Posts Tagged ‘Building Regulations’

Why aren’t we all enjoying a quiet night’s sleep?

31/07/2012

The introduction of Building Regulations Part E in July 2003 represented a big step by which all residential developments in England and Wales had to undergo pre-completion acoustic tests and meet certain airborne and impact sound performance figures. In 2004, building to Robust Details was added to this, providing an alternative method to pre-completion testing to show compliance with the Part E of the Building Regulations. So – nine years on, is everything as quiet as a mouse?

Patrick Dent, AMIOA MEng and Technical Director of Total Vibration Solutions Ltd, explores the issue of noise.

Image by Romana Klee on Flickr

Have these regulations meant that all new build dwellings and those formed from a material change of use are being constructed in a way that provides no noise issues and leaves each and every resident as happy as the proverbial Larry? Well, the simple answer is no. My weeks rarely go by without speaking to an individual who is having noise issues within their newly constructed apartment or house, yet when we investigate their complaint we find that the development met the requirements of Approved Document Part E of the Building Regulations.

So what’s going wrong? Do we need to revise Part E of the building regs? Are we overlooking certain things in the testing? Or do the regulations simply not give a result that the end client deems acceptable?

In truth, there are a wide variety of reasons why we are still encountering noise problems. One factor that caused a great deal of issues originally – although a lot of developers and specifiers are now aware of this trait of certain materials – was the problem of creep. Acoustic underlays and under-screed materials, which offered good acoustic performance initially, would continue to deflect under load over time and not recover to their original thickness. This would result in the resilience in the floor being lost, floors dropping, and floors that met the pre-completion testing initially, suddenly failing six months later.

This is quite an easily rectified problem that can be overcome by developers and specifiers ensuring that they do not use materials that are susceptible to creep. Foams are particularly prone to creep, so any foams used in this capacity should be closed-cell and cross-linked, however any reputable manufacturer or supplier should have test data available on the creep performance of their materials.

The more complex problems come when we investigate noise complaints where there clearly is a noise problem, and yet the development still passes the impact and airborne tests required to comply with Part E of the Building Regulations.

One such example I was made aware of recently involved some luxury apartments where the occupants had got together and complained that the sound insulation in the floors of their apartments were not good enough. An acoustic consultant was called in to independently test the floors. The results gave on average an airborne DnT,w+Ctr of 50dB (Part E requires a minimum of 45dB for new builds and 43dB for dwellings formed by material change of use, which the apartments actually were in this case) and an impact figure LnT,w of 52dB (Part E requires a maximum of 62dB for new builds and 64dB for material change of use). In other words, figures that any developers would be very happy with, and that were comfortably within the requirements of the building regulations.

However, what the acoustician did notice was the incredibly low background noise level. So although the noise levels caused by people walking above wouldn’t be noticed within a building with a more “normal” level of background noise, in these luxury flats, such dramatic but inconstant changes in noise level makes the sound very audible and quite disturbing.

A lack of background noise makes occasional sounds all the more noticeable

This brings us to the fact that an individual’s threshold of hearing and their perception of noise will change depending upon the environment that they are in. Part E of the Building Regulations doesn’t take the background noise level into account – so in this case, the occupants of these luxury flats are left feeling aggrieved at what they perceive as poor sound insulation in their building, whilst the builders would point to the testing that shows they have more than exceeded the requirements. So who is at fault?

Problems with background noise levels aren’t the only issues that we see on a regular basis. There is a widely accepted agreement that the tapping machine used in ISO 140 does not provide an accurate reproduction of the noise produced by footfall. Similarly, the test does not consider the low frequency performance and given that what you are hearing – particularly in dwellings formed by material change of use with timber floors – is caused by the deflection of the joists induced by the footfall, which produces sound at much lower frequencies than 100Hz, the ISO 140 calculation methods ignore it.

AcoustiCORK™ agglomerated cork underlay for impact noise and thermal insulation

So does this mean that the tests are useless and we should completely overturn them? Well, the simple answer is no. In the majority of cases, Part E provides a very good standard to ensure that the end occupant is not disturbed by noise. But here is where we need to be careful. It is a standard. It is the minimum requirements that a building needs to achieve. Certain circumstances, such as a low background noise level, a higher degree of luxury etc., will dictate that the builder needs to achieve a far greater level of sound insulation.

You wouldn’t fit out the furniture of a student hall of residence in the same way you would million pound apartments. Neither should you treat the sound insulation in the same way.

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