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. In this short guide, we outline the basics of building regulations part-E – sound, and what it takes to achieve compliance.

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 related to airborne sound only. The lower the value, the better. It does not apply to walls within the same dwelling.

LnT,w dB is the weighted standardized impact sound between two spaces. Higher values mean more impact sound in being transmitted; lower values indicate better results. Impact sound is only relevant for apartment or duplex units, it does not apply to floors within the same dwelling.

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 Units Ought to be Tested?

It depends on the construction type of separating elements. 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.


How to Achieve an Acceptable Acoustic Design

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.