How can I soundproof my walls?

The short answer is that 100% sound reduction between two semis is impossible. There are a number of measures you can carry out which will improve matters, but they are unlikely to solve your particular problem.

Have a look at robustdetails.com, where there are lots of examples of constructions used for delivering excellent soundproofing between dwellings. If you were building these semis new, the current Building Regulations would point you towards using one of these robust details which would provide soundproofing to the entire party wall to a level of around 45-50 decibels (dB).

That means that noises of this level (normal conversation, TV or radio) would be completely inaudible in the adjacent room of the neighbouring house. But for louder noises, this level of soundproofing wouldn’t be able to completely mask the sound — it would simply reduce it by 45-50dB. So if you were making a noise measuring, say, 80 or 90dB (which it sounds like you could easily be doing), then an awful lot of this noise would still be able to penetrate through the party wall into your neighbour’s house.

Now bear in mind, it is much harder to soundproof an existing house than it is to build one that way from scratch. Just adding more and more soundproofing elements to the room’s walls would never be enough, because sound travels by other routes as well, such as via the floor joist void, the loft void, and in and out of the doors and windows, not to mention via features like shared chimneys — common in your style of house. Even if you were to build a new separating wall, it would only provide a partial improvement. So, the hope that you might be able to soundproof the party wall to such an extent that you could make whatever sounds you liked and it wouldn’t penetrate into the neighbour’s house is completely unrealistic. But that’s not to say that you couldn’t carry out a number of improvements that would greatly help matters. A few simple measures you could take include:

Installing thick carpet on the floor, preferably with acoustic underlay (check out Acoustilay)

Installing secondary glazing – it’s better than ordinary double glazed units for soundproofing – together with really thick curtains

Building cupboards or bookcases against the party wall and filling them with a library load of heavy books, or your old vinyl collection — anything heavy will absorb sound pretty well

It’s important to note that the sound energy from lowfrequency sounds tends to travel directly through materials like brick and timber. The best way of reducing these transmissions is to isolate them from the structure — so don’t fix bass speakers to walls or floors, but place them on stands or on acoustic matting.

Finally, don’t kid yourself that your neighbours will be unaware of your loud all-night music sessions!