Sound Insulation & Approved Document E

What is the Building Regulations Approved Document E?

The Building Regulations Approved Document E was released in 2003 and denoted the minimum requirements for the resistance to the passage of sound in residential dwellings. Specifically, the document stipulates the requirements for pre-completion sound insulation testing once the development's construction phase is complete. As well as the minimum required sound insulation for both airborne sound insulation and impact sound insulation.

What is airborne sound transmission and what is impact sound transmission?

Airborne sound transmission is airborne sound travelling through a partition wall or floor into the adjoining room or dwelling. Generally, airborne noise within a residential dwelling is produced by people speaking, music, the television and kitchen appliances.

Impact sound transmission occurs when an object or item impacts the separating floor and travels through the structure into the adjoining dwelling below. Generally, impact noise within a residential environment is generated by people walking/running on the floor or by items dropping or impacting the floor.

Approved Document E Sound Insulation Requirements and Criteria

Approved Document E sets out specific minimum standards for sound insulation between dwellings. The requirements are slightly different depending on what type of development is being constructed, for example, the newly constructed building criteria are slightly higher than that which is required in converted or refurbished buildings. Requirement E1 of the building regulations outlines the following requirements:

For new build Purpose Built Dwellings – House and Flats the airborne sound insulation requirement is 45 dB Dnt,w+ctr or above and the impact sound insulation requirement is 62 dB Lnt,w or below.

For Dwellings-Houses and Flats Formed by Material Change of Use, the criteria are relaxed by 2dB. For this type of development, the airborne sound insulation requirement is 43 dB Dnt,w+ctr or above. The impact sound insulation requirement is 64 dB Lnt,w or below.

How many sound insulation tests do I need?

In order to ensure that the development meets the minimum sound insulation requirements, Part E of the Building Regulations outlines the need for sound insulation testing upon completion of the development. The Regulations state that for larger developments only a sample of tests needs to be undertaken and not every wall or floor separating two dwellings. Generally, one set of tests would comprise of two airborne wall tests, two airborne floor tests and two impact floor tests. A sample of tests should be undertaken for each wall and floor construction type across the development. For example for a row of 10 terrace houses with the same wall construction on one set of two airborne sound insulation tests would be required. Within a block of flats containing 10 flats two airborne wall tests, two airborne floor tests and two impact floor tests would be required.

How are sound insulation tests undertaken?

Airborne sound insulation tests are undertaken by positioning a loudspeaker within one side of the dwelling playing a pink noise test signal. The pink noise is then measured within the source room with the speaker and within the receiving room on the other side of the partition floor or wall. The background sound level and level of reverberation within the receiving room are then measured. These noise levels are then used to calculate the sound reduction of the wall.

Impact sound insulation tests are undertaken by the use of an impact machine. The impact machine is a small machine with five hammers inside these hammers are connected to a mechanical system which raises and drops the hammers onto the floor from a standardised height. When the hammers strike the floor, the sound is transferred down into the adjoining dwelling. The resulting noise levels in the dwelling below are then measured in order to calculate the impact sound insulation value Lnt,w.

How do I pass a sound insulation test?

In order to pass a sound insulation test and achieve the building regulations criteria, the design of the floor or wall needs to be considered in detail.

The two main characteristics of a wall or floor that would pass an airborne sound insulation test would be a partition with high mass and effective decoupling. A prime example of this would be a concrete block cavity wall. The blockwork provides sufficient mass and the air cavity effectively eradicates the mechanical connection between both sides of the wall providing sufficient decoupling.

When considering impact sound transmission through a floor the best way to achieve the building regulations criteria is to apply a resilient layer or floating system effectively decoupling the floor and mitigating the impact noise at the source where the impact occurs on the floor surface.

If you are converting an existing building or building a new development it is always a good idea to get a specific sound insulation design undertaken if you are unsure of how to achieve the required standard of sound insulation.

What happens if I fail a sound insulation test?

The most common issue causing sound insulation test failures is a lack of initial acoustic design at the start of the project. It is essential that the resistance to the passage of sound is considered at the design stage or project inception, retrospectively resolving sound insulation failures once the project is complete can become very expensive and time-consuming.

If your sound insulation test fails upon completion the first step is to assess the current construction and the measured sound insulation test results. The sound insulation test engineer may be able to offer some indication as to how the test failed. An acoustic consultant should be able to easily guide you through the process of upgrading the wall or floor to the correct level using detail and cutting-edge sound insulation modelling and design. Once the wall or floor has been upgraded you will likely be required to undertake a further sound insulation test in order to get the Building Control officer to sign the property off.