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Time for a soundcheck

technical & practice

The new Approved Document E comes into force on 1 July.

Here we look at the implications of the new regulations The new Approved Document E (ADE), 'Resistance to the Passage of Sound', has been launched and is downloadable from the Office of the Deputy Prime Minister's (ODPM) website at www. safety. odpm. gov. uk/ bregs/approvede/pdf/approvede. pdf

It is effectively a complete reworking of its predecessor (Part E: 1992 edition) which runs out on 1 July 2003, and at 76 pages is twice the size.

ADE deals with sound transmission generally, identifying flanking transmission and reverberation and naturalising the information on airborne and impact sound which comprised the limits of the previous guidance. The new regulations also include a new section on acoustic conditions in schools (albeit only a paragraph, ominously cross-referenced to yet another 'to be published' DfES Bulletin 93 'The Acoustic Design of Schools'). This adds a nondomestic element to the regulations, paving the way for the incorporation of other specific public sector acoustic memoranda (hospitals, health centres, laboratories, etc) into future amendments. ADE: 2003 also applies to flats, hostels and hotel accommodation.

Sound standards

The regulations begin with a new Section 0 that prioritises a decibel reduction performance specification over the constructional and density requirements of the previous edition.

In Clause 0.6, it is recognised that improving the sound insulation of historic buildings may result in detrimental visual intrusion, in which case, 'it will be reasonable to improve the sound insulation as much as is practical, and to affix a notice showing sound insulation value(s) in a conspicuous place inside the building.'

ADE: 2003 goes into more detail than its predecessor and takes account of construction leakages which had not previously been factored in. The method of determining the mass of a particular wall type has been expanded to include the effects of wall ties, mortar joints, brick frogs and voids, although fewer graphic examples are given. All examples replicate the requirements in the 1992 edition, although there appears to be a change in the density of large concrete panels, previously listed at 1,500Kg/m 2, documented in the new edition as a composite figure. A great deal of extra information has been added to usefully detail junctions and closers. Also, there is a regular 'dos' and 'don'ts' box containing handy titbits such as: 'Do stagger the position of sockets on opposite sides of a separating wall'; and, 'Do not build cavity walls off continuous solid concrete slab floor.'

Pre-completion testing is a new requirement (see box). To carry out pre-completion testing, residential buildings should be broken down into sub-groups, to enable a thorough evaluation of sound transfer between properties. Tests will normally include four airborne tests and two impact tests at different locations in the sub-group, and ADE: 2003 sets out suggested locations.

In Section 7, detailing the permissible reverberation in common internal rooms, once again, what might at first appear to be a straightforward section has been complicated by overworked examples. As a rule of thumb, soffits (of stairs and corridors) should be covered with absorptive material Class C. However, where large areas are involved (and hence small areas of material saved result in large savings), an alternative method of calculation incorporates relaxations to take into account the absorptive coefficients of floor and wall finishes and fixtures and fittings.

Robust details

At the briefing launch before Christmas, the ODPM officers charged with overseeing the issue of sound insulation sheepishly confirmed that the Robust Standard Details (RSDs) will not be harmonised with Approved Document Part L's RSDs.

'It's a dilemma, ' the spokesman said. 'In general, the needs of heat conservation necessitate low mass construction, whereas sound insulation needs high mass construction.'

Reading the two documents together could show up any number of discrepancies, although, as with ADL's RSDs, the details are not intended to show good construction practice, but simply the specific detail compliance with the relevant sound reduction elements.

However, even within the new document there are confusing details.

Diagram 4.2 (Clause 4.24) is a curiously scaled comparison between in situ and purpose-built drylining on masonry. Improvements need to be made to many of the diagrams, not least the unintelligible diagrams 0-1 to 0-3 in the opening section, to make the document more readable, and discrepancies between this and the current regulations should be highlighted. For example, the independent ceiling detail - shown as Floor Treatment 1 (Diagram 4.3) - now insists on 125mm between the top of the ceiling layer and the bottom of the separate soffit above, instead of the current gap of 100mm.

