Insulation is sometimes installed close to a party wall for soundproofing. An expert should identify the source of the noise and also how the noise is being transmitted before any soundproofing work is carried. Noise can be ‘airborne’ through it is more common for it to occur through a wall, roof or floor structure. So, soundproofing may be used to help reduce the transfer of noise.
In certain situations, party wall insulation is made effective by simply placing it adjacent to the party wall but not fixed in position and then a structure is brought into place to hide it. The key to good insulation is density, which you ought to consider when deciding on which material to use.
The provision of party wall insulation may be regarded as ‘notifiable’ under the Act, as case law has proven that even disturbing the plaster on a wall can be relevant to the Party Wall Act. So, by carrying out these works, the party wall needs to be cut into and so a Notice will need to be served. The Adjoining Owner(s) will need to be given the opportunity to respond to the Notice.
It depends on the work. Internally insulating your own side of a party wall – battens, insulated plasterboard or a stud lining fixed to your own leaf – does not normally require a party wall notice, because you are not cutting into or interfering with the shared structure. The Act is engaged when the work goes further: cutting into the wall to insert insulation, fixing to the neighbour’s side, raising or thickening the wall, or installing external wall insulation that oversails the boundary. In those cases Section 2 of the Party Wall etc. Act 1996 applies and written notice must be served on the adjoining owner before work starts. Getting this wrong can mean an injunction stopping your project mid-build, so it is worth confirming the position before your installer begins.
If your insulation project does trigger the Act, the process is manageable: serve a valid notice (we can arrange this), and if your neighbour consents in writing the work can proceed, usually protected by a photographic schedule of condition. If they dissent, a party wall surveyor – or one for each side – prepares an award setting out how and when the work happens. Kingston Surveyors arranges RICS party wall surveyors across London for insulation-related notices and awards, with fixed fees agreed upfront; see our guide to party wall surveyor costs for typical figures. Call 0204 579 8270 for a free, same-day answer on whether your insulation plans need a notice at all.
