Poor sound insulation is an increasing problem with new homes. It is worse and more common in timber frame construction.
Sound insulation for internal soil vent pipes (SVP) is required in the NHBC standards under 8.1 S8 (C), which states:
"Sound insulation should be provided for soil pipes passing through habitable parts of dwellings." It requires 25mm thick plasterboard to the boxing with the pipe wrapped in a minimum, 25mm thick sound insulating material.
It is easy to check this, make a small say 25mm hole in the boxing and measure the board thickness.
Push the tape measure or small stick in the hole and scrape the pipe.
The stick should have traces of insulation on it if insulation is installed. If this is not the case then you can claim under the warranty as NHBC standards have clearly not been followed.
Building Regulations Part E state:
"E1 Dwelling houses, flats and rooms for residential purposes shall be designed and constructed in such a way that they provide reasonable resistance to sound from other parts of the same building and from adjoining buildings.
E2 Dwelling houses, flats and rooms for residential purposes shall be designed and constructed in such a way that:
(a) internal walls between a bedroom or a room containing a water closet, and other rooms; and
(b) internal floors
provide reasonable resistance to sound. " It can be seen that both E1 and E2 apply to residential dwellings.
The NHBC, in this case also responsible for Building Control, should realise that compliance of both E1 and E2 is required and as far as I can see, no distinction is made about the source of sound or how it is transmitted be it airborne or impact.
Regarding the use of Robust Details, these do allow the builder to avoid sound testing.
However, the robust details are designed to ensure compliance.
If the work has not been carried out fully and to the standards required in the robust detail(s) and a sound test proves this, remedial works would be required to rectify the failure to meet Part E of the Building Regulations and also therefore, the NHBC standards in my opinion.
It beggars belief that Barratt would claim that a failed sound test could be explained away as being caused by flanking sound.
Whilst this can be a cause of failure, measures should have been incorporated in the design and construction to limit and prevent flanking sound transfer.
To expect a new home to fail a sound test does not inspire confidence in both the quality of construction or the effectiveness of sound insulation in a Barratt new home.
To take this further, you need to do some investigative work.
It would be useful if you could get hold of the design drawings and the Robust Details your home is allegedly to be built to. An independent sound test may also be required to support your claim.
Despite your concerns, your best chance for a favourable outcome is via an NHBC warranty claim.
If you are unhappy with the service you have received from Barratt, you can make a complaint under the
Consumer Code for Homebuilders.
Be sure to fill in your HBF new home Consumer Satisfaction Survey accordingly too!
Barratt make a big deal about their five star rating.