This tendency not to highlight changes is annoying, and will inevitably lead to needless errors in the future by architects not remembering, or realising, that they need to check.

NOISE FROM ABOVE

About 10 years ago, I was a site architect for a conversion of an old warehouse in the North East into luxury flats, writes David Pickering.

Everything went well; the contractor was diligent, we had a dour permanent clerk of works, a hands-on client's agent, and regular visits from the financial guarantor/certification body.

Before completing a couple of the flats, all five of us, together with several tradesmen, walked around to identify possible areas of sound transmission between floors, walls, ducts, etc and to agree on the necessary practical detailing and workmanship standards on site to comply with regulatory guidance.

On practical completion, all of the flats were let. Five months later, we were called out by a resident to investigate her complaints that she could hear people upstairs. We stood in silence as a 20-stone brickie was dispatched to march about upstairs in hob-nailed boots.When he reappeared, we all assumed that he had gone to the wrong flat because we had heard nothing. It was when the complainant then said that she could hear voices in her bedroom, while we all stood in her living room, that we realised that she was potty. But after making a fuss, within 10 days, everyone in the block was complaining of noise problems.

After loads of inspections, nobody knew what the problem was, or the solution, or who's liability it was. In fact, no one could really work out if there was a problem at all. In the end, we resolved to visit each resident saying that, in order to detect the real cause of the problem, all flats would have to be stripped back to the original building shell and redone. Given that every resident had just finished decorating, we heard no more about it.

Maybe this is what it means in ADE: 2003, Clause 1.35 where it states that 'once a dwelling-house, flat or room for residential purposes is occupied, any action affecting it should be a matter for local negotiation'.

TESTING TIME

The BRE Information Paper IP14/02 'Dealing with poor sound insulation between new dwellings' published in November 2002, one month before Approved Document E:2003 (ADE:2003) was published, sets out procedures to rectify faults giving rise to inadequate sound insulation resulting from poor construction or workmanship.

Given that ADE:2003 includes a requirement for pre-completion testing, and that pin-pointing the exact location of sound leakage is notoriously difficult, this BRE guidance document is a handy, though simplistic guide and is referred to in ADE:2003, Clause 1.37. The only discrepancy seems to be that IP14/02 quotes a sound insulation margin of failure in tests as 'up to 5dB'whereas ADE:2003 suggests 'no more than 6dB'.

In Approved Document L (ADL), clients can check over the contractor's completed work with a thermographic survey or smoke test. While the ODPM says that the need for ADE:2003 precompletion testing may be phased out in favour of reliance on RSDs, the contractor and/or architect may decide to take on the liability and cost of ensuring that all has reasonably been done to deal with sound transfer - one of the more subjective construction complaints. However, it will always be a case of discovery after the event and remedial treatment will be difficult and expensive.

The other difficulty is that although ADE:2003 refers to pre-completion testing, this is meant in a contractual rather than construction sense, since elements or units cannot be acoustically tested prior to the building being completed.On the other hand, in contractual terms, the completion certificate can be withheld if non-compliance is shown.Testing must be done by a UKAS accredited body.

Pre-completion testing, which comes into force in January 2004 for new houses and flats, can be avoided if the building is constructed in accordance with Robust Standard Details (RSDs). These are being drawn up by the House Builders Federation and the date of enforcement is six months later than the implementation of ADE:2003 to give them time to be completed, tested and checked.

However, since pre-completion testing (and BRE IP14/02) deals with discrepancies of workmanship, compliance with RSDs will not necessarily translate into the way things are built on site precisely because of poor workmanship. It is all a bit of a catch-22.

The BRE's IP14/02 suggests some likely causes of failure - and in typical wise-after-the-event troubleshooting, suggests remedial action - some more constructive than others. One example reads: 'Problem: Lower than expected airborne sound insulation (through separating walls) Probable cause: Excessive sound transmission through separating walls Solution: Rectify construction error.'

Very helpful. Thank you.

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