Solutions for Part E Building Regs

Understanding the new Part E Building Regulations
Custom Audio Designs Ltd offers Sound Testing. Call 01730 269572 for details.

The results of unwanted noise – from mild irritation to severe stress – have a detrimental effect on people’s health and their quality of life.

This is particularly bad in homes and apartment blocks where the scale of noise has increased dramatically in recent years to become one of the 21st century’s biggest environmental and building problems. At a time when the construction industry is being encouraged to build to greater housing densities, this issue is even more significant.

To combat the current noise pollution problems the Government has introduced new legislation. These new standards have been published in the new Approved Document – Part E (England and Wales) of the Building Regulations ‘Resistance to the passage of Sound’, which came into effect on 21st January 2004 for new build and 1st July 2003 for refurbishment.

The Government is tackling the problem by introducing more robust building standards to improve soundproofing in new homes and schools – both new build and refurbishment projects – in England and Wales (Part E).

The aims of the Part E legislation are to:

• improve acoustics and therefore sound privacy between residential dwellings
• improve the sound reduction of internal walls and floors within the home
• improve the sound reduction between rooms and in common areas in hostels, hotels, residential homes, schools, hospitals, etc.
• re-address sound performance criteria, taking into consideration modern day low frequency sounds such as TVs, stereos, etc. (considered to be the main offenders in the majority of the 180,000 complaints about noise received each year by local authorities).
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The table below summarises the acoustic regulations as published in Part E 2003 Building Regulations ‘Resistance to the Passage of Sound’:

Element of Construction (Internal walls that include a door are exempt from this requirement)	Minimum airborne sound transmission (site test result) DnT,w + Ctr dB	Maximum impact sound transmission (site rest result) L’nT,w dB	Minimum airborne sound transmission (lab test result) Rw dB
Separating walls between dwellings	45
Separating walls between rooms used for residential purposes	43
Separating walls between rooms created by a change of use	43
Separating floors between dwellings and rooms used for residential purposes	45	62
Separating floors between rooms created by a change of use	43	64
An internal wall or floor between a bathroom/WC and a habitable room. Also between bedrooms and between bedrooms and any other room in the dwelling.			40

Pre-Completion Testing

For the first time, pre-completion testing is being enforced to ensure that buildings meet the Part E standards.

The only exception to the regulation is where the building conforms to a Robust Standard Detail (RSD) document, which contains details of those constructions that perform consistently well and do not require on-site testing.

The Regulations state that one in ten of each construction type requires testing (selected at the Building Inspector’s discretion). If a failure occurs, then the construction will need to be improved and re-tested.

Each building environment is unique and there are many variables that can impact on the acoustic performance, such as workmanship, services, existing structure and other external factors.

Therefore specifiers should be mindful of these issues when selecting an acoustic construction type and it is worth noting that small defects in the build can significantly affect the overall acoustic performance.

REMEMBER an acoustic construction will only ever be as good as its weakest link.

DEFINITION OF TERMS

Term	Definition		Term	Definition
Ctr	The correction factor to a sound insulation quantity to take into account low frequency noise		Internal wall	Any wall that does not have a separating function
Decibel (dB)	The unit used for many acoustic quantities to indicate the level with respect to a reference level		L’nT	The impact sound pressure level in a stated frequency band, corrected for the reverberation time. See BS EN ISO 140-7: 1998
DnT	The difference in sound level between a pair of rooms, in a stated frequency band, corrected for the reverberation time. See BS EN ISO 140-4: 1998		L’nT,w	A single-number quantity used to characterise the impact sound insulation of floors. See BS EN ISO 717-2: 1997
DnT,w	A single-number quantity which characterises the airborne sound insulation between rooms. See BS EN ISO 717-1: 1997		Noise	Unwanted sound
DnT,w + Ctr	A single-number quantity which characterises the airborne sound insulation between rooms using noise spectrum no. 2, as defined in BS EN ISO 717-1: 1997		Pre-completion testing (PCT)	A new requirement to Part E where structures not conforming to the RSD will be tested prior to completion to check they reach the required standards.
Flanking transmission	Sound transmitted through rooms via flanking elements (an indirect path) instead of directly through separating elements (e.g. the top or bottom of a separating wall)		Robust Standard Detail (RSD)	A collection of pre-approved constructions that, if used, negate the need for PCT.
Frequency	The number of pressure variations (or cycles) per second that gives sound its distinctive tone. The unit of frequency is the Hertz (Hz)		Rw	The measurement used to rate the sound insulation of a material or building element in a laboratory
Hertz (Hz)	The unit of the frequency of the sound		Separating Floor	Floor that separates rooms or flats for residential purposes
Impact sound	Sound resulting from direct impact on a building element, i.e. walking, jumping		Separating wall	Wall that separates adjoining dwellings, houses, flats or rooms
Internal floor	Any floor that is not a separating floor		Sound Reduction Index (SRI)	A quantity measured in a laboratory that characterises the sound insulation properties of a material or building element in a stated frequency band.

Additional helpful information

Flanking Noise

When attempting to make any sort of construction compliant to the Part E Regulations it is important to note that sound does not always go straight through a building element. If the wall/floor/partition concerned is well acoustically insulated, then sound will simply go up and over or around the sides. This is called ‘flanking transmission’ and it occurs when sound travels along elements shared by adjacent structures.

If flanking constructions are not correctly specified or constructed, flanking transmission can exceed direct transmission and seriously reduce the overall capabilities of the construction. The best way to deal with this issue is to use resilient neoprene-type ‘flanking’ strips at the top and bottom of every wall and around the edges of floors as well as using an acoustic sealant wherever possible.

Ctr Adjusting Factor

The +Ctr factor varies according to the construction and can result in the original R_w dB value being reduced by up to 13dB. This impact on resulting solutions is critical in meeting the required Standards:

• 49RwdB with a + Ctr of -10: would not meet the required standard; and
• 50RwdB +Ctr: This shows that the correction factor has been taken into account.

Workmanship

To ensure maximum performance from a soundproof structure, it is vital that great care is taken in its construction. It must be built as if it needed to be waterproof, since sound, like water, light and air, will find the smallest crack or hole and expose it as a structural weakness.

Any hole or gap will significantly reduce acoustic performance. A single 25mm hole can reduce performance by up to a massive 15dB which may render the structure acoustically useless.

Although a 25mm hole would be visible, a crack 1mm x 1m will not always be obvious, and if not treated with an acoustic sealant it will be extremely detrimental to the acoustic performance.

Installation tips

• Stagger all the joints when double layering plasterboard or any other soundproofing material.
• Always ensure soundproofing goes all the way to the floor and all the way up to the top, even behind a skirting or cornice .
• For optimum performance, use proper acoustic sealant on all the joints and any cracks or holes.
• DO NOT place light or plug sockets back to back otherwise the sound will go straight through the structure.

The acoustic performance of any tested acoustic structure may vary on site so it is always advisable to choose a solution that exceeds the acoustic requirement (by around 10dB) to limit the potential impact of any site variances.