There can be a host of reasons why a partition might pass or fail a sound insulation test. We have put together a list of a few and explain how to avoid issues arising on your sites.

1 – Design

Poor acoustic design of party walls and floors as well as junction details will affect the on-site performance of the partition tested. Here are some examples:

  1. High number of braces connecting the leaves of lightweight party walls. We would recommend studs no closer than 600mm centres, braced every 1200mm vertically.2. Wrong wall ties specified for a masonry party wall. “Type A” wall ties are recommended for reliable acoustic performance.

3. No resilience to impact sound in the party floor build-up (e.g. missing resilient layer):

4. Junction between party wall and façade – inner leaf of the façade running continuously and uninterrupted from one side to the other of the party wall:

5. Missing flanking strips at the perimeter of the floating screed:

2 . Workmanship

Although the design may be acoustically sound in principle, it is crucial to avoid mistakes during the construction process. Some examples of common workmanship issues are provided below:

  1. Mortar dropped on wall ties on masonry party wall. This bridges the two leaves and reduces the sound insulation performance of the partition. (Image taken from Robust Details website).

2. Bridging of the resilient layer and/or flanking strips (see junction screed with curtain walling below – the gap between the two was filled with solid material):

3. Missing mastic at the junction between partitions:

4. Resilient bars incorrectly installed: see picture below showing resilient bars installed backwards on plywood.

5. Wrong material used on site. For example when multiple types of plasterboard are used around the site, these can easily be mixed up and installed in the wrong area (e.g. 12.5mm installed instead of the 15mm board).

3 . Site Conditions during Testing

Even if the design and workmanship are correct, there is still a risk of delayed or failed sound insulation tests due to unsuitable site conditions. Testing results can be affected by:

  1. Site not ready for sound testing (e.g.  too early stages for the testing).
  2. Missing internal doors or doors seals.
  3. Resilient layer or floor finishing not installed yet.
  4. Too much noise generated on-site by construction activities.
  5. Other trades on site affecting the testing procedures.

4 . Properly qualified testing body

The sound testing body must be registered with ANC or UKAS. This ensures that the standard procedures are followed and building control will accept the results of the testing.

It is also important that the testing is carried out with suitable and calibrated equipment. Registration with ANC or UKAS guarantees this.

If the testing body is not qualified and equipped, then the test results may be not compliant with requirements and rejected by Building Control leading to expensive retests.

Cheaper quotes do not always equate to saving in the long run!

5. That’s it…but what if the occupant complains?

Occupants have their own expectations regarding sound insulation between properties. If the occupant’s neighbours are behaving reasonably but they subsequently raise complaints regarding perceived “poor sound insulation performance” of their party wall, then it could be considered that the partition has “unofficially” failed to meet the requirements. In our experience, 9 times out of 10 these complaints are due to low background noise levels within the dwellings making any other sound more audible. Wherever possible, It is important for your consultant to take the internal noise environment at the site into account in the acoustic design of the partitions.

It could even be the case that the specific partition in question passed its sound test and you have obtained the appropriate certification.  In our experience, due to the other factors outlined above, meeting the minimum building regulations requirements doesn’t necessarily mean that noise from neighbouring properties will be inaudible and complaints can still occur.  See our previous mail-out here.

Top Tips for avoiding the above 5 reasons for sound testing failure

  1. Involve an Acoustics Consultant on the project at early design stages;
  2. Ensure that site team adopts and understands the design details;
  3. Seek advice from the Acoustics Consultant with regards to the required site conditions before the on-site testing;
  4. Ensure that the testing body carrying out the tests is fully equipped and qualified
  5. Take the internal acoustic environment into account.