Soundproofing a party wall and flanking noise

Noise from neighbours through any party wall, particularly at night is a particular problem that affects many people.  Noise at night is always difficult to address because your normal background noises are usually switched off and when you are trying to get to sleep, noise from elsewhere can make it difficult.  Noise that is intermittent is the worst kind because it is not so easy to get used to whereas, noise that is more constant such as outside traffic is more easy to get used to and over a short period of time, is no longer noticeable in many cases.

What can be done about it?  Well this article is to deal with noisy neighbours so will involve the noise heard from the other side of a party wall and how to soundproof a party wall by stopping flanking noise.  We will deal with outside noise in another article.

Now for the neighbour noise.  Obviously the first thing that should be done is talk to them to explain the noise problem that is being heard.  The best way to do this is to invite them round for a cup of tea or something stronger then bring up the subject.  If you can replicate the sounds that are being heard from your side of the wall for your neighbour to hear, they would then have a greater understanding of the noise problem and hopefully, be more amenable to doing something about it so that your peace and tranquillity are restored.  The last thing that should be done is to go hammering on their door because the noise is so upsetting.  That would only antagonise them and make them less likely to co-operate.  Co-operation is always more successful than confrontation.  If all else fails then soundproofing is your last resort.  If the property is pre-war with solid structural walls then any soundproofing measures will be more effective but if the walls are cavity walls with lightweight internal blocks then flanking noise is likely to be a problem.  This is when noise flanks around the noise barrier and in the case of cavity walls, through the lightweight blocks and the cavity from one side of the wall to the other.  If the cavity has been filled with foam type cavity wall insulation the problem will still be evident but if the cavity has been filled with blown mineral wool, this will act as a sound absorber and the flanking noise will be less noticeable.  Flanking noise can also penetrate through the floors and ceilings if they are timber joist supported so before any work is started to soundproof the party wall, steps must be taken to reduce the flanking noise coming through the floor and ceiling.

Starting with the floor, if the floorboards are parallel with the wall then they will be easier to take up and only about four feet or 1.25 metres need to be removed to gain access to the joists.  Once the floorboards have been removed, check for gaps where the joists are fitted into the party wall because gaps will allow any noise to penetrate from one side to the other more easily.  If any gaps are found and they are simply small gaps then seal them with our flexible Acoustic Sealer but if the gaps are larger then they will have to be sealed with a sand/cement mixture.  Once the joists are suitably sealed in the party wall, install as a loose fit, 100mm of AMW100 Acoustic Mineral Wool between the joists.  AMW100 is supplied in slabs 1200 x 600 so they should be cut with a sharp knife so that you have a piece that is 1200mm long by just under the width of the joists then insert it so that one end is butted right up to the party wall.  Offcuts can be used in the same way so there is no wastage.  When complete replace the floor boards and screw them down.  However, if the floorboards are perpendicular to the party wall then the joists will be parallel and so not so easy to remove a small section of the floorboards.  So to compensate for this leave the floorboards alone and overlay with a double thickness of 2mm SBM5 Soundproofing Mat followed with a layer of polythene to contain any potential smells from this recycled sound insulation.  Although smells are not usually a problem, because the sound insulation is produced from recycled materials some times a smell is evident and although not noxious, will not be desirable so the polythene will seal it in.

Now for the ceiling.  If the ceiling is a top floor bedroom ceiling then it should be possible to check in the loft to see if the joists are correctly sealed into the party wall and if not, can be sealed as described earlier.  If the joists are in the other direct and parallel to the wall then sound leakage will not be so much of a problem and it will be just the flanking noise to deal with and that can be addressed from below.  From below all you have to do is screw up a 15mm layer of high density Acoustic Plasterboard with our 1mm SoundBlocker Membrane sandwiched between the new and old layers of plasterboard to break up the mass of the ceiling thus enhancing the noise blocking properties of the ceiling.

OK so now flanking noise through the floor and ceiling have been addressed you may wish to do something about flanking noise through the external structural wall if that is an issue and for this I suggest you fit our Thin Wall Soundproofing System.  This system is only 45mm thick or 50mm if 15mm Acoustic Plasterboard is used and should be applied over the entire wall surface.  More information on our Thin Wall Soundproofing System can be viewed on our web site via the following link https://www.keepitquiet.co.uk/thin-wall-soundproofing-system.html

Flanking noise round a party wall has now been covered in this Blog.  Keep your eye out for the next article that will be published shortly on the soundproofing methods that can be used to soundproof a party wall.  For more information on how to soundproof a party wall, or for any other of our soundproofing materials and products, go to the domestic side of our web site www.keepitquiet.co.uk