by means of acoustic assessment. Expert acoustic advise should be sought in these cases to ensure that acceptable levels of background noise is maintained within internal spaces. 

Who should carry out the acoustic testing?

TGD Part-E requires that all testing personnel are competent in the measurement of sound insulation in buildings and possess sufficient knowledge, training and experience appropriate to the nature of the work he/she is to carry out. Acoustic testing is a complex task and should be undertaken by Acoustic Consultants